-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | A compatibility layer for base
--   
--   Provides functions available in later versions of <tt>base</tt> to a
--   wider range of compilers, without requiring you to use CPP pragmas in
--   your code. See the <a>README</a> for what is covered. Also see the
--   <a>changelog</a> for recent changes.
--   
--   Note that <tt>base-compat</tt> does not add any orphan instances.
--   There is a separate package, <tt><a>base-orphans</a></tt>, for that.
--   
--   In addition, <tt>base-compat</tt> does not backport any data types or
--   type classes. See <tt><a>this section of the README</a></tt> for more
--   info.
--   
--   <tt>base-compat</tt> is designed to have zero dependencies. For a
--   version of <tt>base-compat</tt> that depends on compatibility
--   libraries for a wider support window, see the
--   <tt><a>base-compat-batteries</a></tt> package. Most of the modules in
--   this library have the same names as in <tt>base-compat-batteries</tt>
--   to make it easier to switch between the two. There also exist versions
--   of each module with the suffix <tt>.Repl</tt>, which are distinct from
--   anything in <tt>base-compat-batteries</tt>, to allow for easier use in
--   GHCi.
@package base-compat
@version 0.10.4

module Control.Concurrent.Compat

-- | Fork a thread and call the supplied function when the thread is about
--   to terminate, with an exception or a returned value. The function is
--   called with asynchronous exceptions masked.
--   
--   <pre>
--   forkFinally action and_then =
--     mask $ \restore -&gt;
--       forkIO $ try (restore action) &gt;&gt;= and_then
--   </pre>
--   
--   This function is useful for informing the parent when a child
--   terminates, for example.
forkFinally :: () => IO a -> Either SomeException a -> IO () -> IO ThreadId

-- | Like <a>forkIOWithUnmask</a>, but the child thread is a bound thread,
--   as with <a>forkOS</a>.
forkOSWithUnmask :: forall a. () => IO a -> IO a -> IO () -> IO ThreadId


-- | Reexports <a>Control.Concurrent.Compat</a> from a globally unique
--   namespace.
module Control.Concurrent.Compat.Repl

module Control.Concurrent.MVar.Compat

-- | Like <a>withMVar</a>, but the <tt>IO</tt> action in the second
--   argument is executed with asynchronous exceptions masked.
withMVarMasked :: () => MVar a -> a -> IO b -> IO b


-- | Reexports <a>Control.Concurrent.MVar.Compat</a> from a globally unique
--   namespace.
module Control.Concurrent.MVar.Compat.Repl

module Control.Exception.Compat

-- | If the first argument evaluates to <a>True</a>, then the result is the
--   second argument. Otherwise an <tt>AssertionFailed</tt> exception is
--   raised, containing a <a>String</a> with the source file and line
--   number of the call to <a>assert</a>.
--   
--   Assertions can normally be turned on or off with a compiler flag (for
--   GHC, assertions are normally on unless optimisation is turned on with
--   <tt>-O</tt> or the <tt>-fignore-asserts</tt> option is given). When
--   assertions are turned off, the first argument to <a>assert</a> is
--   ignored, and the second argument is returned as the result.
assert :: () => Bool -> a -> a

-- | When invoked inside <a>mask</a>, this function allows a masked
--   asynchronous exception to be raised, if one exists. It is equivalent
--   to performing an interruptible operation (see #interruptible), but
--   does not involve any actual blocking.
--   
--   When called outside <a>mask</a>, or inside <a>uninterruptibleMask</a>,
--   this function has no effect.
allowInterrupt :: IO ()

-- | Sometimes you want to catch two different sorts of exception. You
--   could do something like
--   
--   <pre>
--   f = expr `catch` \ (ex :: ArithException) -&gt; handleArith ex
--            `catch` \ (ex :: IOException)    -&gt; handleIO    ex
--   </pre>
--   
--   However, there are a couple of problems with this approach. The first
--   is that having two exception handlers is inefficient. However, the
--   more serious issue is that the second exception handler will catch
--   exceptions in the first, e.g. in the example above, if
--   <tt>handleArith</tt> throws an <tt>IOException</tt> then the second
--   exception handler will catch it.
--   
--   Instead, we provide a function <a>catches</a>, which would be used
--   thus:
--   
--   <pre>
--   f = expr `catches` [Handler (\ (ex :: ArithException) -&gt; handleArith ex),
--                       Handler (\ (ex :: IOException)    -&gt; handleIO    ex)]
--   </pre>
catches :: () => IO a -> [Handler a] -> IO a

-- | You need this when using <a>catches</a>.
data Handler a
[Handler] :: Handler a

-- | Like <a>bracket</a>, but only performs the final action if there was
--   an exception raised by the in-between computation.
bracketOnError :: () => IO a -> a -> IO b -> a -> IO c -> IO c

-- | A variant of <a>bracket</a> where the return value from the first
--   computation is not required.
bracket_ :: () => IO a -> IO b -> IO c -> IO c

-- | A specialised variant of <a>bracket</a> with just a computation to run
--   afterward.
finally :: () => IO a -> IO b -> IO a

-- | When you want to acquire a resource, do some work with it, and then
--   release the resource, it is a good idea to use <a>bracket</a>, because
--   <a>bracket</a> will install the necessary exception handler to release
--   the resource in the event that an exception is raised during the
--   computation. If an exception is raised, then <a>bracket</a> will
--   re-raise the exception (after performing the release).
--   
--   A common example is opening a file:
--   
--   <pre>
--   bracket
--     (openFile "filename" ReadMode)
--     (hClose)
--     (\fileHandle -&gt; do { ... })
--   </pre>
--   
--   The arguments to <a>bracket</a> are in this order so that we can
--   partially apply it, e.g.:
--   
--   <pre>
--   withFile name mode = bracket (openFile name mode) hClose
--   </pre>
bracket :: () => IO a -> a -> IO b -> a -> IO c -> IO c

-- | Like <a>finally</a>, but only performs the final action if there was
--   an exception raised by the computation.
onException :: () => IO a -> IO b -> IO a

-- | A variant of <a>try</a> that takes an exception predicate to select
--   which exceptions are caught (c.f. <a>catchJust</a>). If the exception
--   does not match the predicate, it is re-thrown.
tryJust :: Exception e => e -> Maybe b -> IO a -> IO Either b a

-- | Similar to <a>catch</a>, but returns an <a>Either</a> result which is
--   <tt>(<a>Right</a> a)</tt> if no exception of type <tt>e</tt> was
--   raised, or <tt>(<a>Left</a> ex)</tt> if an exception of type
--   <tt>e</tt> was raised and its value is <tt>ex</tt>. If any other type
--   of exception is raised than it will be propogated up to the next
--   enclosing exception handler.
--   
--   <pre>
--   try a = catch (Right `liftM` a) (return . Left)
--   </pre>
try :: Exception e => IO a -> IO Either e a

-- | This function maps one exception into another as proposed in the paper
--   "A semantics for imprecise exceptions".
mapException :: (Exception e1, Exception e2) => e1 -> e2 -> a -> a

-- | A version of <a>catchJust</a> with the arguments swapped around (see
--   <a>handle</a>).
handleJust :: Exception e => e -> Maybe b -> b -> IO a -> IO a -> IO a

-- | A version of <a>catch</a> with the arguments swapped around; useful in
--   situations where the code for the handler is shorter. For example:
--   
--   <pre>
--   do handle (\NonTermination -&gt; exitWith (ExitFailure 1)) $
--      ...
--   </pre>
handle :: Exception e => e -> IO a -> IO a -> IO a

-- | The function <a>catchJust</a> is like <a>catch</a>, but it takes an
--   extra argument which is an <i>exception predicate</i>, a function
--   which selects which type of exceptions we're interested in.
--   
--   <pre>
--   catchJust (\e -&gt; if isDoesNotExistErrorType (ioeGetErrorType e) then Just () else Nothing)
--             (readFile f)
--             (\_ -&gt; do hPutStrLn stderr ("No such file: " ++ show f)
--                       return "")
--   </pre>
--   
--   Any other exceptions which are not matched by the predicate are
--   re-raised, and may be caught by an enclosing <a>catch</a>,
--   <a>catchJust</a>, etc.
catchJust :: Exception e => e -> Maybe b -> IO a -> b -> IO a -> IO a

-- | A pattern match failed. The <tt>String</tt> gives information about
--   the source location of the pattern.
newtype PatternMatchFail
PatternMatchFail :: String -> PatternMatchFail

-- | A record selector was applied to a constructor without the appropriate
--   field. This can only happen with a datatype with multiple
--   constructors, where some fields are in one constructor but not
--   another. The <tt>String</tt> gives information about the source
--   location of the record selector.
newtype RecSelError
RecSelError :: String -> RecSelError

-- | An uninitialised record field was used. The <tt>String</tt> gives
--   information about the source location where the record was
--   constructed.
newtype RecConError
RecConError :: String -> RecConError

-- | A record update was performed on a constructor without the appropriate
--   field. This can only happen with a datatype with multiple
--   constructors, where some fields are in one constructor but not
--   another. The <tt>String</tt> gives information about the source
--   location of the record update.
newtype RecUpdError
RecUpdError :: String -> RecUpdError

-- | A class method without a definition (neither a default definition, nor
--   a definition in the appropriate instance) was called. The
--   <tt>String</tt> gives information about which method it was.
newtype NoMethodError
NoMethodError :: String -> NoMethodError

-- | An expression that didn't typecheck during compile time was called.
--   This is only possible with -fdefer-type-errors. The <tt>String</tt>
--   gives details about the failed type check.
newtype TypeError
TypeError :: String -> TypeError

-- | Thrown when the runtime system detects that the computation is
--   guaranteed not to terminate. Note that there is no guarantee that the
--   runtime system will notice whether any given computation is guaranteed
--   to terminate or not.
data NonTermination
NonTermination :: NonTermination

-- | Thrown when the program attempts to call <tt>atomically</tt>, from the
--   <tt>stm</tt> package, inside another call to <tt>atomically</tt>.
data NestedAtomically
NestedAtomically :: NestedAtomically

-- | <a>throwTo</a> raises an arbitrary exception in the target thread (GHC
--   only).
--   
--   Exception delivery synchronizes between the source and target thread:
--   <a>throwTo</a> does not return until the exception has been raised in
--   the target thread. The calling thread can thus be certain that the
--   target thread has received the exception. Exception delivery is also
--   atomic with respect to other exceptions. Atomicity is a useful
--   property to have when dealing with race conditions: e.g. if there are
--   two threads that can kill each other, it is guaranteed that only one
--   of the threads will get to kill the other.
--   
--   Whatever work the target thread was doing when the exception was
--   raised is not lost: the computation is suspended until required by
--   another thread.
--   
--   If the target thread is currently making a foreign call, then the
--   exception will not be raised (and hence <a>throwTo</a> will not
--   return) until the call has completed. This is the case regardless of
--   whether the call is inside a <a>mask</a> or not. However, in GHC a
--   foreign call can be annotated as <tt>interruptible</tt>, in which case
--   a <a>throwTo</a> will cause the RTS to attempt to cause the call to
--   return; see the GHC documentation for more details.
--   
--   Important note: the behaviour of <a>throwTo</a> differs from that
--   described in the paper "Asynchronous exceptions in Haskell"
--   (<a>http://research.microsoft.com/~simonpj/Papers/asynch-exns.htm</a>).
--   In the paper, <a>throwTo</a> is non-blocking; but the library
--   implementation adopts a more synchronous design in which
--   <a>throwTo</a> does not return until the exception is received by the
--   target thread. The trade-off is discussed in Section 9 of the paper.
--   Like any blocking operation, <a>throwTo</a> is therefore interruptible
--   (see Section 5.3 of the paper). Unlike other interruptible operations,
--   however, <a>throwTo</a> is <i>always</i> interruptible, even if it
--   does not actually block.
--   
--   There is no guarantee that the exception will be delivered promptly,
--   although the runtime will endeavour to ensure that arbitrary delays
--   don't occur. In GHC, an exception can only be raised when a thread
--   reaches a <i>safe point</i>, where a safe point is where memory
--   allocation occurs. Some loops do not perform any memory allocation
--   inside the loop and therefore cannot be interrupted by a
--   <a>throwTo</a>.
--   
--   If the target of <a>throwTo</a> is the calling thread, then the
--   behaviour is the same as <a>throwIO</a>, except that the exception is
--   thrown as an asynchronous exception. This means that if there is an
--   enclosing pure computation, which would be the case if the current IO
--   operation is inside <a>unsafePerformIO</a> or
--   <a>unsafeInterleaveIO</a>, that computation is not permanently
--   replaced by the exception, but is suspended as if it had received an
--   asynchronous exception.
--   
--   Note that if <a>throwTo</a> is called with the current thread as the
--   target, the exception will be thrown even if the thread is currently
--   inside <a>mask</a> or <a>uninterruptibleMask</a>.
throwTo :: Exception e => ThreadId -> e -> IO ()

-- | Raise an <a>IOError</a> in the <a>IO</a> monad.
ioError :: () => IOError -> IO a

asyncExceptionFromException :: Exception e => SomeException -> Maybe e

asyncExceptionToException :: Exception e => e -> SomeException

-- | The thread is blocked on an <tt>MVar</tt>, but there are no other
--   references to the <tt>MVar</tt> so it can't ever continue.
data BlockedIndefinitelyOnMVar
BlockedIndefinitelyOnMVar :: BlockedIndefinitelyOnMVar

-- | The thread is waiting to retry an STM transaction, but there are no
--   other references to any <tt>TVar</tt>s involved, so it can't ever
--   continue.
data BlockedIndefinitelyOnSTM
BlockedIndefinitelyOnSTM :: BlockedIndefinitelyOnSTM

-- | There are no runnable threads, so the program is deadlocked. The
--   <tt>Deadlock</tt> exception is raised in the main thread only.
data Deadlock
Deadlock :: Deadlock

-- | This thread has exceeded its allocation limit. See
--   <a>setAllocationCounter</a> and <a>enableAllocationLimit</a>.
data AllocationLimitExceeded
AllocationLimitExceeded :: AllocationLimitExceeded

-- | Compaction found an object that cannot be compacted. Functions cannot
--   be compacted, nor can mutable objects or pinned objects. See
--   <a>compact</a>.
newtype CompactionFailed
CompactionFailed :: String -> CompactionFailed

-- | <a>assert</a> was applied to <a>False</a>.
newtype AssertionFailed
AssertionFailed :: String -> AssertionFailed

-- | Superclass for asynchronous exceptions.
data SomeAsyncException
[SomeAsyncException] :: SomeAsyncException

-- | Asynchronous exceptions.
data AsyncException

-- | The current thread's stack exceeded its limit. Since an exception has
--   been raised, the thread's stack will certainly be below its limit
--   again, but the programmer should take remedial action immediately.
StackOverflow :: AsyncException

-- | The program's heap is reaching its limit, and the program should take
--   action to reduce the amount of live data it has. Notes:
--   
--   <ul>
--   <li>It is undefined which thread receives this exception. GHC
--   currently throws this to the same thread that receives
--   <a>UserInterrupt</a>, but this may change in the future.</li>
--   <li>The GHC RTS currently can only recover from heap overflow if it
--   detects that an explicit memory limit (set via RTS flags). has been
--   exceeded. Currently, failure to allocate memory from the operating
--   system results in immediate termination of the program.</li>
--   </ul>
HeapOverflow :: AsyncException

-- | This exception is raised by another thread calling <a>killThread</a>,
--   or by the system if it needs to terminate the thread for some reason.
ThreadKilled :: AsyncException

-- | This exception is raised by default in the main thread of the program
--   when the user requests to terminate the program via the usual
--   mechanism(s) (e.g. Control-C in the console).
UserInterrupt :: AsyncException

-- | Exceptions generated by array operations
data ArrayException

-- | An attempt was made to index an array outside its declared bounds.
IndexOutOfBounds :: String -> ArrayException

-- | An attempt was made to evaluate an element of an array that had not
--   been initialized.
UndefinedElement :: String -> ArrayException

-- | Evaluate the argument to weak head normal form.
--   
--   <a>evaluate</a> is typically used to uncover any exceptions that a
--   lazy value may contain, and possibly handle them.
--   
--   <a>evaluate</a> only evaluates to <i>weak head normal form</i>. If
--   deeper evaluation is needed, the <tt>force</tt> function from
--   <tt>Control.DeepSeq</tt> may be handy:
--   
--   <pre>
--   evaluate $ force x
--   </pre>
--   
--   There is a subtle difference between <tt><a>evaluate</a> x</tt> and
--   <tt><a>return</a> <a>$!</a> x</tt>, analogous to the difference
--   between <a>throwIO</a> and <a>throw</a>. If the lazy value <tt>x</tt>
--   throws an exception, <tt><a>return</a> <a>$!</a> x</tt> will fail to
--   return an <a>IO</a> action and will throw an exception instead.
--   <tt><a>evaluate</a> x</tt>, on the other hand, always produces an
--   <a>IO</a> action; that action will throw an exception upon
--   <i>execution</i> iff <tt>x</tt> throws an exception upon
--   <i>evaluation</i>.
--   
--   The practical implication of this difference is that due to the
--   <i>imprecise exceptions</i> semantics,
--   
--   <pre>
--   (return $! error "foo") &gt;&gt; error "bar"
--   </pre>
--   
--   may throw either <tt>"foo"</tt> or <tt>"bar"</tt>, depending on the
--   optimizations performed by the compiler. On the other hand,
--   
--   <pre>
--   evaluate (error "foo") &gt;&gt; error "bar"
--   </pre>
--   
--   is guaranteed to throw <tt>"foo"</tt>.
--   
--   The rule of thumb is to use <a>evaluate</a> to force or handle
--   exceptions in lazy values. If, on the other hand, you are forcing a
--   lazy value for efficiency reasons only and do not care about
--   exceptions, you may use <tt><a>return</a> <a>$!</a> x</tt>.
evaluate :: () => a -> IO a

-- | Like <a>mask</a>, but the masked computation is not interruptible (see
--   <a>Control.Exception#interruptible</a>). THIS SHOULD BE USED WITH
--   GREAT CARE, because if a thread executing in
--   <a>uninterruptibleMask</a> blocks for any reason, then the thread (and
--   possibly the program, if this is the main thread) will be unresponsive
--   and unkillable. This function should only be necessary if you need to
--   mask exceptions around an interruptible operation, and you can
--   guarantee that the interruptible operation will only block for a short
--   period of time.
uninterruptibleMask :: () => forall a. () => IO a -> IO a -> IO b -> IO b

-- | Like <a>uninterruptibleMask</a>, but does not pass a <tt>restore</tt>
--   action to the argument.
uninterruptibleMask_ :: () => IO a -> IO a

-- | Executes an IO computation with asynchronous exceptions <i>masked</i>.
--   That is, any thread which attempts to raise an exception in the
--   current thread with <a>throwTo</a> will be blocked until asynchronous
--   exceptions are unmasked again.
--   
--   The argument passed to <a>mask</a> is a function that takes as its
--   argument another function, which can be used to restore the prevailing
--   masking state within the context of the masked computation. For
--   example, a common way to use <a>mask</a> is to protect the acquisition
--   of a resource:
--   
--   <pre>
--   mask $ \restore -&gt; do
--       x &lt;- acquire
--       restore (do_something_with x) `onException` release
--       release
--   </pre>
--   
--   This code guarantees that <tt>acquire</tt> is paired with
--   <tt>release</tt>, by masking asynchronous exceptions for the critical
--   parts. (Rather than write this code yourself, it would be better to
--   use <a>bracket</a> which abstracts the general pattern).
--   
--   Note that the <tt>restore</tt> action passed to the argument to
--   <a>mask</a> does not necessarily unmask asynchronous exceptions, it
--   just restores the masking state to that of the enclosing context. Thus
--   if asynchronous exceptions are already masked, <a>mask</a> cannot be
--   used to unmask exceptions again. This is so that if you call a library
--   function with exceptions masked, you can be sure that the library call
--   will not be able to unmask exceptions again. If you are writing
--   library code and need to use asynchronous exceptions, the only way is
--   to create a new thread; see <a>forkIOWithUnmask</a>.
--   
--   Asynchronous exceptions may still be received while in the masked
--   state if the masked thread <i>blocks</i> in certain ways; see
--   <a>Control.Exception#interruptible</a>.
--   
--   Threads created by <a>forkIO</a> inherit the <a>MaskingState</a> from
--   the parent; that is, to start a thread in the
--   <a>MaskedInterruptible</a> state, use <tt>mask_ $ forkIO ...</tt>.
--   This is particularly useful if you need to establish an exception
--   handler in the forked thread before any asynchronous exceptions are
--   received. To create a a new thread in an unmasked state use
--   <a>forkIOWithUnmask</a>.
mask :: () => forall a. () => IO a -> IO a -> IO b -> IO b

-- | Like <a>mask</a>, but does not pass a <tt>restore</tt> action to the
--   argument.
mask_ :: () => IO a -> IO a

-- | Returns the <a>MaskingState</a> for the current thread.
getMaskingState :: IO MaskingState

-- | Allow asynchronous exceptions to be raised even inside <a>mask</a>,
--   making the operation interruptible (see the discussion of
--   "Interruptible operations" in <a>Exception</a>).
--   
--   When called outside <a>mask</a>, or inside <a>uninterruptibleMask</a>,
--   this function has no effect.
interruptible :: () => IO a -> IO a

-- | A variant of <a>throw</a> that can only be used within the <a>IO</a>
--   monad.
--   
--   Although <a>throwIO</a> has a type that is an instance of the type of
--   <a>throw</a>, the two functions are subtly different:
--   
--   <pre>
--   throw e   `seq` x  ===&gt; throw e
--   throwIO e `seq` x  ===&gt; x
--   </pre>
--   
--   The first example will cause the exception <tt>e</tt> to be raised,
--   whereas the second one won't. In fact, <a>throwIO</a> will only cause
--   an exception to be raised when it is used within the <a>IO</a> monad.
--   The <a>throwIO</a> variant should be used in preference to
--   <a>throw</a> to raise an exception within the <a>IO</a> monad because
--   it guarantees ordering with respect to other <a>IO</a> operations,
--   whereas <a>throw</a> does not.
throwIO :: Exception e => e -> IO a

-- | This is the simplest of the exception-catching functions. It takes a
--   single argument, runs it, and if an exception is raised the "handler"
--   is executed, with the value of the exception passed as an argument.
--   Otherwise, the result is returned as normal. For example:
--   
--   <pre>
--   catch (readFile f)
--         (\e -&gt; do let err = show (e :: IOException)
--                   hPutStr stderr ("Warning: Couldn't open " ++ f ++ ": " ++ err)
--                   return "")
--   </pre>
--   
--   Note that we have to give a type signature to <tt>e</tt>, or the
--   program will not typecheck as the type is ambiguous. While it is
--   possible to catch exceptions of any type, see the section "Catching
--   all exceptions" (in <a>Control.Exception</a>) for an explanation of
--   the problems with doing so.
--   
--   For catching exceptions in pure (non-<a>IO</a>) expressions, see the
--   function <a>evaluate</a>.
--   
--   Note that due to Haskell's unspecified evaluation order, an expression
--   may throw one of several possible exceptions: consider the expression
--   <tt>(error "urk") + (1 `div` 0)</tt>. Does the expression throw
--   <tt>ErrorCall "urk"</tt>, or <tt>DivideByZero</tt>?
--   
--   The answer is "it might throw either"; the choice is
--   non-deterministic. If you are catching any type of exception then you
--   might catch either. If you are calling <tt>catch</tt> with type <tt>IO
--   Int -&gt; (ArithException -&gt; IO Int) -&gt; IO Int</tt> then the
--   handler may get run with <tt>DivideByZero</tt> as an argument, or an
--   <tt>ErrorCall "urk"</tt> exception may be propogated further up. If
--   you call it again, you might get a the opposite behaviour. This is ok,
--   because <a>catch</a> is an <a>IO</a> computation.
catch :: Exception e => IO a -> e -> IO a -> IO a

-- | Describes the behaviour of a thread when an asynchronous exception is
--   received.
data MaskingState

-- | asynchronous exceptions are unmasked (the normal state)
Unmasked :: MaskingState

-- | the state during <a>mask</a>: asynchronous exceptions are masked, but
--   blocking operations may still be interrupted
MaskedInterruptible :: MaskingState

-- | the state during <a>uninterruptibleMask</a>: asynchronous exceptions
--   are masked, and blocking operations may not be interrupted
MaskedUninterruptible :: MaskingState

-- | Exceptions that occur in the <tt>IO</tt> monad. An
--   <tt>IOException</tt> records a more specific error type, a descriptive
--   string and maybe the handle that was used when the error was flagged.
data IOException

-- | Any type that you wish to throw or catch as an exception must be an
--   instance of the <tt>Exception</tt> class. The simplest case is a new
--   exception type directly below the root:
--   
--   <pre>
--   data MyException = ThisException | ThatException
--       deriving Show
--   
--   instance Exception MyException
--   </pre>
--   
--   The default method definitions in the <tt>Exception</tt> class do what
--   we need in this case. You can now throw and catch
--   <tt>ThisException</tt> and <tt>ThatException</tt> as exceptions:
--   
--   <pre>
--   *Main&gt; throw ThisException `catch` \e -&gt; putStrLn ("Caught " ++ show (e :: MyException))
--   Caught ThisException
--   </pre>
--   
--   In more complicated examples, you may wish to define a whole hierarchy
--   of exceptions:
--   
--   <pre>
--   ---------------------------------------------------------------------
--   -- Make the root exception type for all the exceptions in a compiler
--   
--   data SomeCompilerException = forall e . Exception e =&gt; SomeCompilerException e
--   
--   instance Show SomeCompilerException where
--       show (SomeCompilerException e) = show e
--   
--   instance Exception SomeCompilerException
--   
--   compilerExceptionToException :: Exception e =&gt; e -&gt; SomeException
--   compilerExceptionToException = toException . SomeCompilerException
--   
--   compilerExceptionFromException :: Exception e =&gt; SomeException -&gt; Maybe e
--   compilerExceptionFromException x = do
--       SomeCompilerException a &lt;- fromException x
--       cast a
--   
--   ---------------------------------------------------------------------
--   -- Make a subhierarchy for exceptions in the frontend of the compiler
--   
--   data SomeFrontendException = forall e . Exception e =&gt; SomeFrontendException e
--   
--   instance Show SomeFrontendException where
--       show (SomeFrontendException e) = show e
--   
--   instance Exception SomeFrontendException where
--       toException = compilerExceptionToException
--       fromException = compilerExceptionFromException
--   
--   frontendExceptionToException :: Exception e =&gt; e -&gt; SomeException
--   frontendExceptionToException = toException . SomeFrontendException
--   
--   frontendExceptionFromException :: Exception e =&gt; SomeException -&gt; Maybe e
--   frontendExceptionFromException x = do
--       SomeFrontendException a &lt;- fromException x
--       cast a
--   
--   ---------------------------------------------------------------------
--   -- Make an exception type for a particular frontend compiler exception
--   
--   data MismatchedParentheses = MismatchedParentheses
--       deriving Show
--   
--   instance Exception MismatchedParentheses where
--       toException   = frontendExceptionToException
--       fromException = frontendExceptionFromException
--   </pre>
--   
--   We can now catch a <tt>MismatchedParentheses</tt> exception as
--   <tt>MismatchedParentheses</tt>, <tt>SomeFrontendException</tt> or
--   <tt>SomeCompilerException</tt>, but not other types, e.g.
--   <tt>IOException</tt>:
--   
--   <pre>
--   *Main&gt; throw MismatchedParentheses `catch` \e -&gt; putStrLn ("Caught " ++ show (e :: MismatchedParentheses))
--   Caught MismatchedParentheses
--   *Main&gt; throw MismatchedParentheses `catch` \e -&gt; putStrLn ("Caught " ++ show (e :: SomeFrontendException))
--   Caught MismatchedParentheses
--   *Main&gt; throw MismatchedParentheses `catch` \e -&gt; putStrLn ("Caught " ++ show (e :: SomeCompilerException))
--   Caught MismatchedParentheses
--   *Main&gt; throw MismatchedParentheses `catch` \e -&gt; putStrLn ("Caught " ++ show (e :: IOException))
--   *** Exception: MismatchedParentheses
--   </pre>
class (Typeable e, Show e) => Exception e
toException :: Exception e => e -> SomeException
fromException :: Exception e => SomeException -> Maybe e

-- | Render this exception value in a human-friendly manner.
--   
--   Default implementation: <tt><a>show</a></tt>.
displayException :: Exception e => e -> String

-- | This is thrown when the user calls <a>error</a>. The first
--   <tt>String</tt> is the argument given to <a>error</a>, second
--   <tt>String</tt> is the location.
data ErrorCall
ErrorCallWithLocation :: String -> String -> ErrorCall

-- | Arithmetic exceptions.
data ArithException
Overflow :: ArithException
Underflow :: ArithException
LossOfPrecision :: ArithException
DivideByZero :: ArithException
Denormal :: ArithException

RatioZeroDenominator :: ArithException

-- | The <tt>SomeException</tt> type is the root of the exception type
--   hierarchy. When an exception of type <tt>e</tt> is thrown, behind the
--   scenes it is encapsulated in a <tt>SomeException</tt>.
data SomeException
[SomeException] :: SomeException

-- | Throw an exception. Exceptions may be thrown from purely functional
--   code, but may only be caught within the <tt>IO</tt> monad.
throw :: forall (r :: RuntimeRep). forall (a :: TYPE r). forall e. Exception e => e -> a


-- | Reexports <a>Control.Exception.Compat</a> from a globally unique
--   namespace.
module Control.Exception.Compat.Repl

module Control.Monad.Compat

-- | The <a>Monad</a> class defines the basic operations over a
--   <i>monad</i>, a concept from a branch of mathematics known as
--   <i>category theory</i>. From the perspective of a Haskell programmer,
--   however, it is best to think of a monad as an <i>abstract datatype</i>
--   of actions. Haskell's <tt>do</tt> expressions provide a convenient
--   syntax for writing monadic expressions.
--   
--   Instances of <a>Monad</a> should satisfy the following laws:
--   
--   <ul>
--   <li><pre><a>return</a> a <a>&gt;&gt;=</a> k = k a</pre></li>
--   <li><pre>m <a>&gt;&gt;=</a> <a>return</a> = m</pre></li>
--   <li><pre>m <a>&gt;&gt;=</a> (\x -&gt; k x <a>&gt;&gt;=</a> h) = (m
--   <a>&gt;&gt;=</a> k) <a>&gt;&gt;=</a> h</pre></li>
--   </ul>
--   
--   Furthermore, the <a>Monad</a> and <a>Applicative</a> operations should
--   relate as follows:
--   
--   <ul>
--   <li><pre><a>pure</a> = <a>return</a></pre></li>
--   <li><pre>(<a>&lt;*&gt;</a>) = <a>ap</a></pre></li>
--   </ul>
--   
--   The above laws imply:
--   
--   <ul>
--   <li><pre><a>fmap</a> f xs = xs <a>&gt;&gt;=</a> <a>return</a> .
--   f</pre></li>
--   <li><pre>(<a>&gt;&gt;</a>) = (<a>*&gt;</a>)</pre></li>
--   </ul>
--   
--   and that <a>pure</a> and (<a>&lt;*&gt;</a>) satisfy the applicative
--   functor laws.
--   
--   The instances of <a>Monad</a> for lists, <a>Maybe</a> and <a>IO</a>
--   defined in the <a>Prelude</a> satisfy these laws.
class Applicative m => Monad (m :: * -> *)

-- | Sequentially compose two actions, passing any value produced by the
--   first as an argument to the second.
(>>=) :: Monad m => m a -> a -> m b -> m b

-- | Sequentially compose two actions, discarding any value produced by the
--   first, like sequencing operators (such as the semicolon) in imperative
--   languages.
(>>) :: Monad m => m a -> m b -> m b

-- | Inject a value into the monadic type.
return :: Monad m => a -> m a

-- | Fail with a message. This operation is not part of the mathematical
--   definition of a monad, but is invoked on pattern-match failure in a
--   <tt>do</tt> expression.
--   
--   As part of the MonadFail proposal (MFP), this function is moved to its
--   own class <tt>MonadFail</tt> (see <a>Control.Monad.Fail</a> for more
--   details). The definition here will be removed in a future release.
fail :: Monad m => String -> m a

-- | Monads that also support choice and failure.
class (Alternative m, Monad m) => MonadPlus (m :: * -> *)

-- | The identity of <a>mplus</a>. It should also satisfy the equations
--   
--   <pre>
--   mzero &gt;&gt;= f  =  mzero
--   v &gt;&gt; mzero   =  mzero
--   </pre>
--   
--   The default definition is
--   
--   <pre>
--   mzero = <a>empty</a>
--   </pre>
mzero :: MonadPlus m => m a

-- | An associative operation. The default definition is
--   
--   <pre>
--   mplus = (<a>&lt;|&gt;</a>)
--   </pre>
mplus :: MonadPlus m => m a -> m a -> m a


-- | Reexports <a>Control.Monad.Compat</a> from a globally unique
--   namespace.
module Control.Monad.Compat.Repl

module Control.Monad.Fail.Compat


-- | Reexports <a>Control.Monad.Fail.Compat</a> from a globally unique
--   namespace.
module Control.Monad.Fail.Compat.Repl

module Control.Monad.IO.Class.Compat


-- | Reexports <a>Control.Monad.IO.Class.Compat</a> from a globally unique
--   namespace.
module Control.Monad.IO.Class.Compat.Repl

module Control.Monad.ST.Lazy.Unsafe.Compat
unsafeInterleaveST :: () => ST s a -> ST s a
unsafeIOToST :: () => IO a -> ST s a


-- | Reexports <a>Control.Monad.ST.Lazy.Unsafe.Compat</a> from a globally
--   unique namespace.
module Control.Monad.ST.Lazy.Unsafe.Compat.Repl

module Control.Monad.ST.Unsafe.Compat

-- | <a>unsafeInterleaveST</a> allows an <a>ST</a> computation to be
--   deferred lazily. When passed a value of type <tt>ST a</tt>, the
--   <a>ST</a> computation will only be performed when the value of the
--   <tt>a</tt> is demanded.
unsafeInterleaveST :: () => ST s a -> ST s a

-- | Convert an <a>IO</a> action to an <a>ST</a> action. This relies on
--   <a>IO</a> and <a>ST</a> having the same representation modulo the
--   constraint on the type of the state.
unsafeIOToST :: () => IO a -> ST s a

-- | Convert an <a>ST</a> action to an <a>IO</a> action. This relies on
--   <a>IO</a> and <a>ST</a> having the same representation modulo the
--   constraint on the type of the state.
--   
--   For an example demonstrating why this is unsafe, see
--   <a>https://mail.haskell.org/pipermail/haskell-cafe/2009-April/060719.html</a>
unsafeSTToIO :: () => ST s a -> IO a


-- | Reexports <a>Control.Monad.ST.Unsafe.Compat</a> from a globally unique
--   namespace.
module Control.Monad.ST.Unsafe.Compat.Repl

module Data.Bifoldable.Compat


-- | Reexports <a>Data.Bifoldable.Compat</a> from a globally unique
--   namespace.
module Data.Bifoldable.Compat.Repl

module Data.Bifunctor.Compat


-- | Reexports <a>Data.Bifunctor.Compat</a> from a globally unique
--   namespace.
module Data.Bifunctor.Compat.Repl

module Data.Bitraversable.Compat


-- | Reexports <a>Data.Bitraversable.Compat</a> from a globally unique
--   namespace.
module Data.Bitraversable.Compat.Repl

module Data.Bits.Compat

-- | Default implementation for <a>bit</a>.
--   
--   Note that: <tt>bitDefault i = 1 <a>shiftL</a> i</tt>
bitDefault :: (Bits a, Num a) => Int -> a

-- | Default implementation for <a>testBit</a>.
--   
--   Note that: <tt>testBitDefault x i = (x .&amp;. bit i) /= 0</tt>
testBitDefault :: (Bits a, Num a) => a -> Int -> Bool

-- | Default implementation for <a>popCount</a>.
--   
--   This implementation is intentionally naive. Instances are expected to
--   provide an optimized implementation for their size.
popCountDefault :: (Bits a, Num a) => a -> Int

-- | Attempt to convert an <a>Integral</a> type <tt>a</tt> to an
--   <a>Integral</a> type <tt>b</tt> using the size of the types as
--   measured by <a>Bits</a> methods.
--   
--   A simpler version of this function is:
--   
--   <pre>
--   toIntegral :: (Integral a, Integral b) =&gt; a -&gt; Maybe b
--   toIntegral x
--     | toInteger x == y = Just (fromInteger y)
--     | otherwise        = Nothing
--     where
--       y = toInteger x
--   </pre>
--   
--   This version requires going through <a>Integer</a>, which can be
--   inefficient. However, <tt>toIntegralSized</tt> is optimized to allow
--   GHC to statically determine the relative type sizes (as measured by
--   <a>bitSizeMaybe</a> and <a>isSigned</a>) and avoid going through
--   <a>Integer</a> for many types. (The implementation uses
--   <a>fromIntegral</a>, which is itself optimized with rules for
--   <tt>base</tt> types but may go through <a>Integer</a> for some type
--   pairs.)
toIntegralSized :: (Integral a, Integral b, Bits a, Bits b) => a -> Maybe b


-- | Reexports <a>Data.Bits.Compat</a> from a globally unique namespace.
module Data.Bits.Compat.Repl

module Data.Bool.Compat

-- | Case analysis for the <a>Bool</a> type. <tt><a>bool</a> x y p</tt>
--   evaluates to <tt>x</tt> when <tt>p</tt> is <a>False</a>, and evaluates
--   to <tt>y</tt> when <tt>p</tt> is <a>True</a>.
--   
--   This is equivalent to <tt>if p then y else x</tt>; that is, one can
--   think of it as an if-then-else construct with its arguments reordered.
--   
--   <h4><b>Examples</b></h4>
--   
--   Basic usage:
--   
--   <pre>
--   &gt;&gt;&gt; bool "foo" "bar" True
--   "bar"
--   
--   &gt;&gt;&gt; bool "foo" "bar" False
--   "foo"
--   </pre>
--   
--   Confirm that <tt><a>bool</a> x y p</tt> and <tt>if p then y else
--   x</tt> are equivalent:
--   
--   <pre>
--   &gt;&gt;&gt; let p = True; x = "bar"; y = "foo"
--   
--   &gt;&gt;&gt; bool x y p == if p then y else x
--   True
--   
--   &gt;&gt;&gt; let p = False
--   
--   &gt;&gt;&gt; bool x y p == if p then y else x
--   True
--   </pre>
bool :: () => a -> a -> Bool -> a


-- | Reexports <a>Data.Bool.Compat</a> from a globally unique namespace.
module Data.Bool.Compat.Repl

module Data.Complex.Compat


-- | Reexports <a>Data.Complex.Compat</a> from a globally unique namespace.
module Data.Complex.Compat.Repl

module Data.Either.Compat

-- | Return <a>True</a> if the given value is a <a>Left</a>-value,
--   <a>False</a> otherwise.
--   
--   <h4><b>Examples</b></h4>
--   
--   Basic usage:
--   
--   <pre>
--   &gt;&gt;&gt; isLeft (Left "foo")
--   True
--   
--   &gt;&gt;&gt; isLeft (Right 3)
--   False
--   </pre>
--   
--   Assuming a <a>Left</a> value signifies some sort of error, we can use
--   <a>isLeft</a> to write a very simple error-reporting function that
--   does absolutely nothing in the case of success, and outputs "ERROR" if
--   any error occurred.
--   
--   This example shows how <a>isLeft</a> might be used to avoid pattern
--   matching when one does not care about the value contained in the
--   constructor:
--   
--   <pre>
--   &gt;&gt;&gt; import Control.Monad ( when )
--   
--   &gt;&gt;&gt; let report e = when (isLeft e) $ putStrLn "ERROR"
--   
--   &gt;&gt;&gt; report (Right 1)
--   
--   &gt;&gt;&gt; report (Left "parse error")
--   ERROR
--   </pre>
isLeft :: () => Either a b -> Bool

-- | Return <a>True</a> if the given value is a <a>Right</a>-value,
--   <a>False</a> otherwise.
--   
--   <h4><b>Examples</b></h4>
--   
--   Basic usage:
--   
--   <pre>
--   &gt;&gt;&gt; isRight (Left "foo")
--   False
--   
--   &gt;&gt;&gt; isRight (Right 3)
--   True
--   </pre>
--   
--   Assuming a <a>Left</a> value signifies some sort of error, we can use
--   <a>isRight</a> to write a very simple reporting function that only
--   outputs "SUCCESS" when a computation has succeeded.
--   
--   This example shows how <a>isRight</a> might be used to avoid pattern
--   matching when one does not care about the value contained in the
--   constructor:
--   
--   <pre>
--   &gt;&gt;&gt; import Control.Monad ( when )
--   
--   &gt;&gt;&gt; let report e = when (isRight e) $ putStrLn "SUCCESS"
--   
--   &gt;&gt;&gt; report (Left "parse error")
--   
--   &gt;&gt;&gt; report (Right 1)
--   SUCCESS
--   </pre>
isRight :: () => Either a b -> Bool

-- | Return the contents of a <a>Left</a>-value or a default value
--   otherwise.
--   
--   <h4><b>Examples</b></h4>
--   
--   Basic usage:
--   
--   <pre>
--   &gt;&gt;&gt; fromLeft 1 (Left 3)
--   3
--   
--   &gt;&gt;&gt; fromLeft 1 (Right "foo")
--   1
--   </pre>
fromLeft :: () => a -> Either a b -> a

-- | Return the contents of a <a>Right</a>-value or a default value
--   otherwise.
--   
--   <h4><b>Examples</b></h4>
--   
--   Basic usage:
--   
--   <pre>
--   &gt;&gt;&gt; fromRight 1 (Right 3)
--   3
--   
--   &gt;&gt;&gt; fromRight 1 (Left "foo")
--   1
--   </pre>
fromRight :: () => b -> Either a b -> b


-- | Reexports <a>Data.Either.Compat</a> from a globally unique namespace.
module Data.Either.Compat.Repl

module Data.Foldable.Compat


-- | Reexports <a>Data.Foldable.Compat</a> from a globally unique
--   namespace.
module Data.Foldable.Compat.Repl

module Data.Function.Compat

-- | <a>&amp;</a> is a reverse application operator. This provides
--   notational convenience. Its precedence is one higher than that of the
--   forward application operator <a>$</a>, which allows <a>&amp;</a> to be
--   nested in <a>$</a>.
--   
--   <pre>
--   &gt;&gt;&gt; 5 &amp; (+1) &amp; show
--   "6"
--   </pre>
(&) :: () => a -> a -> b -> b
infixl 1 &


-- | Reexports <a>Data.Function.Compat</a> from a globally unique
--   namespace.
module Data.Function.Compat.Repl

module Data.Functor.Compat

-- | The <a>Functor</a> class is used for types that can be mapped over.
--   Instances of <a>Functor</a> should satisfy the following laws:
--   
--   <pre>
--   fmap id  ==  id
--   fmap (f . g)  ==  fmap f . fmap g
--   </pre>
--   
--   The instances of <a>Functor</a> for lists, <a>Maybe</a> and <a>IO</a>
--   satisfy these laws.
class Functor (f :: * -> *)
fmap :: Functor f => a -> b -> f a -> f b

-- | Replace all locations in the input with the same value. The default
--   definition is <tt><a>fmap</a> . <a>const</a></tt>, but this may be
--   overridden with a more efficient version.
(<$) :: Functor f => a -> f b -> f a

-- | Flipped version of <a>&lt;$</a>.
--   
--   <h4><b>Examples</b></h4>
--   
--   Replace the contents of a <tt><tt>Maybe</tt> <tt>Int</tt></tt> with a
--   constant <tt>String</tt>:
--   
--   <pre>
--   &gt;&gt;&gt; Nothing $&gt; "foo"
--   Nothing
--   
--   &gt;&gt;&gt; Just 90210 $&gt; "foo"
--   Just "foo"
--   </pre>
--   
--   Replace the contents of an <tt><tt>Either</tt> <tt>Int</tt>
--   <tt>Int</tt></tt> with a constant <tt>String</tt>, resulting in an
--   <tt><tt>Either</tt> <tt>Int</tt> <tt>String</tt></tt>:
--   
--   <pre>
--   &gt;&gt;&gt; Left 8675309 $&gt; "foo"
--   Left 8675309
--   
--   &gt;&gt;&gt; Right 8675309 $&gt; "foo"
--   Right "foo"
--   </pre>
--   
--   Replace each element of a list with a constant <tt>String</tt>:
--   
--   <pre>
--   &gt;&gt;&gt; [1,2,3] $&gt; "foo"
--   ["foo","foo","foo"]
--   </pre>
--   
--   Replace the second element of a pair with a constant <tt>String</tt>:
--   
--   <pre>
--   &gt;&gt;&gt; (1,2) $&gt; "foo"
--   (1,"foo")
--   </pre>
($>) :: Functor f => f a -> b -> f b
infixl 4 $>

-- | <tt><a>void</a> value</tt> discards or ignores the result of
--   evaluation, such as the return value of an <a>IO</a> action.
--   
--   <h4><b>Examples</b></h4>
--   
--   Replace the contents of a <tt><tt>Maybe</tt> <tt>Int</tt></tt> with
--   unit:
--   
--   <pre>
--   &gt;&gt;&gt; void Nothing
--   Nothing
--   
--   &gt;&gt;&gt; void (Just 3)
--   Just ()
--   </pre>
--   
--   Replace the contents of an <tt><tt>Either</tt> <tt>Int</tt>
--   <tt>Int</tt></tt> with unit, resulting in an <tt><tt>Either</tt>
--   <tt>Int</tt> '()'</tt>:
--   
--   <pre>
--   &gt;&gt;&gt; void (Left 8675309)
--   Left 8675309
--   
--   &gt;&gt;&gt; void (Right 8675309)
--   Right ()
--   </pre>
--   
--   Replace every element of a list with unit:
--   
--   <pre>
--   &gt;&gt;&gt; void [1,2,3]
--   [(),(),()]
--   </pre>
--   
--   Replace the second element of a pair with unit:
--   
--   <pre>
--   &gt;&gt;&gt; void (1,2)
--   (1,())
--   </pre>
--   
--   Discard the result of an <a>IO</a> action:
--   
--   <pre>
--   &gt;&gt;&gt; mapM print [1,2]
--   1
--   2
--   [(),()]
--   
--   &gt;&gt;&gt; void $ mapM print [1,2]
--   1
--   2
--   </pre>
void :: Functor f => f a -> f ()

-- | Flipped version of <a>&lt;$&gt;</a>.
--   
--   <pre>
--   (<a>&lt;&amp;&gt;</a>) = <a>flip</a> <a>fmap</a>
--   </pre>
--   
--   <h4><b>Examples</b></h4>
--   
--   Apply <tt>(+1)</tt> to a list, a <a>Just</a> and a <a>Right</a>:
--   
--   <pre>
--   &gt;&gt;&gt; Just 2 &lt;&amp;&gt; (+1)
--   Just 3
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; [1,2,3] &lt;&amp;&gt; (+1)
--   [2,3,4]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; Right 3 &lt;&amp;&gt; (+1)
--   Right 4
--   </pre>
(<&>) :: Functor f => f a -> a -> b -> f b
infixl 1 <&>


-- | Reexports <a>Data.Functor.Compat</a> from a globally unique namespace.
module Data.Functor.Compat.Repl

module Data.Functor.Compose.Compat


-- | Reexports <a>Data.Functor.Compose.Compat</a> from a globally unique
--   namespace.
module Data.Functor.Compose.Compat.Repl

module Data.Functor.Const.Compat

-- | The <a>Const</a> functor.
newtype Const a (b :: k) :: forall k. () => * -> k -> *
Const :: a -> Const a
[getConst] :: Const a -> a


-- | Reexports <a>Data.Functor.Const.Compat</a> from a globally unique
--   namespace.
module Data.Functor.Const.Compat.Repl

module Data.Functor.Contravariant.Compat


-- | Reexports <a>Data.Functor.Contravariant.Compat</a> from a globally
--   unique namespace.
module Data.Functor.Contravariant.Compat.Repl

module Data.Functor.Identity.Compat


-- | Reexports <a>Data.Functor.Identity.Compat</a> from a globally unique
--   namespace.
module Data.Functor.Identity.Compat.Repl

module Data.Functor.Product.Compat


-- | Reexports <a>Data.Functor.Product.Compat</a> from a globally unique
--   namespace.
module Data.Functor.Product.Compat.Repl

module Data.Functor.Sum.Compat


-- | Reexports <a>Data.Functor.Sum.Compat</a> from a globally unique
--   namespace.
module Data.Functor.Sum.Compat.Repl

module Data.IORef.Compat

-- | Strict version of <a>modifyIORef</a>
modifyIORef' :: () => IORef a -> a -> a -> IO ()

-- | Strict version of <a>atomicModifyIORef</a>. This forces both the value
--   stored in the <a>IORef</a> as well as the value returned.
atomicModifyIORef' :: () => IORef a -> a -> (a, b) -> IO b

-- | Variant of <a>writeIORef</a> with the "barrier to reordering" property
--   that <a>atomicModifyIORef</a> has.
atomicWriteIORef :: () => IORef a -> a -> IO ()


-- | Reexports <a>Data.IORef.Compat</a> from a globally unique namespace.
module Data.IORef.Compat.Repl

module Data.List.Compat


-- | Reexports <a>Data.List.Compat</a> from a globally unique namespace.
module Data.List.Compat.Repl


-- | This backports the modern <a>Data.Semigroup</a> interface back to
--   <tt>base-4.9</tt>/GHC 8.0.
module Data.List.NonEmpty.Compat

-- | Non-empty (and non-strict) list type.
data NonEmpty a
(:|) :: a -> [a] -> NonEmpty a

-- | Map a function over a <a>NonEmpty</a> stream.
map :: () => a -> b -> NonEmpty a -> NonEmpty b

-- | 'intersperse x xs' alternates elements of the list with copies of
--   <tt>x</tt>.
--   
--   <pre>
--   intersperse 0 (1 :| [2,3]) == 1 :| [0,2,0,3]
--   </pre>
intersperse :: () => a -> NonEmpty a -> NonEmpty a

-- | <a>scanl</a> is similar to <a>foldl</a>, but returns a stream of
--   successive reduced values from the left:
--   
--   <pre>
--   scanl f z [x1, x2, ...] == z :| [z `f` x1, (z `f` x1) `f` x2, ...]
--   </pre>
--   
--   Note that
--   
--   <pre>
--   last (scanl f z xs) == foldl f z xs.
--   </pre>
scanl :: Foldable f => b -> a -> b -> b -> f a -> NonEmpty b

-- | <a>scanr</a> is the right-to-left dual of <a>scanl</a>. Note that
--   
--   <pre>
--   head (scanr f z xs) == foldr f z xs.
--   </pre>
scanr :: Foldable f => a -> b -> b -> b -> f a -> NonEmpty b

-- | <a>scanl1</a> is a variant of <a>scanl</a> that has no starting value
--   argument:
--   
--   <pre>
--   scanl1 f [x1, x2, ...] == x1 :| [x1 `f` x2, x1 `f` (x2 `f` x3), ...]
--   </pre>
scanl1 :: () => a -> a -> a -> NonEmpty a -> NonEmpty a

-- | <a>scanr1</a> is a variant of <a>scanr</a> that has no starting value
--   argument.
scanr1 :: () => a -> a -> a -> NonEmpty a -> NonEmpty a

-- | <a>transpose</a> for <a>NonEmpty</a>, behaves the same as
--   <a>transpose</a> The rows/columns need not be the same length, in
--   which case &gt; transpose . transpose /= id
transpose :: () => NonEmpty NonEmpty a -> NonEmpty NonEmpty a

-- | <a>sortBy</a> for <a>NonEmpty</a>, behaves the same as <a>sortBy</a>
sortBy :: () => a -> a -> Ordering -> NonEmpty a -> NonEmpty a

-- | <a>sortWith</a> for <a>NonEmpty</a>, behaves the same as:
--   
--   <pre>
--   sortBy . comparing
--   </pre>
sortWith :: Ord o => a -> o -> NonEmpty a -> NonEmpty a

-- | Number of elements in <a>NonEmpty</a> list.
length :: () => NonEmpty a -> Int

-- | Extract the first element of the stream.
head :: () => NonEmpty a -> a

-- | Extract the possibly-empty tail of the stream.
tail :: () => NonEmpty a -> [a]

-- | Extract the last element of the stream.
last :: () => NonEmpty a -> a

-- | Extract everything except the last element of the stream.
init :: () => NonEmpty a -> [a]

-- | Prepend an element to the stream.
(<|) :: () => a -> NonEmpty a -> NonEmpty a
infixr 5 <|

-- | Synonym for <a>&lt;|</a>.
cons :: () => a -> NonEmpty a -> NonEmpty a

-- | <a>uncons</a> produces the first element of the stream, and a stream
--   of the remaining elements, if any.
uncons :: () => NonEmpty a -> (a, Maybe NonEmpty a)

-- | The <a>unfoldr</a> function is analogous to <a>Data.List</a>'s
--   <a>unfoldr</a> operation.
unfoldr :: () => a -> (b, Maybe a) -> a -> NonEmpty b

-- | Sort a stream.
sort :: Ord a => NonEmpty a -> NonEmpty a

-- | <a>reverse</a> a finite NonEmpty stream.
reverse :: () => NonEmpty a -> NonEmpty a

-- | The <a>inits</a> function takes a stream <tt>xs</tt> and returns all
--   the finite prefixes of <tt>xs</tt>.
inits :: Foldable f => f a -> NonEmpty [a]

-- | The <a>tails</a> function takes a stream <tt>xs</tt> and returns all
--   the suffixes of <tt>xs</tt>.
tails :: Foldable f => f a -> NonEmpty [a]

-- | <tt><a>iterate</a> f x</tt> produces the infinite sequence of repeated
--   applications of <tt>f</tt> to <tt>x</tt>.
--   
--   <pre>
--   iterate f x = x :| [f x, f (f x), ..]
--   </pre>
iterate :: () => a -> a -> a -> NonEmpty a

-- | <tt><a>repeat</a> x</tt> returns a constant stream, where all elements
--   are equal to <tt>x</tt>.
repeat :: () => a -> NonEmpty a

-- | <tt><a>cycle</a> xs</tt> returns the infinite repetition of
--   <tt>xs</tt>:
--   
--   <pre>
--   cycle (1 :| [2,3]) = 1 :| [2,3,1,2,3,...]
--   </pre>
cycle :: () => NonEmpty a -> NonEmpty a

-- | <a>unfold</a> produces a new stream by repeatedly applying the
--   unfolding function to the seed value to produce an element of type
--   <tt>b</tt> and a new seed value. When the unfolding function returns
--   <a>Nothing</a> instead of a new seed value, the stream ends.
unfold :: () => a -> (b, Maybe a) -> a -> NonEmpty b

-- | <tt><a>insert</a> x xs</tt> inserts <tt>x</tt> into the last position
--   in <tt>xs</tt> where it is still less than or equal to the next
--   element. In particular, if the list is sorted beforehand, the result
--   will also be sorted.
insert :: (Foldable f, Ord a) => a -> f a -> NonEmpty a

-- | <tt><a>some1</a> x</tt> sequences <tt>x</tt> one or more times.
some1 :: Alternative f => f a -> f NonEmpty a

-- | <tt><a>take</a> n xs</tt> returns the first <tt>n</tt> elements of
--   <tt>xs</tt>.
take :: () => Int -> NonEmpty a -> [a]

-- | <tt><a>drop</a> n xs</tt> drops the first <tt>n</tt> elements off the
--   front of the sequence <tt>xs</tt>.
drop :: () => Int -> NonEmpty a -> [a]

-- | <tt><a>splitAt</a> n xs</tt> returns a pair consisting of the prefix
--   of <tt>xs</tt> of length <tt>n</tt> and the remaining stream
--   immediately following this prefix.
--   
--   <pre>
--   'splitAt' n xs == ('take' n xs, 'drop' n xs)
--   xs == ys ++ zs where (ys, zs) = 'splitAt' n xs
--   </pre>
splitAt :: () => Int -> NonEmpty a -> ([a], [a])

-- | <tt><a>takeWhile</a> p xs</tt> returns the longest prefix of the
--   stream <tt>xs</tt> for which the predicate <tt>p</tt> holds.
takeWhile :: () => a -> Bool -> NonEmpty a -> [a]

-- | <tt><a>dropWhile</a> p xs</tt> returns the suffix remaining after
--   <tt><a>takeWhile</a> p xs</tt>.
dropWhile :: () => a -> Bool -> NonEmpty a -> [a]

-- | <tt><a>span</a> p xs</tt> returns the longest prefix of <tt>xs</tt>
--   that satisfies <tt>p</tt>, together with the remainder of the stream.
--   
--   <pre>
--   'span' p xs == ('takeWhile' p xs, 'dropWhile' p xs)
--   xs == ys ++ zs where (ys, zs) = 'span' p xs
--   </pre>
span :: () => a -> Bool -> NonEmpty a -> ([a], [a])

-- | The <tt><a>break</a> p</tt> function is equivalent to <tt><a>span</a>
--   (not . p)</tt>.
break :: () => a -> Bool -> NonEmpty a -> ([a], [a])

-- | <tt><a>filter</a> p xs</tt> removes any elements from <tt>xs</tt> that
--   do not satisfy <tt>p</tt>.
filter :: () => a -> Bool -> NonEmpty a -> [a]

-- | The <a>partition</a> function takes a predicate <tt>p</tt> and a
--   stream <tt>xs</tt>, and returns a pair of lists. The first list
--   corresponds to the elements of <tt>xs</tt> for which <tt>p</tt> holds;
--   the second corresponds to the elements of <tt>xs</tt> for which
--   <tt>p</tt> does not hold.
--   
--   <pre>
--   'partition' p xs = ('filter' p xs, 'filter' (not . p) xs)
--   </pre>
partition :: () => a -> Bool -> NonEmpty a -> ([a], [a])

-- | The <a>group</a> function takes a stream and returns a list of streams
--   such that flattening the resulting list is equal to the argument.
--   Moreover, each stream in the resulting list contains only equal
--   elements. For example, in list notation:
--   
--   <pre>
--   'group' $ 'cycle' "Mississippi"
--     = "M" : "i" : "ss" : "i" : "ss" : "i" : "pp" : "i" : "M" : "i" : ...
--   </pre>
group :: (Foldable f, Eq a) => f a -> [NonEmpty a]

-- | <a>groupBy</a> operates like <a>group</a>, but uses the provided
--   equality predicate instead of <a>==</a>.
groupBy :: Foldable f => a -> a -> Bool -> f a -> [NonEmpty a]

-- | <a>groupWith</a> operates like <a>group</a>, but uses the provided
--   projection when comparing for equality
groupWith :: (Foldable f, Eq b) => a -> b -> f a -> [NonEmpty a]

-- | <a>groupAllWith</a> operates like <a>groupWith</a>, but sorts the list
--   first so that each equivalence class has, at most, one list in the
--   output
groupAllWith :: Ord b => a -> b -> [a] -> [NonEmpty a]

-- | <a>group1</a> operates like <a>group</a>, but uses the knowledge that
--   its input is non-empty to produce guaranteed non-empty output.
group1 :: Eq a => NonEmpty a -> NonEmpty NonEmpty a

-- | <a>groupBy1</a> is to <a>group1</a> as <a>groupBy</a> is to
--   <a>group</a>.
groupBy1 :: () => a -> a -> Bool -> NonEmpty a -> NonEmpty NonEmpty a

-- | <a>groupWith1</a> is to <a>group1</a> as <a>groupWith</a> is to
--   <a>group</a>
groupWith1 :: Eq b => a -> b -> NonEmpty a -> NonEmpty NonEmpty a

-- | <a>groupAllWith1</a> is to <a>groupWith1</a> as <a>groupAllWith</a> is
--   to <a>groupWith</a>
groupAllWith1 :: Ord b => a -> b -> NonEmpty a -> NonEmpty NonEmpty a

-- | The <tt>isPrefix</tt> function returns <tt>True</tt> if the first
--   argument is a prefix of the second.
isPrefixOf :: Eq a => [a] -> NonEmpty a -> Bool

-- | The <a>nub</a> function removes duplicate elements from a list. In
--   particular, it keeps only the first occurrence of each element. (The
--   name <a>nub</a> means 'essence'.) It is a special case of
--   <a>nubBy</a>, which allows the programmer to supply their own
--   inequality test.
nub :: Eq a => NonEmpty a -> NonEmpty a

-- | The <a>nubBy</a> function behaves just like <a>nub</a>, except it uses
--   a user-supplied equality predicate instead of the overloaded <a>==</a>
--   function.
nubBy :: () => a -> a -> Bool -> NonEmpty a -> NonEmpty a

-- | <tt>xs !! n</tt> returns the element of the stream <tt>xs</tt> at
--   index <tt>n</tt>. Note that the head of the stream has index 0.
--   
--   <i>Beware</i>: a negative or out-of-bounds index will cause an error.
(!!) :: () => NonEmpty a -> Int -> a
infixl 9 !!

-- | The <a>zip</a> function takes two streams and returns a stream of
--   corresponding pairs.
zip :: () => NonEmpty a -> NonEmpty b -> NonEmpty (a, b)

-- | The <a>zipWith</a> function generalizes <a>zip</a>. Rather than
--   tupling the elements, the elements are combined using the function
--   passed as the first argument.
zipWith :: () => a -> b -> c -> NonEmpty a -> NonEmpty b -> NonEmpty c

-- | The <a>unzip</a> function is the inverse of the <a>zip</a> function.
unzip :: Functor f => f (a, b) -> (f a, f b)

-- | Converts a normal list to a <a>NonEmpty</a> stream.
--   
--   Raises an error if given an empty list.
fromList :: () => [a] -> NonEmpty a

-- | Convert a stream to a normal list efficiently.
toList :: () => NonEmpty a -> [a]

-- | <a>nonEmpty</a> efficiently turns a normal list into a <a>NonEmpty</a>
--   stream, producing <a>Nothing</a> if the input is empty.
nonEmpty :: () => [a] -> Maybe NonEmpty a

-- | Compute n-ary logic exclusive OR operation on <a>NonEmpty</a> list.
xor :: NonEmpty Bool -> Bool


-- | Reexports <a>Data.List.NonEmpty.Compat</a> from a globally unique
--   namespace.
module Data.List.NonEmpty.Compat.Repl

module Data.Monoid.Compat

-- | The class of monoids (types with an associative binary operation that
--   has an identity). Instances should satisfy the following laws:
--   
--   <ul>
--   <li><pre>x <a>&lt;&gt;</a> <a>mempty</a> = x</pre></li>
--   <li><pre><a>mempty</a> <a>&lt;&gt;</a> x = x</pre></li>
--   <li><tt>x <a>&lt;&gt;</a> (y <a>&lt;&gt;</a> z) = (x <a>&lt;&gt;</a>
--   y) <a>&lt;&gt;</a> z</tt> (<a>Semigroup</a> law)</li>
--   <li><pre><a>mconcat</a> = <a>foldr</a> '(&lt;&gt;)'
--   <a>mempty</a></pre></li>
--   </ul>
--   
--   The method names refer to the monoid of lists under concatenation, but
--   there are many other instances.
--   
--   Some types can be viewed as a monoid in more than one way, e.g. both
--   addition and multiplication on numbers. In such cases we often define
--   <tt>newtype</tt>s and make those instances of <a>Monoid</a>, e.g.
--   <tt>Sum</tt> and <tt>Product</tt>.
--   
--   <b>NOTE</b>: <a>Semigroup</a> is a superclass of <a>Monoid</a> since
--   <i>base-4.11.0.0</i>.
class Semigroup a => Monoid a

-- | Identity of <a>mappend</a>
mempty :: Monoid a => a

-- | An associative operation
--   
--   <b>NOTE</b>: This method is redundant and has the default
--   implementation <tt><a>mappend</a> = '(&lt;&gt;)'</tt> since
--   <i>base-4.11.0.0</i>.
mappend :: Monoid a => a -> a -> a

-- | Fold a list using the monoid.
--   
--   For most types, the default definition for <a>mconcat</a> will be
--   used, but the function is included in the class definition so that an
--   optimized version can be provided for specific types.
mconcat :: Monoid a => [a] -> a

-- | Maybe monoid returning the leftmost non-Nothing value.
--   
--   <tt><a>First</a> a</tt> is isomorphic to <tt><a>Alt</a> <a>Maybe</a>
--   a</tt>, but precedes it historically.
--   
--   <pre>
--   &gt;&gt;&gt; getFirst (First (Just "hello") &lt;&gt; First Nothing &lt;&gt; First (Just "world"))
--   Just "hello"
--   </pre>
newtype First a
First :: Maybe a -> First a
[getFirst] :: First a -> Maybe a

-- | Maybe monoid returning the rightmost non-Nothing value.
--   
--   <tt><a>Last</a> a</tt> is isomorphic to <tt><a>Dual</a> (<a>First</a>
--   a)</tt>, and thus to <tt><a>Dual</a> (<a>Alt</a> <a>Maybe</a> a)</tt>
--   
--   <pre>
--   &gt;&gt;&gt; getLast (Last (Just "hello") &lt;&gt; Last Nothing &lt;&gt; Last (Just "world"))
--   Just "world"
--   </pre>
newtype Last a
Last :: Maybe a -> Last a
[getLast] :: Last a -> Maybe a

-- | The dual of a <a>Monoid</a>, obtained by swapping the arguments of
--   <a>mappend</a>.
--   
--   <pre>
--   &gt;&gt;&gt; getDual (mappend (Dual "Hello") (Dual "World"))
--   "WorldHello"
--   </pre>
newtype Dual a
Dual :: a -> Dual a
[getDual] :: Dual a -> a

-- | The monoid of endomorphisms under composition.
--   
--   <pre>
--   &gt;&gt;&gt; let computation = Endo ("Hello, " ++) &lt;&gt; Endo (++ "!")
--   
--   &gt;&gt;&gt; appEndo computation "Haskell"
--   "Hello, Haskell!"
--   </pre>
newtype Endo a
Endo :: a -> a -> Endo a
[appEndo] :: Endo a -> a -> a

-- | Boolean monoid under conjunction (<a>&amp;&amp;</a>).
--   
--   <pre>
--   &gt;&gt;&gt; getAll (All True &lt;&gt; mempty &lt;&gt; All False)
--   False
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; getAll (mconcat (map (\x -&gt; All (even x)) [2,4,6,7,8]))
--   False
--   </pre>
newtype All
All :: Bool -> All
[getAll] :: All -> Bool

-- | Boolean monoid under disjunction (<a>||</a>).
--   
--   <pre>
--   &gt;&gt;&gt; getAny (Any True &lt;&gt; mempty &lt;&gt; Any False)
--   True
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; getAny (mconcat (map (\x -&gt; Any (even x)) [2,4,6,7,8]))
--   True
--   </pre>
newtype Any
Any :: Bool -> Any
[getAny] :: Any -> Bool

-- | Monoid under addition.
--   
--   <pre>
--   &gt;&gt;&gt; getSum (Sum 1 &lt;&gt; Sum 2 &lt;&gt; mempty)
--   3
--   </pre>
newtype Sum a
Sum :: a -> Sum a
[getSum] :: Sum a -> a

-- | Monoid under multiplication.
--   
--   <pre>
--   &gt;&gt;&gt; getProduct (Product 3 &lt;&gt; Product 4 &lt;&gt; mempty)
--   12
--   </pre>
newtype Product a
Product :: a -> Product a
[getProduct] :: Product a -> a

-- | Monoid under <a>&lt;|&gt;</a>.
newtype Alt (f :: k -> *) (a :: k) :: forall k. () => k -> * -> k -> *
Alt :: f a -> Alt
[getAlt] :: Alt -> f a

-- | An associative operation.
(<>) :: Semigroup a => a -> a -> a
infixr 6 <>


-- | Reexports <a>Data.Monoid.Compat</a> from a globally unique namespace.
module Data.Monoid.Compat.Repl

module Data.Proxy.Compat

-- | <a>asProxyTypeOf</a> is a type-restricted version of <a>const</a>. It
--   is usually used as an infix operator, and its typing forces its first
--   argument (which is usually overloaded) to have the same type as the
--   tag of the second.
--   
--   <pre>
--   &gt;&gt;&gt; import Data.Word
--   
--   &gt;&gt;&gt; :type asProxyTypeOf 123 (Proxy :: Proxy Word8)
--   asProxyTypeOf 123 (Proxy :: Proxy Word8) :: Word8
--   </pre>
--   
--   Note the lower-case <tt>proxy</tt> in the definition. This allows any
--   type constructor with just one argument to be passed to the function,
--   for example we could also write
--   
--   <pre>
--   &gt;&gt;&gt; import Data.Word
--   
--   &gt;&gt;&gt; :type asProxyTypeOf 123 (Just (undefined :: Word8))
--   asProxyTypeOf 123 (Just (undefined :: Word8)) :: Word8
--   </pre>
asProxyTypeOf :: () => a -> proxy a -> a


-- | Reexports <a>Data.Proxy.Compat</a> from a globally unique namespace.
module Data.Proxy.Compat.Repl

module Data.Ratio.Compat


-- | Reexports <a>Data.Ratio.Compat</a> from a globally unique namespace.
module Data.Ratio.Compat.Repl

module Data.STRef.Compat

-- | Strict version of <a>modifySTRef</a>
modifySTRef' :: () => STRef s a -> a -> a -> ST s ()


-- | Reexports <a>Data.STRef.Compat</a> from a globally unique namespace.
module Data.STRef.Compat.Repl


-- | This backports the modern <a>Data.Semigroup</a> interface back to
--   <tt>base-4.9</tt>/GHC 8.0.
module Data.Semigroup.Compat

-- | The class of semigroups (types with an associative binary operation).
--   
--   Instances should satisfy the associativity law:
--   
--   <ul>
--   <li><pre>x <a>&lt;&gt;</a> (y <a>&lt;&gt;</a> z) = (x <a>&lt;&gt;</a>
--   y) <a>&lt;&gt;</a> z</pre></li>
--   </ul>
class Semigroup a

-- | An associative operation.
(<>) :: Semigroup a => a -> a -> a

-- | Reduce a non-empty list with <tt>&lt;&gt;</tt>
--   
--   The default definition should be sufficient, but this can be
--   overridden for efficiency.
sconcat :: Semigroup a => NonEmpty a -> a

-- | Repeat a value <tt>n</tt> times.
--   
--   Given that this works on a <a>Semigroup</a> it is allowed to fail if
--   you request 0 or fewer repetitions, and the default definition will do
--   so.
--   
--   By making this a member of the class, idempotent semigroups and
--   monoids can upgrade this to execute in <i>O(1)</i> by picking
--   <tt>stimes = <tt>stimesIdempotent</tt></tt> or <tt>stimes =
--   <a>stimesIdempotentMonoid</a></tt> respectively.
stimes :: (Semigroup a, Integral b) => b -> a -> a

-- | This is a valid definition of <a>stimes</a> for a <a>Monoid</a>.
--   
--   Unlike the default definition of <a>stimes</a>, it is defined for 0
--   and so it should be preferred where possible.
stimesMonoid :: (Integral b, Monoid a) => b -> a -> a

-- | This is a valid definition of <a>stimes</a> for an idempotent
--   <a>Semigroup</a>.
--   
--   When <tt>x &lt;&gt; x = x</tt>, this definition should be preferred,
--   because it works in <i>O(1)</i> rather than <i>O(log n)</i>.
stimesIdempotent :: Integral b => b -> a -> a

-- | This is a valid definition of <a>stimes</a> for an idempotent
--   <a>Monoid</a>.
--   
--   When <tt>mappend x x = x</tt>, this definition should be preferred,
--   because it works in <i>O(1)</i> rather than <i>O(log n)</i>
stimesIdempotentMonoid :: (Integral b, Monoid a) => b -> a -> a

-- | Repeat a value <tt>n</tt> times.
--   
--   <pre>
--   mtimesDefault n a = a &lt;&gt; a &lt;&gt; ... &lt;&gt; a  -- using &lt;&gt; (n-1) times
--   </pre>
--   
--   Implemented using <a>stimes</a> and <a>mempty</a>.
--   
--   This is a suitable definition for an <tt>mtimes</tt> member of
--   <a>Monoid</a>.
mtimesDefault :: (Integral b, Monoid a) => b -> a -> a
newtype Min a
Min :: a -> Min a
[getMin] :: Min a -> a
newtype Max a
Max :: a -> Max a
[getMax] :: Max a -> a

-- | Use <tt><a>Option</a> (<a>First</a> a)</tt> to get the behavior of
--   <a>First</a> from <a>Data.Monoid</a>.
newtype First a
First :: a -> First a
[getFirst] :: First a -> a

-- | Use <tt><a>Option</a> (<a>Last</a> a)</tt> to get the behavior of
--   <a>Last</a> from <a>Data.Monoid</a>
newtype Last a
Last :: a -> Last a
[getLast] :: Last a -> a

-- | Provide a Semigroup for an arbitrary Monoid.
--   
--   <b>NOTE</b>: This is not needed anymore since <a>Semigroup</a> became
--   a superclass of <a>Monoid</a> in <i>base-4.11</i> and this newtype be
--   deprecated at some point in the future.
newtype WrappedMonoid m
WrapMonoid :: m -> WrappedMonoid m
[unwrapMonoid] :: WrappedMonoid m -> m

-- | The dual of a <a>Monoid</a>, obtained by swapping the arguments of
--   <a>mappend</a>.
--   
--   <pre>
--   &gt;&gt;&gt; getDual (mappend (Dual "Hello") (Dual "World"))
--   "WorldHello"
--   </pre>
newtype Dual a
Dual :: a -> Dual a
[getDual] :: Dual a -> a

-- | The monoid of endomorphisms under composition.
--   
--   <pre>
--   &gt;&gt;&gt; let computation = Endo ("Hello, " ++) &lt;&gt; Endo (++ "!")
--   
--   &gt;&gt;&gt; appEndo computation "Haskell"
--   "Hello, Haskell!"
--   </pre>
newtype Endo a
Endo :: a -> a -> Endo a
[appEndo] :: Endo a -> a -> a

-- | Boolean monoid under conjunction (<a>&amp;&amp;</a>).
--   
--   <pre>
--   &gt;&gt;&gt; getAll (All True &lt;&gt; mempty &lt;&gt; All False)
--   False
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; getAll (mconcat (map (\x -&gt; All (even x)) [2,4,6,7,8]))
--   False
--   </pre>
newtype All
All :: Bool -> All
[getAll] :: All -> Bool

-- | Boolean monoid under disjunction (<a>||</a>).
--   
--   <pre>
--   &gt;&gt;&gt; getAny (Any True &lt;&gt; mempty &lt;&gt; Any False)
--   True
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; getAny (mconcat (map (\x -&gt; Any (even x)) [2,4,6,7,8]))
--   True
--   </pre>
newtype Any
Any :: Bool -> Any
[getAny] :: Any -> Bool

-- | Monoid under addition.
--   
--   <pre>
--   &gt;&gt;&gt; getSum (Sum 1 &lt;&gt; Sum 2 &lt;&gt; mempty)
--   3
--   </pre>
newtype Sum a
Sum :: a -> Sum a
[getSum] :: Sum a -> a

-- | Monoid under multiplication.
--   
--   <pre>
--   &gt;&gt;&gt; getProduct (Product 3 &lt;&gt; Product 4 &lt;&gt; mempty)
--   12
--   </pre>
newtype Product a
Product :: a -> Product a
[getProduct] :: Product a -> a

-- | <a>Option</a> is effectively <a>Maybe</a> with a better instance of
--   <a>Monoid</a>, built off of an underlying <a>Semigroup</a> instead of
--   an underlying <a>Monoid</a>.
--   
--   Ideally, this type would not exist at all and we would just fix the
--   <a>Monoid</a> instance of <a>Maybe</a>
newtype Option a
Option :: Maybe a -> Option a
[getOption] :: Option a -> Maybe a

-- | Fold an <a>Option</a> case-wise, just like <a>maybe</a>.
option :: () => b -> a -> b -> Option a -> b

-- | This lets you use a difference list of a <a>Semigroup</a> as a
--   <a>Monoid</a>.
diff :: Semigroup m => m -> Endo m

-- | A generalization of <a>cycle</a> to an arbitrary <a>Semigroup</a>. May
--   fail to terminate for some values in some semigroups.
cycle1 :: Semigroup m => m -> m

-- | <a>Arg</a> isn't itself a <a>Semigroup</a> in its own right, but it
--   can be placed inside <a>Min</a> and <a>Max</a> to compute an arg min
--   or arg max.
data Arg a b
Arg :: a -> b -> Arg a b
type ArgMin a b = Min Arg a b
type ArgMax a b = Max Arg a b


-- | Reexports <a>Data.Semigroup.Compat</a> from a globally unique
--   namespace.
module Data.Semigroup.Compat.Repl

module Data.String.Compat

-- | A <a>String</a> is a list of characters. String constants in Haskell
--   are values of type <a>String</a>.
type String = [Char]

-- | <a>lines</a> breaks a string up into a list of strings at newline
--   characters. The resulting strings do not contain newlines.
--   
--   Note that after splitting the string at newline characters, the last
--   part of the string is considered a line even if it doesn't end with a
--   newline. For example,
--   
--   <pre>
--   &gt;&gt;&gt; lines ""
--   []
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "\n"
--   [""]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "one"
--   ["one"]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "one\n"
--   ["one"]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "one\n\n"
--   ["one",""]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "one\ntwo"
--   ["one","two"]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "one\ntwo\n"
--   ["one","two"]
--   </pre>
--   
--   Thus <tt><a>lines</a> s</tt> contains at least as many elements as
--   newlines in <tt>s</tt>.
lines :: String -> [String]

-- | <a>words</a> breaks a string up into a list of words, which were
--   delimited by white space.
--   
--   <pre>
--   &gt;&gt;&gt; words "Lorem ipsum\ndolor"
--   ["Lorem","ipsum","dolor"]
--   </pre>
words :: String -> [String]

-- | <a>unlines</a> is an inverse operation to <a>lines</a>. It joins
--   lines, after appending a terminating newline to each.
--   
--   <pre>
--   &gt;&gt;&gt; unlines ["Hello", "World", "!"]
--   "Hello\nWorld\n!\n"
--   </pre>
unlines :: [String] -> String

-- | <a>unwords</a> is an inverse operation to <a>words</a>. It joins words
--   with separating spaces.
--   
--   <pre>
--   &gt;&gt;&gt; unwords ["Lorem", "ipsum", "dolor"]
--   "Lorem ipsum dolor"
--   </pre>
unwords :: [String] -> String


-- | Reexports <a>Data.String.Compat</a> from a globally unique namespace.
module Data.String.Compat.Repl

module Data.Type.Coercion.Compat

-- | Generalized form of type-safe cast using representational equality
gcoerceWith :: () => Coercion a b -> Coercible a b -> r -> r


-- | Reexports <a>Data.Type.Coercion.Compat</a> from a globally unique
--   namespace.
module Data.Type.Coercion.Compat.Repl

module Data.Version.Compat

-- | Construct tag-less <a>Version</a>
makeVersion :: [Int] -> Version


-- | Reexports <a>Data.Version.Compat</a> from a globally unique namespace.
module Data.Version.Compat.Repl

module Data.Void.Compat


-- | Reexports <a>Data.Void.Compat</a> from a globally unique namespace.
module Data.Void.Compat.Repl

module Data.Word.Compat

-- | Swap bytes in <a>Word16</a>.
byteSwap16 :: Word16 -> Word16

-- | Reverse order of bytes in <a>Word32</a>.
byteSwap32 :: Word32 -> Word32

-- | Reverse order of bytes in <a>Word64</a>.
byteSwap64 :: Word64 -> Word64


-- | Reexports <a>Data.Word.Compat</a> from a globally unique namespace.
module Data.Word.Compat.Repl

module Debug.Trace.Compat

-- | Like <a>trace</a> but returns the message instead of a third value.
--   
--   <pre>
--   &gt;&gt;&gt; traceId "hello"
--   "hello
--   hello"
--   </pre>
traceId :: String -> String

-- | Like <a>traceShow</a> but returns the shown value instead of a third
--   value.
--   
--   <pre>
--   &gt;&gt;&gt; traceShowId (1+2+3, "hello" ++ "world")
--   (6,"helloworld")
--   (6,"helloworld")
--   </pre>
traceShowId :: Show a => a -> a

-- | Like <a>trace</a> but returning unit in an arbitrary
--   <a>Applicative</a> context. Allows for convenient use in do-notation.
--   
--   Note that the application of <a>traceM</a> is not an action in the
--   <a>Applicative</a> context, as <a>traceIO</a> is in the <a>IO</a>
--   type. While the fresh bindings in the following example will force the
--   <a>traceM</a> expressions to be reduced every time the
--   <tt>do</tt>-block is executed, <tt>traceM "not crashed"</tt> would
--   only be reduced once, and the message would only be printed once. If
--   your monad is in <tt>MonadIO</tt>, <tt>liftIO . traceIO</tt> may be a
--   better option.
--   
--   <pre>
--   &gt;&gt;&gt; :{
--   do
--       x &lt;- Just 3
--       traceM ("x: " ++ show x)
--       y &lt;- pure 12
--       traceM ("y: " ++ show y)
--       pure (x*2 + y)
--   :}
--   x: 3
--   y: 12
--   Just 18
--   </pre>
traceM :: Applicative f => String -> f ()

-- | Like <a>traceM</a>, but uses <a>show</a> on the argument to convert it
--   to a <a>String</a>.
--   
--   <pre>
--   &gt;&gt;&gt; :{
--   do
--       x &lt;- Just 3
--       traceShowM x
--       y &lt;- pure 12
--       traceShowM y
--       pure (x*2 + y)
--   :}
--   3
--   12
--   Just 18
--   </pre>
traceShowM :: (Show a, Applicative f) => a -> f ()


-- | Reexports <a>Debug.Trace.Compat</a> from a globally unique namespace.
module Debug.Trace.Compat.Repl

module Foreign.ForeignPtr.Compat

-- | Advances the given address by the given offset in bytes.
--   
--   The new <a>ForeignPtr</a> shares the finalizer of the original,
--   equivalent from a finalization standpoint to just creating another
--   reference to the original. That is, the finalizer will not be called
--   before the new <a>ForeignPtr</a> is unreachable, nor will it be called
--   an additional time due to this call, and the finalizer will be called
--   with the same address that it would have had this call not happened,
--   *not* the new address.
plusForeignPtr :: () => ForeignPtr a -> Int -> ForeignPtr b


-- | Reexports <a>Foreign.ForeignPtr.Compat</a> from a globally unique
--   namespace.
module Foreign.ForeignPtr.Compat.Repl

module Foreign.ForeignPtr.Safe.Compat

-- | The type <a>ForeignPtr</a> represents references to objects that are
--   maintained in a foreign language, i.e., that are not part of the data
--   structures usually managed by the Haskell storage manager. The
--   essential difference between <a>ForeignPtr</a>s and vanilla memory
--   references of type <tt>Ptr a</tt> is that the former may be associated
--   with <i>finalizers</i>. A finalizer is a routine that is invoked when
--   the Haskell storage manager detects that - within the Haskell heap and
--   stack - there are no more references left that are pointing to the
--   <a>ForeignPtr</a>. Typically, the finalizer will, then, invoke
--   routines in the foreign language that free the resources bound by the
--   foreign object.
--   
--   The <a>ForeignPtr</a> is parameterised in the same way as <a>Ptr</a>.
--   The type argument of <a>ForeignPtr</a> should normally be an instance
--   of class <a>Storable</a>.
data ForeignPtr a

-- | A finalizer is represented as a pointer to a foreign function that, at
--   finalisation time, gets as an argument a plain pointer variant of the
--   foreign pointer that the finalizer is associated with.
--   
--   Note that the foreign function <i>must</i> use the <tt>ccall</tt>
--   calling convention.
type FinalizerPtr a = FunPtr Ptr a -> IO ()
type FinalizerEnvPtr env a = FunPtr Ptr env -> Ptr a -> IO ()

-- | Turns a plain memory reference into a foreign pointer, and associates
--   a finalizer with the reference. The finalizer will be executed after
--   the last reference to the foreign object is dropped. There is no
--   guarantee of promptness, however the finalizer will be executed before
--   the program exits.
newForeignPtr :: () => FinalizerPtr a -> Ptr a -> IO ForeignPtr a

-- | Turns a plain memory reference into a foreign pointer that may be
--   associated with finalizers by using <a>addForeignPtrFinalizer</a>.
newForeignPtr_ :: () => Ptr a -> IO ForeignPtr a

-- | This function adds a finalizer to the given foreign object. The
--   finalizer will run <i>before</i> all other finalizers for the same
--   object which have already been registered.
addForeignPtrFinalizer :: () => FinalizerPtr a -> ForeignPtr a -> IO ()

-- | This variant of <a>newForeignPtr</a> adds a finalizer that expects an
--   environment in addition to the finalized pointer. The environment that
--   will be passed to the finalizer is fixed by the second argument to
--   <a>newForeignPtrEnv</a>.
newForeignPtrEnv :: () => FinalizerEnvPtr env a -> Ptr env -> Ptr a -> IO ForeignPtr a

-- | Like <a>addForeignPtrFinalizerEnv</a> but allows the finalizer to be
--   passed an additional environment parameter to be passed to the
--   finalizer. The environment passed to the finalizer is fixed by the
--   second argument to <a>addForeignPtrFinalizerEnv</a>
addForeignPtrFinalizerEnv :: () => FinalizerEnvPtr env a -> Ptr env -> ForeignPtr a -> IO ()

-- | This is a way to look at the pointer living inside a foreign object.
--   This function takes a function which is applied to that pointer. The
--   resulting <a>IO</a> action is then executed. The foreign object is
--   kept alive at least during the whole action, even if it is not used
--   directly inside. Note that it is not safe to return the pointer from
--   the action and use it after the action completes. All uses of the
--   pointer should be inside the <a>withForeignPtr</a> bracket. The reason
--   for this unsafeness is the same as for <a>unsafeForeignPtrToPtr</a>
--   below: the finalizer may run earlier than expected, because the
--   compiler can only track usage of the <a>ForeignPtr</a> object, not a
--   <a>Ptr</a> object made from it.
--   
--   This function is normally used for marshalling data to or from the
--   object pointed to by the <a>ForeignPtr</a>, using the operations from
--   the <a>Storable</a> class.
withForeignPtr :: () => ForeignPtr a -> Ptr a -> IO b -> IO b

-- | Causes the finalizers associated with a foreign pointer to be run
--   immediately.
finalizeForeignPtr :: () => ForeignPtr a -> IO ()

-- | This function ensures that the foreign object in question is alive at
--   the given place in the sequence of IO actions. In particular
--   <a>withForeignPtr</a> does a <a>touchForeignPtr</a> after it executes
--   the user action.
--   
--   Note that this function should not be used to express dependencies
--   between finalizers on <a>ForeignPtr</a>s. For example, if the
--   finalizer for a <a>ForeignPtr</a> <tt>F1</tt> calls
--   <a>touchForeignPtr</a> on a second <a>ForeignPtr</a> <tt>F2</tt>, then
--   the only guarantee is that the finalizer for <tt>F2</tt> is never
--   started before the finalizer for <tt>F1</tt>. They might be started
--   together if for example both <tt>F1</tt> and <tt>F2</tt> are otherwise
--   unreachable, and in that case the scheduler might end up running the
--   finalizer for <tt>F2</tt> first.
--   
--   In general, it is not recommended to use finalizers on separate
--   objects with ordering constraints between them. To express the
--   ordering robustly requires explicit synchronisation using
--   <tt>MVar</tt>s between the finalizers, but even then the runtime
--   sometimes runs multiple finalizers sequentially in a single thread
--   (for performance reasons), so synchronisation between finalizers could
--   result in artificial deadlock. Another alternative is to use explicit
--   reference counting.
touchForeignPtr :: () => ForeignPtr a -> IO ()

-- | This function casts a <a>ForeignPtr</a> parameterised by one type into
--   another type.
castForeignPtr :: () => ForeignPtr a -> ForeignPtr b

-- | Allocate some memory and return a <a>ForeignPtr</a> to it. The memory
--   will be released automatically when the <a>ForeignPtr</a> is
--   discarded.
--   
--   <a>mallocForeignPtr</a> is equivalent to
--   
--   <pre>
--   do { p &lt;- malloc; newForeignPtr finalizerFree p }
--   </pre>
--   
--   although it may be implemented differently internally: you may not
--   assume that the memory returned by <a>mallocForeignPtr</a> has been
--   allocated with <a>malloc</a>.
--   
--   GHC notes: <a>mallocForeignPtr</a> has a heavily optimised
--   implementation in GHC. It uses pinned memory in the garbage collected
--   heap, so the <a>ForeignPtr</a> does not require a finalizer to free
--   the memory. Use of <a>mallocForeignPtr</a> and associated functions is
--   strongly recommended in preference to <tt>newForeignPtr</tt> with a
--   finalizer.
mallocForeignPtr :: Storable a => IO ForeignPtr a

-- | This function is similar to <a>mallocForeignPtr</a>, except that the
--   size of the memory required is given explicitly as a number of bytes.
mallocForeignPtrBytes :: () => Int -> IO ForeignPtr a

-- | This function is similar to <a>mallocArray</a>, but yields a memory
--   area that has a finalizer attached that releases the memory area. As
--   with <a>mallocForeignPtr</a>, it is not guaranteed that the block of
--   memory was allocated by <a>malloc</a>.
mallocForeignPtrArray :: Storable a => Int -> IO ForeignPtr a

-- | This function is similar to <a>mallocArray0</a>, but yields a memory
--   area that has a finalizer attached that releases the memory area. As
--   with <a>mallocForeignPtr</a>, it is not guaranteed that the block of
--   memory was allocated by <a>malloc</a>.
mallocForeignPtrArray0 :: Storable a => Int -> IO ForeignPtr a


-- | Reexports <a>Foreign.ForeignPtr.Safe.Compat</a> from a globally unique
--   namespace.
module Foreign.ForeignPtr.Safe.Compat.Repl

module Foreign.ForeignPtr.Unsafe.Compat

-- | This function extracts the pointer component of a foreign pointer.
--   This is a potentially dangerous operations, as if the argument to
--   <a>unsafeForeignPtrToPtr</a> is the last usage occurrence of the given
--   foreign pointer, then its finalizer(s) will be run, which potentially
--   invalidates the plain pointer just obtained. Hence,
--   <a>touchForeignPtr</a> must be used wherever it has to be guaranteed
--   that the pointer lives on - i.e., has another usage occurrence.
--   
--   To avoid subtle coding errors, hand written marshalling code should
--   preferably use <a>withForeignPtr</a> rather than combinations of
--   <a>unsafeForeignPtrToPtr</a> and <a>touchForeignPtr</a>. However, the
--   latter routines are occasionally preferred in tool generated
--   marshalling code.
unsafeForeignPtrToPtr :: () => ForeignPtr a -> Ptr a


-- | Reexports <a>Foreign.ForeignPtr.Unsafe.Compat</a> from a globally
--   unique namespace.
module Foreign.ForeignPtr.Unsafe.Compat.Repl

module Foreign.Marshal.Alloc.Compat

-- | Like <a>malloc</a> but memory is filled with bytes of value zero.
calloc :: Storable a => IO Ptr a

-- | Llike <a>mallocBytes</a> but memory is filled with bytes of value
--   zero.
callocBytes :: () => Int -> IO Ptr a


-- | Reexports <a>Foreign.Marshal.Alloc.Compat</a> from a globally unique
--   namespace.
module Foreign.Marshal.Alloc.Compat.Repl

module Foreign.Marshal.Array.Compat

-- | Like <a>mallocArray</a>, but allocated memory is filled with bytes of
--   value zero.
callocArray :: Storable a => Int -> IO Ptr a

-- | Like <a>callocArray0</a>, but allocated memory is filled with bytes of
--   value zero.
callocArray0 :: Storable a => Int -> IO Ptr a


-- | Reexports <a>Foreign.Marshal.Array.Compat</a> from a globally unique
--   namespace.
module Foreign.Marshal.Array.Compat.Repl

module Foreign.Marshal.Safe.Compat


-- | Reexports <a>Foreign.Marshal.Safe.Compat</a> from a globally unique
--   namespace.
module Foreign.Marshal.Safe.Compat.Repl

module Foreign.Marshal.Unsafe.Compat

-- | Sometimes an external entity is a pure function, except that it passes
--   arguments and/or results via pointers. The function
--   <tt>unsafeLocalState</tt> permits the packaging of such entities as
--   pure functions.
--   
--   The only IO operations allowed in the IO action passed to
--   <tt>unsafeLocalState</tt> are (a) local allocation (<tt>alloca</tt>,
--   <tt>allocaBytes</tt> and derived operations such as <tt>withArray</tt>
--   and <tt>withCString</tt>), and (b) pointer operations
--   (<tt>Foreign.Storable</tt> and <tt>Foreign.Ptr</tt>) on the pointers
--   to local storage, and (c) foreign functions whose only observable
--   effect is to read and/or write the locally allocated memory. Passing
--   an IO operation that does not obey these rules results in undefined
--   behaviour.
--   
--   It is expected that this operation will be replaced in a future
--   revision of Haskell.
unsafeLocalState :: () => IO a -> a


-- | Reexports <a>Foreign.Marshal.Unsafe.Compat</a> from a globally unique
--   namespace.
module Foreign.Marshal.Unsafe.Compat.Repl

module Foreign.Marshal.Utils.Compat

-- | Fill a given number of bytes in memory area with a byte value.
fillBytes :: () => Ptr a -> Word8 -> Int -> IO ()

module Foreign.Marshal.Compat


-- | Reexports <a>Foreign.Marshal.Compat</a> from a globally unique
--   namespace.
module Foreign.Marshal.Compat.Repl

module Foreign.Compat


-- | Reexports <a>Foreign.Compat</a> from a globally unique namespace.
module Foreign.Compat.Repl


-- | Reexports <a>Foreign.Marshal.Utils.Compat</a> from a globally unique
--   namespace.
module Foreign.Marshal.Utils.Compat.Repl

module Numeric.Compat

-- | Show a signed <a>RealFloat</a> value using standard decimal notation
--   (e.g. <tt>245000</tt>, <tt>0.0015</tt>).
--   
--   This behaves as <a>showFFloat</a>, except that a decimal point is
--   always guaranteed, even if not needed.
showFFloatAlt :: RealFloat a => Maybe Int -> a -> ShowS

-- | Show a signed <a>RealFloat</a> value using standard decimal notation
--   for arguments whose absolute value lies between <tt>0.1</tt> and
--   <tt>9,999,999</tt>, and scientific notation otherwise.
--   
--   This behaves as <a>showFFloat</a>, except that a decimal point is
--   always guaranteed, even if not needed.
showGFloatAlt :: RealFloat a => Maybe Int -> a -> ShowS

-- | Show a floating-point value in the hexadecimal format, similar to the
--   <tt>%a</tt> specifier in C's printf.
--   
--   <pre>
--   &gt;&gt;&gt; showHFloat (212.21 :: Double) ""
--   "0x1.a86b851eb851fp7"
--   
--   &gt;&gt;&gt; showHFloat (-12.76 :: Float) ""
--   "-0x1.9851ecp3"
--   
--   &gt;&gt;&gt; showHFloat (-0 :: Double) ""
--   "-0x0p+0"
--   </pre>
showHFloat :: RealFloat a => a -> ShowS


-- | Reexports <a>Numeric.Compat</a> from a globally unique namespace.
module Numeric.Compat.Repl

module Numeric.Natural.Compat


-- | Reexports <a>Numeric.Natural.Compat</a> from a globally unique
--   namespace.
module Numeric.Natural.Compat.Repl

module Prelude.Compat

-- | Case analysis for the <a>Either</a> type. If the value is
--   <tt><a>Left</a> a</tt>, apply the first function to <tt>a</tt>; if it
--   is <tt><a>Right</a> b</tt>, apply the second function to <tt>b</tt>.
--   
--   <h4><b>Examples</b></h4>
--   
--   We create two values of type <tt><a>Either</a> <a>String</a>
--   <a>Int</a></tt>, one using the <a>Left</a> constructor and another
--   using the <a>Right</a> constructor. Then we apply "either" the
--   <tt>length</tt> function (if we have a <a>String</a>) or the
--   "times-two" function (if we have an <a>Int</a>):
--   
--   <pre>
--   &gt;&gt;&gt; let s = Left "foo" :: Either String Int
--   
--   &gt;&gt;&gt; let n = Right 3 :: Either String Int
--   
--   &gt;&gt;&gt; either length (*2) s
--   3
--   
--   &gt;&gt;&gt; either length (*2) n
--   6
--   </pre>
either :: () => a -> c -> b -> c -> Either a b -> c

-- | Determines whether all elements of the structure satisfy the
--   predicate.
all :: Foldable t => a -> Bool -> t a -> Bool

-- | <a>and</a> returns the conjunction of a container of Bools. For the
--   result to be <a>True</a>, the container must be finite; <a>False</a>,
--   however, results from a <a>False</a> value finitely far from the left
--   end.
and :: Foldable t => t Bool -> Bool

-- | Determines whether any element of the structure satisfies the
--   predicate.
any :: Foldable t => a -> Bool -> t a -> Bool

-- | The concatenation of all the elements of a container of lists.
concat :: Foldable t => t [a] -> [a]

-- | Map a function over all the elements of a container and concatenate
--   the resulting lists.
concatMap :: Foldable t => a -> [b] -> t a -> [b]

-- | Map each element of a structure to a monadic action, evaluate these
--   actions from left to right, and ignore the results. For a version that
--   doesn't ignore the results see <a>mapM</a>.
--   
--   As of base 4.8.0.0, <a>mapM_</a> is just <a>traverse_</a>, specialized
--   to <a>Monad</a>.
mapM_ :: (Foldable t, Monad m) => a -> m b -> t a -> m ()

-- | <a>notElem</a> is the negation of <a>elem</a>.
notElem :: (Foldable t, Eq a) => a -> t a -> Bool
infix 4 `notElem`

-- | <a>or</a> returns the disjunction of a container of Bools. For the
--   result to be <a>False</a>, the container must be finite; <a>True</a>,
--   however, results from a <a>True</a> value finitely far from the left
--   end.
or :: Foldable t => t Bool -> Bool

-- | Evaluate each monadic action in the structure from left to right, and
--   ignore the results. For a version that doesn't ignore the results see
--   <a>sequence</a>.
--   
--   As of base 4.8.0.0, <a>sequence_</a> is just <a>sequenceA_</a>,
--   specialized to <a>Monad</a>.
sequence_ :: (Foldable t, Monad m) => t m a -> m ()

-- | An infix synonym for <a>fmap</a>.
--   
--   The name of this operator is an allusion to <tt>$</tt>. Note the
--   similarities between their types:
--   
--   <pre>
--    ($)  ::              (a -&gt; b) -&gt;   a -&gt;   b
--   (&lt;$&gt;) :: Functor f =&gt; (a -&gt; b) -&gt; f a -&gt; f b
--   </pre>
--   
--   Whereas <tt>$</tt> is function application, <a>&lt;$&gt;</a> is
--   function application lifted over a <a>Functor</a>.
--   
--   <h4><b>Examples</b></h4>
--   
--   Convert from a <tt><tt>Maybe</tt> <tt>Int</tt></tt> to a
--   <tt><tt>Maybe</tt> <tt>String</tt></tt> using <tt>show</tt>:
--   
--   <pre>
--   &gt;&gt;&gt; show &lt;$&gt; Nothing
--   Nothing
--   
--   &gt;&gt;&gt; show &lt;$&gt; Just 3
--   Just "3"
--   </pre>
--   
--   Convert from an <tt><tt>Either</tt> <tt>Int</tt> <tt>Int</tt></tt> to
--   an <tt><tt>Either</tt> <tt>Int</tt></tt> <tt>String</tt> using
--   <tt>show</tt>:
--   
--   <pre>
--   &gt;&gt;&gt; show &lt;$&gt; Left 17
--   Left 17
--   
--   &gt;&gt;&gt; show &lt;$&gt; Right 17
--   Right "17"
--   </pre>
--   
--   Double each element of a list:
--   
--   <pre>
--   &gt;&gt;&gt; (*2) &lt;$&gt; [1,2,3]
--   [2,4,6]
--   </pre>
--   
--   Apply <tt>even</tt> to the second element of a pair:
--   
--   <pre>
--   &gt;&gt;&gt; even &lt;$&gt; (2,2)
--   (2,True)
--   </pre>
(<$>) :: Functor f => a -> b -> f a -> f b
infixl 4 <$>

-- | The <a>maybe</a> function takes a default value, a function, and a
--   <a>Maybe</a> value. If the <a>Maybe</a> value is <a>Nothing</a>, the
--   function returns the default value. Otherwise, it applies the function
--   to the value inside the <a>Just</a> and returns the result.
--   
--   <h4><b>Examples</b></h4>
--   
--   Basic usage:
--   
--   <pre>
--   &gt;&gt;&gt; maybe False odd (Just 3)
--   True
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; maybe False odd Nothing
--   False
--   </pre>
--   
--   Read an integer from a string using <tt>readMaybe</tt>. If we succeed,
--   return twice the integer; that is, apply <tt>(*2)</tt> to it. If
--   instead we fail to parse an integer, return <tt>0</tt> by default:
--   
--   <pre>
--   &gt;&gt;&gt; import Text.Read ( readMaybe )
--   
--   &gt;&gt;&gt; maybe 0 (*2) (readMaybe "5")
--   10
--   
--   &gt;&gt;&gt; maybe 0 (*2) (readMaybe "")
--   0
--   </pre>
--   
--   Apply <tt>show</tt> to a <tt>Maybe Int</tt>. If we have <tt>Just
--   n</tt>, we want to show the underlying <a>Int</a> <tt>n</tt>. But if
--   we have <a>Nothing</a>, we return the empty string instead of (for
--   example) "Nothing":
--   
--   <pre>
--   &gt;&gt;&gt; maybe "" show (Just 5)
--   "5"
--   
--   &gt;&gt;&gt; maybe "" show Nothing
--   ""
--   </pre>
maybe :: () => b -> a -> b -> Maybe a -> b

-- | <a>lines</a> breaks a string up into a list of strings at newline
--   characters. The resulting strings do not contain newlines.
--   
--   Note that after splitting the string at newline characters, the last
--   part of the string is considered a line even if it doesn't end with a
--   newline. For example,
--   
--   <pre>
--   &gt;&gt;&gt; lines ""
--   []
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "\n"
--   [""]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "one"
--   ["one"]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "one\n"
--   ["one"]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "one\n\n"
--   ["one",""]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "one\ntwo"
--   ["one","two"]
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; lines "one\ntwo\n"
--   ["one","two"]
--   </pre>
--   
--   Thus <tt><a>lines</a> s</tt> contains at least as many elements as
--   newlines in <tt>s</tt>.
lines :: String -> [String]

-- | <a>unlines</a> is an inverse operation to <a>lines</a>. It joins
--   lines, after appending a terminating newline to each.
--   
--   <pre>
--   &gt;&gt;&gt; unlines ["Hello", "World", "!"]
--   "Hello\nWorld\n!\n"
--   </pre>
unlines :: [String] -> String

-- | <a>unwords</a> is an inverse operation to <a>words</a>. It joins words
--   with separating spaces.
--   
--   <pre>
--   &gt;&gt;&gt; unwords ["Lorem", "ipsum", "dolor"]
--   "Lorem ipsum dolor"
--   </pre>
unwords :: [String] -> String

-- | <a>words</a> breaks a string up into a list of words, which were
--   delimited by white space.
--   
--   <pre>
--   &gt;&gt;&gt; words "Lorem ipsum\ndolor"
--   ["Lorem","ipsum","dolor"]
--   </pre>
words :: String -> [String]

-- | <a>curry</a> converts an uncurried function to a curried function.
--   
--   <h4><b>Examples</b></h4>
--   
--   <pre>
--   &gt;&gt;&gt; curry fst 1 2
--   1
--   </pre>
curry :: () => (a, b) -> c -> a -> b -> c

-- | Extract the first component of a pair.
fst :: () => (a, b) -> a

-- | Extract the second component of a pair.
snd :: () => (a, b) -> b

-- | <a>uncurry</a> converts a curried function to a function on pairs.
--   
--   <h4><b>Examples</b></h4>
--   
--   <pre>
--   &gt;&gt;&gt; uncurry (+) (1,2)
--   3
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; uncurry ($) (show, 1)
--   "1"
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; map (uncurry max) [(1,2), (3,4), (6,8)]
--   [2,4,8]
--   </pre>
uncurry :: () => a -> b -> c -> (a, b) -> c

-- | Strict (call-by-value) application operator. It takes a function and
--   an argument, evaluates the argument to weak head normal form (WHNF),
--   then calls the function with that value.
($!) :: forall r a (b :: TYPE r). (a -> b) -> a -> b
infixr 0 $!

-- | Append two lists, i.e.,
--   
--   <pre>
--   [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
--   [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
--   </pre>
--   
--   If the first list is not finite, the result is the first list.
(++) :: () => [a] -> [a] -> [a]
infixr 5 ++

-- | Function composition.
(.) :: () => b -> c -> a -> b -> a -> c
infixr 9 .

-- | Same as <a>&gt;&gt;=</a>, but with the arguments interchanged.
(=<<) :: Monad m => a -> m b -> m a -> m b
infixr 1 =<<

-- | <a>asTypeOf</a> is a type-restricted version of <a>const</a>. It is
--   usually used as an infix operator, and its typing forces its first
--   argument (which is usually overloaded) to have the same type as the
--   second.
asTypeOf :: () => a -> a -> a

-- | <tt>const x</tt> is a unary function which evaluates to <tt>x</tt> for
--   all inputs.
--   
--   <pre>
--   &gt;&gt;&gt; const 42 "hello"
--   42
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; map (const 42) [0..3]
--   [42,42,42,42]
--   </pre>
const :: () => a -> b -> a

-- | <tt><a>flip</a> f</tt> takes its (first) two arguments in the reverse
--   order of <tt>f</tt>.
--   
--   <pre>
--   &gt;&gt;&gt; flip (++) "hello" "world"
--   "worldhello"
--   </pre>
flip :: () => a -> b -> c -> b -> a -> c

-- | Identity function.
--   
--   <pre>
--   id x = x
--   </pre>
id :: () => a -> a

-- | <a>map</a> <tt>f xs</tt> is the list obtained by applying <tt>f</tt>
--   to each element of <tt>xs</tt>, i.e.,
--   
--   <pre>
--   map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
--   map f [x1, x2, ...] == [f x1, f x2, ...]
--   </pre>
map :: () => a -> b -> [a] -> [b]

-- | <a>otherwise</a> is defined as the value <a>True</a>. It helps to make
--   guards more readable. eg.
--   
--   <pre>
--   f x | x &lt; 0     = ...
--       | otherwise = ...
--   </pre>
otherwise :: Bool

-- | <tt><a>until</a> p f</tt> yields the result of applying <tt>f</tt>
--   until <tt>p</tt> holds.
until :: () => a -> Bool -> a -> a -> a -> a

-- | Raise an <a>IOError</a> in the <a>IO</a> monad.
ioError :: () => IOError -> IO a

-- | Construct an <a>IOError</a> value with a string describing the error.
--   The <a>fail</a> method of the <a>IO</a> instance of the <a>Monad</a>
--   class raises a <a>userError</a>, thus:
--   
--   <pre>
--   instance Monad IO where
--     ...
--     fail s = ioError (userError s)
--   </pre>
userError :: String -> IOError

-- | List index (subscript) operator, starting from 0. It is an instance of
--   the more general <a>genericIndex</a>, which takes an index of any
--   integral type.
(!!) :: () => [a] -> Int -> a
infixl 9 !!

-- | <a>break</a>, applied to a predicate <tt>p</tt> and a list
--   <tt>xs</tt>, returns a tuple where first element is longest prefix
--   (possibly empty) of <tt>xs</tt> of elements that <i>do not satisfy</i>
--   <tt>p</tt> and second element is the remainder of the list:
--   
--   <pre>
--   break (&gt; 3) [1,2,3,4,1,2,3,4] == ([1,2,3],[4,1,2,3,4])
--   break (&lt; 9) [1,2,3] == ([],[1,2,3])
--   break (&gt; 9) [1,2,3] == ([1,2,3],[])
--   </pre>
--   
--   <a>break</a> <tt>p</tt> is equivalent to <tt><a>span</a> (<a>not</a> .
--   p)</tt>.
break :: () => a -> Bool -> [a] -> ([a], [a])

-- | <a>cycle</a> ties a finite list into a circular one, or equivalently,
--   the infinite repetition of the original list. It is the identity on
--   infinite lists.
cycle :: () => [a] -> [a]

-- | <a>drop</a> <tt>n xs</tt> returns the suffix of <tt>xs</tt> after the
--   first <tt>n</tt> elements, or <tt>[]</tt> if <tt>n &gt; <a>length</a>
--   xs</tt>:
--   
--   <pre>
--   drop 6 "Hello World!" == "World!"
--   drop 3 [1,2,3,4,5] == [4,5]
--   drop 3 [1,2] == []
--   drop 3 [] == []
--   drop (-1) [1,2] == [1,2]
--   drop 0 [1,2] == [1,2]
--   </pre>
--   
--   It is an instance of the more general <a>genericDrop</a>, in which
--   <tt>n</tt> may be of any integral type.
drop :: () => Int -> [a] -> [a]

-- | <a>dropWhile</a> <tt>p xs</tt> returns the suffix remaining after
--   <a>takeWhile</a> <tt>p xs</tt>:
--   
--   <pre>
--   dropWhile (&lt; 3) [1,2,3,4,5,1,2,3] == [3,4,5,1,2,3]
--   dropWhile (&lt; 9) [1,2,3] == []
--   dropWhile (&lt; 0) [1,2,3] == [1,2,3]
--   </pre>
dropWhile :: () => a -> Bool -> [a] -> [a]

-- | <a>filter</a>, applied to a predicate and a list, returns the list of
--   those elements that satisfy the predicate; i.e.,
--   
--   <pre>
--   filter p xs = [ x | x &lt;- xs, p x]
--   </pre>
filter :: () => a -> Bool -> [a] -> [a]

-- | Extract the first element of a list, which must be non-empty.
head :: () => [a] -> a

-- | Return all the elements of a list except the last one. The list must
--   be non-empty.
init :: () => [a] -> [a]

-- | <a>iterate</a> <tt>f x</tt> returns an infinite list of repeated
--   applications of <tt>f</tt> to <tt>x</tt>:
--   
--   <pre>
--   iterate f x == [x, f x, f (f x), ...]
--   </pre>
--   
--   Note that <a>iterate</a> is lazy, potentially leading to thunk
--   build-up if the consumer doesn't force each iterate. See 'iterate\''
--   for a strict variant of this function.
iterate :: () => a -> a -> a -> [a]

-- | Extract the last element of a list, which must be finite and
--   non-empty.
last :: () => [a] -> a

-- | <a>lookup</a> <tt>key assocs</tt> looks up a key in an association
--   list.
lookup :: Eq a => a -> [(a, b)] -> Maybe b

-- | <a>repeat</a> <tt>x</tt> is an infinite list, with <tt>x</tt> the
--   value of every element.
repeat :: () => a -> [a]

-- | <a>replicate</a> <tt>n x</tt> is a list of length <tt>n</tt> with
--   <tt>x</tt> the value of every element. It is an instance of the more
--   general <a>genericReplicate</a>, in which <tt>n</tt> may be of any
--   integral type.
replicate :: () => Int -> a -> [a]

-- | <a>reverse</a> <tt>xs</tt> returns the elements of <tt>xs</tt> in
--   reverse order. <tt>xs</tt> must be finite.
reverse :: () => [a] -> [a]

-- | <a>scanl</a> is similar to <a>foldl</a>, but returns a list of
--   successive reduced values from the left:
--   
--   <pre>
--   scanl f z [x1, x2, ...] == [z, z `f` x1, (z `f` x1) `f` x2, ...]
--   </pre>
--   
--   Note that
--   
--   <pre>
--   last (scanl f z xs) == foldl f z xs.
--   </pre>
scanl :: () => b -> a -> b -> b -> [a] -> [b]

-- | <a>scanl1</a> is a variant of <a>scanl</a> that has no starting value
--   argument:
--   
--   <pre>
--   scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...]
--   </pre>
scanl1 :: () => a -> a -> a -> [a] -> [a]

-- | <a>scanr</a> is the right-to-left dual of <a>scanl</a>. Note that
--   
--   <pre>
--   head (scanr f z xs) == foldr f z xs.
--   </pre>
scanr :: () => a -> b -> b -> b -> [a] -> [b]

-- | <a>scanr1</a> is a variant of <a>scanr</a> that has no starting value
--   argument.
scanr1 :: () => a -> a -> a -> [a] -> [a]

-- | <a>span</a>, applied to a predicate <tt>p</tt> and a list <tt>xs</tt>,
--   returns a tuple where first element is longest prefix (possibly empty)
--   of <tt>xs</tt> of elements that satisfy <tt>p</tt> and second element
--   is the remainder of the list:
--   
--   <pre>
--   span (&lt; 3) [1,2,3,4,1,2,3,4] == ([1,2],[3,4,1,2,3,4])
--   span (&lt; 9) [1,2,3] == ([1,2,3],[])
--   span (&lt; 0) [1,2,3] == ([],[1,2,3])
--   </pre>
--   
--   <a>span</a> <tt>p xs</tt> is equivalent to <tt>(<a>takeWhile</a> p xs,
--   <a>dropWhile</a> p xs)</tt>
span :: () => a -> Bool -> [a] -> ([a], [a])

-- | <a>splitAt</a> <tt>n xs</tt> returns a tuple where first element is
--   <tt>xs</tt> prefix of length <tt>n</tt> and second element is the
--   remainder of the list:
--   
--   <pre>
--   splitAt 6 "Hello World!" == ("Hello ","World!")
--   splitAt 3 [1,2,3,4,5] == ([1,2,3],[4,5])
--   splitAt 1 [1,2,3] == ([1],[2,3])
--   splitAt 3 [1,2,3] == ([1,2,3],[])
--   splitAt 4 [1,2,3] == ([1,2,3],[])
--   splitAt 0 [1,2,3] == ([],[1,2,3])
--   splitAt (-1) [1,2,3] == ([],[1,2,3])
--   </pre>
--   
--   It is equivalent to <tt>(<a>take</a> n xs, <a>drop</a> n xs)</tt> when
--   <tt>n</tt> is not <tt>_|_</tt> (<tt>splitAt _|_ xs = _|_</tt>).
--   <a>splitAt</a> is an instance of the more general
--   <a>genericSplitAt</a>, in which <tt>n</tt> may be of any integral
--   type.
splitAt :: () => Int -> [a] -> ([a], [a])

-- | Extract the elements after the head of a list, which must be
--   non-empty.
tail :: () => [a] -> [a]

-- | <a>take</a> <tt>n</tt>, applied to a list <tt>xs</tt>, returns the
--   prefix of <tt>xs</tt> of length <tt>n</tt>, or <tt>xs</tt> itself if
--   <tt>n &gt; <a>length</a> xs</tt>:
--   
--   <pre>
--   take 5 "Hello World!" == "Hello"
--   take 3 [1,2,3,4,5] == [1,2,3]
--   take 3 [1,2] == [1,2]
--   take 3 [] == []
--   take (-1) [1,2] == []
--   take 0 [1,2] == []
--   </pre>
--   
--   It is an instance of the more general <a>genericTake</a>, in which
--   <tt>n</tt> may be of any integral type.
take :: () => Int -> [a] -> [a]

-- | <a>takeWhile</a>, applied to a predicate <tt>p</tt> and a list
--   <tt>xs</tt>, returns the longest prefix (possibly empty) of
--   <tt>xs</tt> of elements that satisfy <tt>p</tt>:
--   
--   <pre>
--   takeWhile (&lt; 3) [1,2,3,4,1,2,3,4] == [1,2]
--   takeWhile (&lt; 9) [1,2,3] == [1,2,3]
--   takeWhile (&lt; 0) [1,2,3] == []
--   </pre>
takeWhile :: () => a -> Bool -> [a] -> [a]

-- | <a>unzip</a> transforms a list of pairs into a list of first
--   components and a list of second components.
unzip :: () => [(a, b)] -> ([a], [b])

-- | The <a>unzip3</a> function takes a list of triples and returns three
--   lists, analogous to <a>unzip</a>.
unzip3 :: () => [(a, b, c)] -> ([a], [b], [c])

-- | <a>zip</a> takes two lists and returns a list of corresponding pairs.
--   If one input list is short, excess elements of the longer list are
--   discarded.
--   
--   <a>zip</a> is right-lazy:
--   
--   <pre>
--   zip [] _|_ = []
--   </pre>
zip :: () => [a] -> [b] -> [(a, b)]

-- | <a>zip3</a> takes three lists and returns a list of triples, analogous
--   to <a>zip</a>.
zip3 :: () => [a] -> [b] -> [c] -> [(a, b, c)]

-- | <a>zipWith</a> generalises <a>zip</a> by zipping with the function
--   given as the first argument, instead of a tupling function. For
--   example, <tt><a>zipWith</a> (+)</tt> is applied to two lists to
--   produce the list of corresponding sums.
--   
--   <a>zipWith</a> is right-lazy:
--   
--   <pre>
--   zipWith f [] _|_ = []
--   </pre>
zipWith :: () => a -> b -> c -> [a] -> [b] -> [c]

-- | The <a>zipWith3</a> function takes a function which combines three
--   elements, as well as three lists and returns a list of their
--   point-wise combination, analogous to <a>zipWith</a>.
zipWith3 :: () => a -> b -> c -> d -> [a] -> [b] -> [c] -> [d]

-- | the same as <tt><a>flip</a> (<a>-</a>)</tt>.
--   
--   Because <tt>-</tt> is treated specially in the Haskell grammar,
--   <tt>(-</tt> <i>e</i><tt>)</tt> is not a section, but an application of
--   prefix negation. However, <tt>(<a>subtract</a></tt>
--   <i>exp</i><tt>)</tt> is equivalent to the disallowed section.
subtract :: Num a => a -> a -> a

-- | The <a>lex</a> function reads a single lexeme from the input,
--   discarding initial white space, and returning the characters that
--   constitute the lexeme. If the input string contains only white space,
--   <a>lex</a> returns a single successful `lexeme' consisting of the
--   empty string. (Thus <tt><a>lex</a> "" = [("","")]</tt>.) If there is
--   no legal lexeme at the beginning of the input string, <a>lex</a> fails
--   (i.e. returns <tt>[]</tt>).
--   
--   This lexer is not completely faithful to the Haskell lexical syntax in
--   the following respects:
--   
--   <ul>
--   <li>Qualified names are not handled properly</li>
--   <li>Octal and hexadecimal numerics are not recognized as a single
--   token</li>
--   <li>Comments are not treated properly</li>
--   </ul>
lex :: ReadS String

-- | <tt><a>readParen</a> <a>True</a> p</tt> parses what <tt>p</tt> parses,
--   but surrounded with parentheses.
--   
--   <tt><a>readParen</a> <a>False</a> p</tt> parses what <tt>p</tt>
--   parses, but optionally surrounded with parentheses.
readParen :: () => Bool -> ReadS a -> ReadS a

-- | raise a number to a non-negative integral power
(^) :: (Num a, Integral b) => a -> b -> a
infixr 8 ^

-- | raise a number to an integral power
(^^) :: (Fractional a, Integral b) => a -> b -> a
infixr 8 ^^
even :: Integral a => a -> Bool

-- | general coercion from integral types
fromIntegral :: (Integral a, Num b) => a -> b

-- | <tt><a>gcd</a> x y</tt> is the non-negative factor of both <tt>x</tt>
--   and <tt>y</tt> of which every common factor of <tt>x</tt> and
--   <tt>y</tt> is also a factor; for example <tt><a>gcd</a> 4 2 = 2</tt>,
--   <tt><a>gcd</a> (-4) 6 = 2</tt>, <tt><a>gcd</a> 0 4</tt> = <tt>4</tt>.
--   <tt><a>gcd</a> 0 0</tt> = <tt>0</tt>. (That is, the common divisor
--   that is "greatest" in the divisibility preordering.)
--   
--   Note: Since for signed fixed-width integer types, <tt><a>abs</a>
--   <a>minBound</a> &lt; 0</tt>, the result may be negative if one of the
--   arguments is <tt><a>minBound</a></tt> (and necessarily is if the other
--   is <tt>0</tt> or <tt><a>minBound</a></tt>) for such types.
gcd :: Integral a => a -> a -> a

-- | <tt><a>lcm</a> x y</tt> is the smallest positive integer that both
--   <tt>x</tt> and <tt>y</tt> divide.
lcm :: Integral a => a -> a -> a
odd :: Integral a => a -> Bool

-- | general coercion to fractional types
realToFrac :: (Real a, Fractional b) => a -> b

-- | utility function converting a <a>Char</a> to a show function that
--   simply prepends the character unchanged.
showChar :: Char -> ShowS

-- | utility function that surrounds the inner show function with
--   parentheses when the <a>Bool</a> parameter is <a>True</a>.
showParen :: Bool -> ShowS -> ShowS

-- | utility function converting a <a>String</a> to a show function that
--   simply prepends the string unchanged.
showString :: String -> ShowS

-- | equivalent to <a>showsPrec</a> with a precedence of 0.
shows :: Show a => a -> ShowS

-- | The computation <a>appendFile</a> <tt>file str</tt> function appends
--   the string <tt>str</tt>, to the file <tt>file</tt>.
--   
--   Note that <a>writeFile</a> and <a>appendFile</a> write a literal
--   string to a file. To write a value of any printable type, as with
--   <a>print</a>, use the <a>show</a> function to convert the value to a
--   string first.
--   
--   <pre>
--   main = appendFile "squares" (show [(x,x*x) | x &lt;- [0,0.1..2]])
--   </pre>
appendFile :: FilePath -> String -> IO ()

-- | Read a character from the standard input device (same as
--   <a>hGetChar</a> <a>stdin</a>).
getChar :: IO Char

-- | The <a>getContents</a> operation returns all user input as a single
--   string, which is read lazily as it is needed (same as
--   <a>hGetContents</a> <a>stdin</a>).
getContents :: IO String

-- | Read a line from the standard input device (same as <a>hGetLine</a>
--   <a>stdin</a>).
getLine :: IO String

-- | The <a>interact</a> function takes a function of type
--   <tt>String-&gt;String</tt> as its argument. The entire input from the
--   standard input device is passed to this function as its argument, and
--   the resulting string is output on the standard output device.
interact :: String -> String -> IO ()

-- | The <a>print</a> function outputs a value of any printable type to the
--   standard output device. Printable types are those that are instances
--   of class <a>Show</a>; <a>print</a> converts values to strings for
--   output using the <a>show</a> operation and adds a newline.
--   
--   For example, a program to print the first 20 integers and their powers
--   of 2 could be written as:
--   
--   <pre>
--   main = print ([(n, 2^n) | n &lt;- [0..19]])
--   </pre>
print :: Show a => a -> IO ()

-- | Write a character to the standard output device (same as
--   <a>hPutChar</a> <a>stdout</a>).
putChar :: Char -> IO ()

-- | Write a string to the standard output device (same as <a>hPutStr</a>
--   <a>stdout</a>).
putStr :: String -> IO ()

-- | The same as <a>putStr</a>, but adds a newline character.
putStrLn :: String -> IO ()

-- | The <a>readFile</a> function reads a file and returns the contents of
--   the file as a string. The file is read lazily, on demand, as with
--   <a>getContents</a>.
readFile :: FilePath -> IO String

-- | The <a>readIO</a> function is similar to <a>read</a> except that it
--   signals parse failure to the <a>IO</a> monad instead of terminating
--   the program.
readIO :: Read a => String -> IO a

-- | The <a>readLn</a> function combines <a>getLine</a> and <a>readIO</a>.
readLn :: Read a => IO a

-- | The computation <a>writeFile</a> <tt>file str</tt> function writes the
--   string <tt>str</tt>, to the file <tt>file</tt>.
writeFile :: FilePath -> String -> IO ()

-- | The <a>read</a> function reads input from a string, which must be
--   completely consumed by the input process. <a>read</a> fails with an
--   <a>error</a> if the parse is unsuccessful, and it is therefore
--   discouraged from being used in real applications. Use <a>readMaybe</a>
--   or <a>readEither</a> for safe alternatives.
--   
--   <pre>
--   &gt;&gt;&gt; read "123" :: Int
--   123
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; read "hello" :: Int
--   *** Exception: Prelude.read: no parse
--   </pre>
read :: Read a => String -> a

-- | equivalent to <a>readsPrec</a> with a precedence of 0.
reads :: Read a => ReadS a

-- | Boolean "and"
(&&) :: Bool -> Bool -> Bool
infixr 3 &&

-- | Boolean "not"
not :: Bool -> Bool

-- | Boolean "or"
(||) :: Bool -> Bool -> Bool
infixr 2 ||

-- | Application operator. This operator is redundant, since ordinary
--   application <tt>(f x)</tt> means the same as <tt>(f <a>$</a> x)</tt>.
--   However, <a>$</a> has low, right-associative binding precedence, so it
--   sometimes allows parentheses to be omitted; for example:
--   
--   <pre>
--   f $ g $ h x  =  f (g (h x))
--   </pre>
--   
--   It is also useful in higher-order situations, such as <tt><a>map</a>
--   (<a>$</a> 0) xs</tt>, or <tt><a>zipWith</a> (<a>$</a>) fs xs</tt>.
($) :: () => a -> b -> a -> b
infixr 0 $

-- | <a>error</a> stops execution and displays an error message.
error :: HasCallStack => [Char] -> a

-- | A variant of <a>error</a> that does not produce a stack trace.
errorWithoutStackTrace :: () => [Char] -> a

-- | A special case of <a>error</a>. It is expected that compilers will
--   recognize this and insert error messages which are more appropriate to
--   the context in which <a>undefined</a> appears.
undefined :: HasCallStack => a

-- | The value of <tt>seq a b</tt> is bottom if <tt>a</tt> is bottom, and
--   otherwise equal to <tt>b</tt>. In other words, it evaluates the first
--   argument <tt>a</tt> to weak head normal form (WHNF). <tt>seq</tt> is
--   usually introduced to improve performance by avoiding unneeded
--   laziness.
--   
--   A note on evaluation order: the expression <tt>seq a b</tt> does
--   <i>not</i> guarantee that <tt>a</tt> will be evaluated before
--   <tt>b</tt>. The only guarantee given by <tt>seq</tt> is that the both
--   <tt>a</tt> and <tt>b</tt> will be evaluated before <tt>seq</tt>
--   returns a value. In particular, this means that <tt>b</tt> may be
--   evaluated before <tt>a</tt>. If you need to guarantee a specific order
--   of evaluation, you must use the function <tt>pseq</tt> from the
--   "parallel" package.
seq :: () => a -> b -> b

-- | Does the element occur in the structure?
elem :: (Foldable t, Eq a) => a -> t a -> Bool
infix 4 `elem`

-- | Map each element of the structure to a monoid, and combine the
--   results.
foldMap :: (Foldable t, Monoid m) => a -> m -> t a -> m

-- | Left-associative fold of a structure.
--   
--   In the case of lists, <a>foldl</a>, when applied to a binary operator,
--   a starting value (typically the left-identity of the operator), and a
--   list, reduces the list using the binary operator, from left to right:
--   
--   <pre>
--   foldl f z [x1, x2, ..., xn] == (...((z `f` x1) `f` x2) `f`...) `f` xn
--   </pre>
--   
--   Note that to produce the outermost application of the operator the
--   entire input list must be traversed. This means that <a>foldl'</a>
--   will diverge if given an infinite list.
--   
--   Also note that if you want an efficient left-fold, you probably want
--   to use <a>foldl'</a> instead of <a>foldl</a>. The reason for this is
--   that latter does not force the "inner" results (e.g. <tt>z <tt>f</tt>
--   x1</tt> in the above example) before applying them to the operator
--   (e.g. to <tt>(<tt>f</tt> x2)</tt>). This results in a thunk chain
--   <tt>O(n)</tt> elements long, which then must be evaluated from the
--   outside-in.
--   
--   For a general <a>Foldable</a> structure this should be semantically
--   identical to,
--   
--   <pre>
--   foldl f z = <a>foldl</a> f z . <a>toList</a>
--   </pre>
foldl :: Foldable t => b -> a -> b -> b -> t a -> b

-- | A variant of <a>foldl</a> that has no base case, and thus may only be
--   applied to non-empty structures.
--   
--   <pre>
--   <a>foldl1</a> f = <a>foldl1</a> f . <a>toList</a>
--   </pre>
foldl1 :: Foldable t => a -> a -> a -> t a -> a

-- | Right-associative fold of a structure.
--   
--   In the case of lists, <a>foldr</a>, when applied to a binary operator,
--   a starting value (typically the right-identity of the operator), and a
--   list, reduces the list using the binary operator, from right to left:
--   
--   <pre>
--   foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
--   </pre>
--   
--   Note that, since the head of the resulting expression is produced by
--   an application of the operator to the first element of the list,
--   <a>foldr</a> can produce a terminating expression from an infinite
--   list.
--   
--   For a general <a>Foldable</a> structure this should be semantically
--   identical to,
--   
--   <pre>
--   foldr f z = <a>foldr</a> f z . <a>toList</a>
--   </pre>
foldr :: Foldable t => a -> b -> b -> b -> t a -> b

-- | A variant of <a>foldr</a> that has no base case, and thus may only be
--   applied to non-empty structures.
--   
--   <pre>
--   <a>foldr1</a> f = <a>foldr1</a> f . <a>toList</a>
--   </pre>
foldr1 :: Foldable t => a -> a -> a -> t a -> a

-- | Returns the size/length of a finite structure as an <a>Int</a>. The
--   default implementation is optimized for structures that are similar to
--   cons-lists, because there is no general way to do better.
length :: Foldable t => t a -> Int

-- | The largest element of a non-empty structure.
maximum :: (Foldable t, Ord a) => t a -> a

-- | The least element of a non-empty structure.
minimum :: (Foldable t, Ord a) => t a -> a

-- | Test whether the structure is empty. The default implementation is
--   optimized for structures that are similar to cons-lists, because there
--   is no general way to do better.
null :: Foldable t => t a -> Bool

-- | The <a>product</a> function computes the product of the numbers of a
--   structure.
product :: (Foldable t, Num a) => t a -> a

-- | The <a>sum</a> function computes the sum of the numbers of a
--   structure.
sum :: (Foldable t, Num a) => t a -> a

-- | Map each element of a structure to a monadic action, evaluate these
--   actions from left to right, and collect the results. For a version
--   that ignores the results see <a>mapM_</a>.
mapM :: (Traversable t, Monad m) => a -> m b -> t a -> m t b

-- | Evaluate each monadic action in the structure from left to right, and
--   collect the results. For a version that ignores the results see
--   <a>sequence_</a>.
sequence :: (Traversable t, Monad m) => t m a -> m t a

-- | Evaluate each action in the structure from left to right, and and
--   collect the results. For a version that ignores the results see
--   <a>sequenceA_</a>.
sequenceA :: (Traversable t, Applicative f) => t f a -> f t a

-- | Map each element of a structure to an action, evaluate these actions
--   from left to right, and collect the results. For a version that
--   ignores the results see <a>traverse_</a>.
traverse :: (Traversable t, Applicative f) => a -> f b -> t a -> f t b

-- | Sequence actions, discarding the value of the first argument.
(*>) :: Applicative f => f a -> f b -> f b
infixl 4 *>

-- | Sequence actions, discarding the value of the second argument.
(<*) :: Applicative f => f a -> f b -> f a
infixl 4 <*

-- | Sequential application.
--   
--   A few functors support an implementation of <a>&lt;*&gt;</a> that is
--   more efficient than the default one.
(<*>) :: Applicative f => f a -> b -> f a -> f b
infixl 4 <*>

-- | Lift a value.
pure :: Applicative f => a -> f a

-- | Replace all locations in the input with the same value. The default
--   definition is <tt><a>fmap</a> . <a>const</a></tt>, but this may be
--   overridden with a more efficient version.
(<$) :: Functor f => a -> f b -> f a
infixl 4 <$
fmap :: Functor f => a -> b -> f a -> f b

-- | Sequentially compose two actions, discarding any value produced by the
--   first, like sequencing operators (such as the semicolon) in imperative
--   languages.
(>>) :: Monad m => m a -> m b -> m b
infixl 1 >>

-- | Sequentially compose two actions, passing any value produced by the
--   first as an argument to the second.
(>>=) :: Monad m => m a -> a -> m b -> m b
infixl 1 >>=

-- | Fail with a message. This operation is not part of the mathematical
--   definition of a monad, but is invoked on pattern-match failure in a
--   <tt>do</tt> expression.
--   
--   As part of the MonadFail proposal (MFP), this function is moved to its
--   own class <tt>MonadFail</tt> (see <a>Control.Monad.Fail</a> for more
--   details). The definition here will be removed in a future release.
fail :: Monad m => String -> m a

-- | Inject a value into the monadic type.
return :: Monad m => a -> m a

-- | An associative operation
--   
--   <b>NOTE</b>: This method is redundant and has the default
--   implementation <tt><a>mappend</a> = '(&lt;&gt;)'</tt> since
--   <i>base-4.11.0.0</i>.
mappend :: Monoid a => a -> a -> a

-- | Fold a list using the monoid.
--   
--   For most types, the default definition for <a>mconcat</a> will be
--   used, but the function is included in the class definition so that an
--   optimized version can be provided for specific types.
mconcat :: Monoid a => [a] -> a

-- | Identity of <a>mappend</a>
mempty :: Monoid a => a

-- | An associative operation.
(<>) :: Semigroup a => a -> a -> a
infixr 6 <>
maxBound :: Bounded a => a
minBound :: Bounded a => a

-- | Used in Haskell's translation of <tt>[n..]</tt>.
enumFrom :: Enum a => a -> [a]

-- | Used in Haskell's translation of <tt>[n,n'..]</tt>.
enumFromThen :: Enum a => a -> a -> [a]

-- | Used in Haskell's translation of <tt>[n,n'..m]</tt>.
enumFromThenTo :: Enum a => a -> a -> a -> [a]

-- | Used in Haskell's translation of <tt>[n..m]</tt>.
enumFromTo :: Enum a => a -> a -> [a]

-- | Convert to an <a>Int</a>. It is implementation-dependent what
--   <a>fromEnum</a> returns when applied to a value that is too large to
--   fit in an <a>Int</a>.
fromEnum :: Enum a => a -> Int

-- | the predecessor of a value. For numeric types, <a>pred</a> subtracts
--   1.
pred :: Enum a => a -> a

-- | the successor of a value. For numeric types, <a>succ</a> adds 1.
succ :: Enum a => a -> a

-- | Convert from an <a>Int</a>.
toEnum :: Enum a => Int -> a
(**) :: Floating a => a -> a -> a
infixr 8 **
acos :: Floating a => a -> a
acosh :: Floating a => a -> a
asin :: Floating a => a -> a
asinh :: Floating a => a -> a
atan :: Floating a => a -> a
atanh :: Floating a => a -> a
cos :: Floating a => a -> a
cosh :: Floating a => a -> a
exp :: Floating a => a -> a
log :: Floating a => a -> a
logBase :: Floating a => a -> a -> a
pi :: Floating a => a
sin :: Floating a => a -> a
sinh :: Floating a => a -> a
sqrt :: Floating a => a -> a
tan :: Floating a => a -> a
tanh :: Floating a => a -> a

-- | a version of arctangent taking two real floating-point arguments. For
--   real floating <tt>x</tt> and <tt>y</tt>, <tt><a>atan2</a> y x</tt>
--   computes the angle (from the positive x-axis) of the vector from the
--   origin to the point <tt>(x,y)</tt>. <tt><a>atan2</a> y x</tt> returns
--   a value in the range [<tt>-pi</tt>, <tt>pi</tt>]. It follows the
--   Common Lisp semantics for the origin when signed zeroes are supported.
--   <tt><a>atan2</a> y 1</tt>, with <tt>y</tt> in a type that is
--   <a>RealFloat</a>, should return the same value as <tt><a>atan</a>
--   y</tt>. A default definition of <a>atan2</a> is provided, but
--   implementors can provide a more accurate implementation.
atan2 :: RealFloat a => a -> a -> a

-- | The function <a>decodeFloat</a> applied to a real floating-point
--   number returns the significand expressed as an <a>Integer</a> and an
--   appropriately scaled exponent (an <a>Int</a>). If
--   <tt><a>decodeFloat</a> x</tt> yields <tt>(m,n)</tt>, then <tt>x</tt>
--   is equal in value to <tt>m*b^^n</tt>, where <tt>b</tt> is the
--   floating-point radix, and furthermore, either <tt>m</tt> and
--   <tt>n</tt> are both zero or else <tt>b^(d-1) &lt;= <a>abs</a> m &lt;
--   b^d</tt>, where <tt>d</tt> is the value of <tt><a>floatDigits</a>
--   x</tt>. In particular, <tt><a>decodeFloat</a> 0 = (0,0)</tt>. If the
--   type contains a negative zero, also <tt><a>decodeFloat</a> (-0.0) =
--   (0,0)</tt>. <i>The result of</i> <tt><a>decodeFloat</a> x</tt> <i>is
--   unspecified if either of</i> <tt><a>isNaN</a> x</tt> <i>or</i>
--   <tt><a>isInfinite</a> x</tt> <i>is</i> <a>True</a>.
decodeFloat :: RealFloat a => a -> (Integer, Int)

-- | <a>encodeFloat</a> performs the inverse of <a>decodeFloat</a> in the
--   sense that for finite <tt>x</tt> with the exception of <tt>-0.0</tt>,
--   <tt><tt>uncurry</tt> <a>encodeFloat</a> (<a>decodeFloat</a> x) =
--   x</tt>. <tt><a>encodeFloat</a> m n</tt> is one of the two closest
--   representable floating-point numbers to <tt>m*b^^n</tt> (or
--   <tt>±Infinity</tt> if overflow occurs); usually the closer, but if
--   <tt>m</tt> contains too many bits, the result may be rounded in the
--   wrong direction.
encodeFloat :: RealFloat a => Integer -> Int -> a

-- | <a>exponent</a> corresponds to the second component of
--   <a>decodeFloat</a>. <tt><a>exponent</a> 0 = 0</tt> and for finite
--   nonzero <tt>x</tt>, <tt><a>exponent</a> x = snd (<a>decodeFloat</a> x)
--   + <a>floatDigits</a> x</tt>. If <tt>x</tt> is a finite floating-point
--   number, it is equal in value to <tt><a>significand</a> x * b ^^
--   <a>exponent</a> x</tt>, where <tt>b</tt> is the floating-point radix.
--   The behaviour is unspecified on infinite or <tt>NaN</tt> values.
exponent :: RealFloat a => a -> Int

-- | a constant function, returning the number of digits of
--   <a>floatRadix</a> in the significand
floatDigits :: RealFloat a => a -> Int

-- | a constant function, returning the radix of the representation (often
--   <tt>2</tt>)
floatRadix :: RealFloat a => a -> Integer

-- | a constant function, returning the lowest and highest values the
--   exponent may assume
floatRange :: RealFloat a => a -> (Int, Int)

-- | <a>True</a> if the argument is too small to be represented in
--   normalized format
isDenormalized :: RealFloat a => a -> Bool

-- | <a>True</a> if the argument is an IEEE floating point number
isIEEE :: RealFloat a => a -> Bool

-- | <a>True</a> if the argument is an IEEE infinity or negative infinity
isInfinite :: RealFloat a => a -> Bool

-- | <a>True</a> if the argument is an IEEE "not-a-number" (NaN) value
isNaN :: RealFloat a => a -> Bool

-- | <a>True</a> if the argument is an IEEE negative zero
isNegativeZero :: RealFloat a => a -> Bool

-- | multiplies a floating-point number by an integer power of the radix
scaleFloat :: RealFloat a => Int -> a -> a

-- | The first component of <a>decodeFloat</a>, scaled to lie in the open
--   interval (<tt>-1</tt>,<tt>1</tt>), either <tt>0.0</tt> or of absolute
--   value <tt>&gt;= 1/b</tt>, where <tt>b</tt> is the floating-point
--   radix. The behaviour is unspecified on infinite or <tt>NaN</tt>
--   values.
significand :: RealFloat a => a -> a
(*) :: Num a => a -> a -> a
infixl 7 *
(+) :: Num a => a -> a -> a
infixl 6 +
(-) :: Num a => a -> a -> a
infixl 6 -

-- | Absolute value.
abs :: Num a => a -> a

-- | Unary negation.
negate :: Num a => a -> a

-- | Sign of a number. The functions <a>abs</a> and <a>signum</a> should
--   satisfy the law:
--   
--   <pre>
--   abs x * signum x == x
--   </pre>
--   
--   For real numbers, the <a>signum</a> is either <tt>-1</tt> (negative),
--   <tt>0</tt> (zero) or <tt>1</tt> (positive).
signum :: Num a => a -> a

-- | The method <a>readList</a> is provided to allow the programmer to give
--   a specialised way of parsing lists of values. For example, this is
--   used by the predefined <a>Read</a> instance of the <a>Char</a> type,
--   where values of type <a>String</a> should be are expected to use
--   double quotes, rather than square brackets.
readList :: Read a => ReadS [a]

-- | attempts to parse a value from the front of the string, returning a
--   list of (parsed value, remaining string) pairs. If there is no
--   successful parse, the returned list is empty.
--   
--   Derived instances of <a>Read</a> and <a>Show</a> satisfy the
--   following:
--   
--   <ul>
--   <li><tt>(x,"")</tt> is an element of <tt>(<a>readsPrec</a> d
--   (<a>showsPrec</a> d x ""))</tt>.</li>
--   </ul>
--   
--   That is, <a>readsPrec</a> parses the string produced by
--   <a>showsPrec</a>, and delivers the value that <a>showsPrec</a> started
--   with.
readsPrec :: Read a => Int -> ReadS a

-- | fractional division
(/) :: Fractional a => a -> a -> a
infixl 7 /

-- | Conversion from a <a>Rational</a> (that is <tt><a>Ratio</a>
--   <a>Integer</a></tt>). A floating literal stands for an application of
--   <a>fromRational</a> to a value of type <a>Rational</a>, so such
--   literals have type <tt>(<a>Fractional</a> a) =&gt; a</tt>.
fromRational :: Fractional a => Rational -> a

-- | reciprocal fraction
recip :: Fractional a => a -> a

-- | integer division truncated toward negative infinity
div :: Integral a => a -> a -> a
infixl 7 `div`

-- | simultaneous <a>div</a> and <a>mod</a>
divMod :: Integral a => a -> a -> (a, a)

-- | integer modulus, satisfying
--   
--   <pre>
--   (x `div` y)*y + (x `mod` y) == x
--   </pre>
mod :: Integral a => a -> a -> a
infixl 7 `mod`

-- | integer division truncated toward zero
quot :: Integral a => a -> a -> a
infixl 7 `quot`

-- | simultaneous <a>quot</a> and <a>rem</a>
quotRem :: Integral a => a -> a -> (a, a)

-- | integer remainder, satisfying
--   
--   <pre>
--   (x `quot` y)*y + (x `rem` y) == x
--   </pre>
rem :: Integral a => a -> a -> a
infixl 7 `rem`

-- | conversion to <a>Integer</a>
toInteger :: Integral a => a -> Integer

-- | the rational equivalent of its real argument with full precision
toRational :: Real a => a -> Rational

-- | <tt><a>ceiling</a> x</tt> returns the least integer not less than
--   <tt>x</tt>
ceiling :: (RealFrac a, Integral b) => a -> b

-- | <tt><a>floor</a> x</tt> returns the greatest integer not greater than
--   <tt>x</tt>
floor :: (RealFrac a, Integral b) => a -> b

-- | The function <a>properFraction</a> takes a real fractional number
--   <tt>x</tt> and returns a pair <tt>(n,f)</tt> such that <tt>x =
--   n+f</tt>, and:
--   
--   <ul>
--   <li><tt>n</tt> is an integral number with the same sign as <tt>x</tt>;
--   and</li>
--   <li><tt>f</tt> is a fraction with the same type and sign as
--   <tt>x</tt>, and with absolute value less than <tt>1</tt>.</li>
--   </ul>
--   
--   The default definitions of the <a>ceiling</a>, <a>floor</a>,
--   <a>truncate</a> and <a>round</a> functions are in terms of
--   <a>properFraction</a>.
properFraction :: (RealFrac a, Integral b) => a -> (b, a)

-- | <tt><a>round</a> x</tt> returns the nearest integer to <tt>x</tt>; the
--   even integer if <tt>x</tt> is equidistant between two integers
round :: (RealFrac a, Integral b) => a -> b

-- | <tt><a>truncate</a> x</tt> returns the integer nearest <tt>x</tt>
--   between zero and <tt>x</tt>
truncate :: (RealFrac a, Integral b) => a -> b

-- | A specialised variant of <a>showsPrec</a>, using precedence context
--   zero, and returning an ordinary <a>String</a>.
show :: Show a => a -> String

-- | The method <a>showList</a> is provided to allow the programmer to give
--   a specialised way of showing lists of values. For example, this is
--   used by the predefined <a>Show</a> instance of the <a>Char</a> type,
--   where values of type <a>String</a> should be shown in double quotes,
--   rather than between square brackets.
showList :: Show a => [a] -> ShowS

-- | Convert a value to a readable <a>String</a>.
--   
--   <a>showsPrec</a> should satisfy the law
--   
--   <pre>
--   showsPrec d x r ++ s  ==  showsPrec d x (r ++ s)
--   </pre>
--   
--   Derived instances of <a>Read</a> and <a>Show</a> satisfy the
--   following:
--   
--   <ul>
--   <li><tt>(x,"")</tt> is an element of <tt>(<a>readsPrec</a> d
--   (<a>showsPrec</a> d x ""))</tt>.</li>
--   </ul>
--   
--   That is, <a>readsPrec</a> parses the string produced by
--   <a>showsPrec</a>, and delivers the value that <a>showsPrec</a> started
--   with.
showsPrec :: Show a => Int -> a -> ShowS
(/=) :: Eq a => a -> a -> Bool
infix 4 /=
(==) :: Eq a => a -> a -> Bool
infix 4 ==
(<) :: Ord a => a -> a -> Bool
infix 4 <
(<=) :: Ord a => a -> a -> Bool
infix 4 <=
(>) :: Ord a => a -> a -> Bool
infix 4 >
(>=) :: Ord a => a -> a -> Bool
infix 4 >=
compare :: Ord a => a -> a -> Ordering
max :: Ord a => a -> a -> a
min :: Ord a => a -> a -> a

-- | A functor with application, providing operations to
--   
--   <ul>
--   <li>embed pure expressions (<a>pure</a>), and</li>
--   <li>sequence computations and combine their results (<a>&lt;*&gt;</a>
--   and <a>liftA2</a>).</li>
--   </ul>
--   
--   A minimal complete definition must include implementations of
--   <a>pure</a> and of either <a>&lt;*&gt;</a> or <a>liftA2</a>. If it
--   defines both, then they must behave the same as their default
--   definitions:
--   
--   <pre>
--   (<a>&lt;*&gt;</a>) = <a>liftA2</a> <a>id</a>
--   </pre>
--   
--   <pre>
--   <a>liftA2</a> f x y = f <tt>&lt;$&gt;</tt> x <a>&lt;*&gt;</a> y
--   </pre>
--   
--   Further, any definition must satisfy the following:
--   
--   <ul>
--   <li><i><i>identity</i></i> <pre><a>pure</a> <a>id</a> <a>&lt;*&gt;</a>
--   v = v</pre></li>
--   <li><i><i>composition</i></i> <pre><a>pure</a> (.) <a>&lt;*&gt;</a> u
--   <a>&lt;*&gt;</a> v <a>&lt;*&gt;</a> w = u <a>&lt;*&gt;</a> (v
--   <a>&lt;*&gt;</a> w)</pre></li>
--   <li><i><i>homomorphism</i></i> <pre><a>pure</a> f <a>&lt;*&gt;</a>
--   <a>pure</a> x = <a>pure</a> (f x)</pre></li>
--   <li><i><i>interchange</i></i> <pre>u <a>&lt;*&gt;</a> <a>pure</a> y =
--   <a>pure</a> (<a>$</a> y) <a>&lt;*&gt;</a> u</pre></li>
--   </ul>
--   
--   The other methods have the following default definitions, which may be
--   overridden with equivalent specialized implementations:
--   
--   <ul>
--   <li><pre>u <a>*&gt;</a> v = (<a>id</a> <a>&lt;$</a> u)
--   <a>&lt;*&gt;</a> v</pre></li>
--   <li><pre>u <a>&lt;*</a> v = <a>liftA2</a> <a>const</a> u v</pre></li>
--   </ul>
--   
--   As a consequence of these laws, the <a>Functor</a> instance for
--   <tt>f</tt> will satisfy
--   
--   <ul>
--   <li><pre><a>fmap</a> f x = <a>pure</a> f <a>&lt;*&gt;</a> x</pre></li>
--   </ul>
--   
--   It may be useful to note that supposing
--   
--   <pre>
--   forall x y. p (q x y) = f x . g y
--   </pre>
--   
--   it follows from the above that
--   
--   <pre>
--   <a>liftA2</a> p (<a>liftA2</a> q u v) = <a>liftA2</a> f u . <a>liftA2</a> g v
--   </pre>
--   
--   If <tt>f</tt> is also a <a>Monad</a>, it should satisfy
--   
--   <ul>
--   <li><pre><a>pure</a> = <a>return</a></pre></li>
--   <li><pre>(<a>&lt;*&gt;</a>) = <a>ap</a></pre></li>
--   <li><pre>(<a>*&gt;</a>) = (<a>&gt;&gt;</a>)</pre></li>
--   </ul>
--   
--   (which implies that <a>pure</a> and <a>&lt;*&gt;</a> satisfy the
--   applicative functor laws).
class Functor f => Applicative (f :: * -> *)

-- | The <a>Bounded</a> class is used to name the upper and lower limits of
--   a type. <a>Ord</a> is not a superclass of <a>Bounded</a> since types
--   that are not totally ordered may also have upper and lower bounds.
--   
--   The <a>Bounded</a> class may be derived for any enumeration type;
--   <a>minBound</a> is the first constructor listed in the <tt>data</tt>
--   declaration and <a>maxBound</a> is the last. <a>Bounded</a> may also
--   be derived for single-constructor datatypes whose constituent types
--   are in <a>Bounded</a>.
class Bounded a

-- | Class <a>Enum</a> defines operations on sequentially ordered types.
--   
--   The <tt>enumFrom</tt>... methods are used in Haskell's translation of
--   arithmetic sequences.
--   
--   Instances of <a>Enum</a> may be derived for any enumeration type
--   (types whose constructors have no fields). The nullary constructors
--   are assumed to be numbered left-to-right by <a>fromEnum</a> from
--   <tt>0</tt> through <tt>n-1</tt>. See Chapter 10 of the <i>Haskell
--   Report</i> for more details.
--   
--   For any type that is an instance of class <a>Bounded</a> as well as
--   <a>Enum</a>, the following should hold:
--   
--   <ul>
--   <li>The calls <tt><a>succ</a> <a>maxBound</a></tt> and <tt><a>pred</a>
--   <a>minBound</a></tt> should result in a runtime error.</li>
--   <li><a>fromEnum</a> and <a>toEnum</a> should give a runtime error if
--   the result value is not representable in the result type. For example,
--   <tt><a>toEnum</a> 7 :: <a>Bool</a></tt> is an error.</li>
--   <li><a>enumFrom</a> and <a>enumFromThen</a> should be defined with an
--   implicit bound, thus:</li>
--   </ul>
--   
--   <pre>
--   enumFrom     x   = enumFromTo     x maxBound
--   enumFromThen x y = enumFromThenTo x y bound
--     where
--       bound | fromEnum y &gt;= fromEnum x = maxBound
--             | otherwise                = minBound
--   </pre>
class Enum a

-- | The <a>Eq</a> class defines equality (<a>==</a>) and inequality
--   (<a>/=</a>). All the basic datatypes exported by the <a>Prelude</a>
--   are instances of <a>Eq</a>, and <a>Eq</a> may be derived for any
--   datatype whose constituents are also instances of <a>Eq</a>.
--   
--   Minimal complete definition: either <a>==</a> or <a>/=</a>.
class Eq a

-- | Trigonometric and hyperbolic functions and related functions.
class Fractional a => Floating a

-- | Data structures that can be folded.
--   
--   For example, given a data type
--   
--   <pre>
--   data Tree a = Empty | Leaf a | Node (Tree a) a (Tree a)
--   </pre>
--   
--   a suitable instance would be
--   
--   <pre>
--   instance Foldable Tree where
--      foldMap f Empty = mempty
--      foldMap f (Leaf x) = f x
--      foldMap f (Node l k r) = foldMap f l `mappend` f k `mappend` foldMap f r
--   </pre>
--   
--   This is suitable even for abstract types, as the monoid is assumed to
--   satisfy the monoid laws. Alternatively, one could define
--   <tt>foldr</tt>:
--   
--   <pre>
--   instance Foldable Tree where
--      foldr f z Empty = z
--      foldr f z (Leaf x) = f x z
--      foldr f z (Node l k r) = foldr f (f k (foldr f z r)) l
--   </pre>
--   
--   <tt>Foldable</tt> instances are expected to satisfy the following
--   laws:
--   
--   <pre>
--   foldr f z t = appEndo (foldMap (Endo . f) t ) z
--   </pre>
--   
--   <pre>
--   foldl f z t = appEndo (getDual (foldMap (Dual . Endo . flip f) t)) z
--   </pre>
--   
--   <pre>
--   fold = foldMap id
--   </pre>
--   
--   <pre>
--   length = getSum . foldMap (Sum . const  1)
--   </pre>
--   
--   <tt>sum</tt>, <tt>product</tt>, <tt>maximum</tt>, and <tt>minimum</tt>
--   should all be essentially equivalent to <tt>foldMap</tt> forms, such
--   as
--   
--   <pre>
--   sum = getSum . foldMap Sum
--   </pre>
--   
--   but may be less defined.
--   
--   If the type is also a <a>Functor</a> instance, it should satisfy
--   
--   <pre>
--   foldMap f = fold . fmap f
--   </pre>
--   
--   which implies that
--   
--   <pre>
--   foldMap f . fmap g = foldMap (f . g)
--   </pre>
class Foldable (t :: * -> *)

-- | Fractional numbers, supporting real division.
class Num a => Fractional a

-- | The <a>Functor</a> class is used for types that can be mapped over.
--   Instances of <a>Functor</a> should satisfy the following laws:
--   
--   <pre>
--   fmap id  ==  id
--   fmap (f . g)  ==  fmap f . fmap g
--   </pre>
--   
--   The instances of <a>Functor</a> for lists, <a>Maybe</a> and <a>IO</a>
--   satisfy these laws.
class Functor (f :: * -> *)

-- | Integral numbers, supporting integer division.
class (Real a, Enum a) => Integral a

-- | The <a>Monad</a> class defines the basic operations over a
--   <i>monad</i>, a concept from a branch of mathematics known as
--   <i>category theory</i>. From the perspective of a Haskell programmer,
--   however, it is best to think of a monad as an <i>abstract datatype</i>
--   of actions. Haskell's <tt>do</tt> expressions provide a convenient
--   syntax for writing monadic expressions.
--   
--   Instances of <a>Monad</a> should satisfy the following laws:
--   
--   <ul>
--   <li><pre><a>return</a> a <a>&gt;&gt;=</a> k = k a</pre></li>
--   <li><pre>m <a>&gt;&gt;=</a> <a>return</a> = m</pre></li>
--   <li><pre>m <a>&gt;&gt;=</a> (\x -&gt; k x <a>&gt;&gt;=</a> h) = (m
--   <a>&gt;&gt;=</a> k) <a>&gt;&gt;=</a> h</pre></li>
--   </ul>
--   
--   Furthermore, the <a>Monad</a> and <a>Applicative</a> operations should
--   relate as follows:
--   
--   <ul>
--   <li><pre><a>pure</a> = <a>return</a></pre></li>
--   <li><pre>(<a>&lt;*&gt;</a>) = <a>ap</a></pre></li>
--   </ul>
--   
--   The above laws imply:
--   
--   <ul>
--   <li><pre><a>fmap</a> f xs = xs <a>&gt;&gt;=</a> <a>return</a> .
--   f</pre></li>
--   <li><pre>(<a>&gt;&gt;</a>) = (<a>*&gt;</a>)</pre></li>
--   </ul>
--   
--   and that <a>pure</a> and (<a>&lt;*&gt;</a>) satisfy the applicative
--   functor laws.
--   
--   The instances of <a>Monad</a> for lists, <a>Maybe</a> and <a>IO</a>
--   defined in the <a>Prelude</a> satisfy these laws.
class Applicative m => Monad (m :: * -> *)

-- | The class of monoids (types with an associative binary operation that
--   has an identity). Instances should satisfy the following laws:
--   
--   <ul>
--   <li><pre>x <a>&lt;&gt;</a> <a>mempty</a> = x</pre></li>
--   <li><pre><a>mempty</a> <a>&lt;&gt;</a> x = x</pre></li>
--   <li><tt>x <a>&lt;&gt;</a> (y <a>&lt;&gt;</a> z) = (x <a>&lt;&gt;</a>
--   y) <a>&lt;&gt;</a> z</tt> (<a>Semigroup</a> law)</li>
--   <li><pre><a>mconcat</a> = <a>foldr</a> '(&lt;&gt;)'
--   <a>mempty</a></pre></li>
--   </ul>
--   
--   The method names refer to the monoid of lists under concatenation, but
--   there are many other instances.
--   
--   Some types can be viewed as a monoid in more than one way, e.g. both
--   addition and multiplication on numbers. In such cases we often define
--   <tt>newtype</tt>s and make those instances of <a>Monoid</a>, e.g.
--   <tt>Sum</tt> and <tt>Product</tt>.
--   
--   <b>NOTE</b>: <a>Semigroup</a> is a superclass of <a>Monoid</a> since
--   <i>base-4.11.0.0</i>.
class Semigroup a => Monoid a

-- | Basic numeric class.
class Num a

-- | Conversion from an <a>Integer</a>. An integer literal represents the
--   application of the function <a>fromInteger</a> to the appropriate
--   value of type <a>Integer</a>, so such literals have type
--   <tt>(<a>Num</a> a) =&gt; a</tt>.
fromInteger :: Num a => Integer -> a

-- | The <a>Ord</a> class is used for totally ordered datatypes.
--   
--   Instances of <a>Ord</a> can be derived for any user-defined datatype
--   whose constituent types are in <a>Ord</a>. The declared order of the
--   constructors in the data declaration determines the ordering in
--   derived <a>Ord</a> instances. The <a>Ordering</a> datatype allows a
--   single comparison to determine the precise ordering of two objects.
--   
--   Minimal complete definition: either <a>compare</a> or <a>&lt;=</a>.
--   Using <a>compare</a> can be more efficient for complex types.
class Eq a => Ord a

-- | Parsing of <a>String</a>s, producing values.
--   
--   Derived instances of <a>Read</a> make the following assumptions, which
--   derived instances of <a>Show</a> obey:
--   
--   <ul>
--   <li>If the constructor is defined to be an infix operator, then the
--   derived <a>Read</a> instance will parse only infix applications of the
--   constructor (not the prefix form).</li>
--   <li>Associativity is not used to reduce the occurrence of parentheses,
--   although precedence may be.</li>
--   <li>If the constructor is defined using record syntax, the derived
--   <a>Read</a> will parse only the record-syntax form, and furthermore,
--   the fields must be given in the same order as the original
--   declaration.</li>
--   <li>The derived <a>Read</a> instance allows arbitrary Haskell
--   whitespace between tokens of the input string. Extra parentheses are
--   also allowed.</li>
--   </ul>
--   
--   For example, given the declarations
--   
--   <pre>
--   infixr 5 :^:
--   data Tree a =  Leaf a  |  Tree a :^: Tree a
--   </pre>
--   
--   the derived instance of <a>Read</a> in Haskell 2010 is equivalent to
--   
--   <pre>
--   instance (Read a) =&gt; Read (Tree a) where
--   
--           readsPrec d r =  readParen (d &gt; app_prec)
--                            (\r -&gt; [(Leaf m,t) |
--                                    ("Leaf",s) &lt;- lex r,
--                                    (m,t) &lt;- readsPrec (app_prec+1) s]) r
--   
--                         ++ readParen (d &gt; up_prec)
--                            (\r -&gt; [(u:^:v,w) |
--                                    (u,s) &lt;- readsPrec (up_prec+1) r,
--                                    (":^:",t) &lt;- lex s,
--                                    (v,w) &lt;- readsPrec (up_prec+1) t]) r
--   
--             where app_prec = 10
--                   up_prec = 5
--   </pre>
--   
--   Note that right-associativity of <tt>:^:</tt> is unused.
--   
--   The derived instance in GHC is equivalent to
--   
--   <pre>
--   instance (Read a) =&gt; Read (Tree a) where
--   
--           readPrec = parens $ (prec app_prec $ do
--                                    Ident "Leaf" &lt;- lexP
--                                    m &lt;- step readPrec
--                                    return (Leaf m))
--   
--                        +++ (prec up_prec $ do
--                                    u &lt;- step readPrec
--                                    Symbol ":^:" &lt;- lexP
--                                    v &lt;- step readPrec
--                                    return (u :^: v))
--   
--             where app_prec = 10
--                   up_prec = 5
--   
--           readListPrec = readListPrecDefault
--   </pre>
--   
--   Why do both <a>readsPrec</a> and <a>readPrec</a> exist, and why does
--   GHC opt to implement <a>readPrec</a> in derived <a>Read</a> instances
--   instead of <a>readsPrec</a>? The reason is that <a>readsPrec</a> is
--   based on the <a>ReadS</a> type, and although <a>ReadS</a> is mentioned
--   in the Haskell 2010 Report, it is not a very efficient parser data
--   structure.
--   
--   <a>readPrec</a>, on the other hand, is based on a much more efficient
--   <a>ReadPrec</a> datatype (a.k.a "new-style parsers"), but its
--   definition relies on the use of the <tt>RankNTypes</tt> language
--   extension. Therefore, <a>readPrec</a> (and its cousin,
--   <a>readListPrec</a>) are marked as GHC-only. Nevertheless, it is
--   recommended to use <a>readPrec</a> instead of <a>readsPrec</a>
--   whenever possible for the efficiency improvements it brings.
--   
--   As mentioned above, derived <a>Read</a> instances in GHC will
--   implement <a>readPrec</a> instead of <a>readsPrec</a>. The default
--   implementations of <a>readsPrec</a> (and its cousin, <a>readList</a>)
--   will simply use <a>readPrec</a> under the hood. If you are writing a
--   <a>Read</a> instance by hand, it is recommended to write it like so:
--   
--   <pre>
--   instance <a>Read</a> T where
--     <a>readPrec</a>     = ...
--     <a>readListPrec</a> = <a>readListPrecDefault</a>
--   </pre>
class Read a
class (Num a, Ord a) => Real a

-- | Efficient, machine-independent access to the components of a
--   floating-point number.
class (RealFrac a, Floating a) => RealFloat a

-- | Extracting components of fractions.
class (Real a, Fractional a) => RealFrac a

-- | The class of semigroups (types with an associative binary operation).
--   
--   Instances should satisfy the associativity law:
--   
--   <ul>
--   <li><pre>x <a>&lt;&gt;</a> (y <a>&lt;&gt;</a> z) = (x <a>&lt;&gt;</a>
--   y) <a>&lt;&gt;</a> z</pre></li>
--   </ul>
class Semigroup a

-- | Conversion of values to readable <a>String</a>s.
--   
--   Derived instances of <a>Show</a> have the following properties, which
--   are compatible with derived instances of <a>Read</a>:
--   
--   <ul>
--   <li>The result of <a>show</a> is a syntactically correct Haskell
--   expression containing only constants, given the fixity declarations in
--   force at the point where the type is declared. It contains only the
--   constructor names defined in the data type, parentheses, and spaces.
--   When labelled constructor fields are used, braces, commas, field
--   names, and equal signs are also used.</li>
--   <li>If the constructor is defined to be an infix operator, then
--   <a>showsPrec</a> will produce infix applications of the
--   constructor.</li>
--   <li>the representation will be enclosed in parentheses if the
--   precedence of the top-level constructor in <tt>x</tt> is less than
--   <tt>d</tt> (associativity is ignored). Thus, if <tt>d</tt> is
--   <tt>0</tt> then the result is never surrounded in parentheses; if
--   <tt>d</tt> is <tt>11</tt> it is always surrounded in parentheses,
--   unless it is an atomic expression.</li>
--   <li>If the constructor is defined using record syntax, then
--   <a>show</a> will produce the record-syntax form, with the fields given
--   in the same order as the original declaration.</li>
--   </ul>
--   
--   For example, given the declarations
--   
--   <pre>
--   infixr 5 :^:
--   data Tree a =  Leaf a  |  Tree a :^: Tree a
--   </pre>
--   
--   the derived instance of <a>Show</a> is equivalent to
--   
--   <pre>
--   instance (Show a) =&gt; Show (Tree a) where
--   
--          showsPrec d (Leaf m) = showParen (d &gt; app_prec) $
--               showString "Leaf " . showsPrec (app_prec+1) m
--            where app_prec = 10
--   
--          showsPrec d (u :^: v) = showParen (d &gt; up_prec) $
--               showsPrec (up_prec+1) u .
--               showString " :^: "      .
--               showsPrec (up_prec+1) v
--            where up_prec = 5
--   </pre>
--   
--   Note that right-associativity of <tt>:^:</tt> is ignored. For example,
--   
--   <ul>
--   <li><tt><a>show</a> (Leaf 1 :^: Leaf 2 :^: Leaf 3)</tt> produces the
--   string <tt>"Leaf 1 :^: (Leaf 2 :^: Leaf 3)"</tt>.</li>
--   </ul>
class Show a

-- | Functors representing data structures that can be traversed from left
--   to right.
--   
--   A definition of <a>traverse</a> must satisfy the following laws:
--   
--   <ul>
--   <li><i><i>naturality</i></i> <tt>t . <a>traverse</a> f =
--   <a>traverse</a> (t . f)</tt> for every applicative transformation
--   <tt>t</tt></li>
--   <li><i><i>identity</i></i> <tt><a>traverse</a> Identity =
--   Identity</tt></li>
--   <li><i><i>composition</i></i> <tt><a>traverse</a> (Compose .
--   <a>fmap</a> g . f) = Compose . <a>fmap</a> (<a>traverse</a> g) .
--   <a>traverse</a> f</tt></li>
--   </ul>
--   
--   A definition of <a>sequenceA</a> must satisfy the following laws:
--   
--   <ul>
--   <li><i><i>naturality</i></i> <tt>t . <a>sequenceA</a> =
--   <a>sequenceA</a> . <a>fmap</a> t</tt> for every applicative
--   transformation <tt>t</tt></li>
--   <li><i><i>identity</i></i> <tt><a>sequenceA</a> . <a>fmap</a> Identity
--   = Identity</tt></li>
--   <li><i><i>composition</i></i> <tt><a>sequenceA</a> . <a>fmap</a>
--   Compose = Compose . <a>fmap</a> <a>sequenceA</a> .
--   <a>sequenceA</a></tt></li>
--   </ul>
--   
--   where an <i>applicative transformation</i> is a function
--   
--   <pre>
--   t :: (Applicative f, Applicative g) =&gt; f a -&gt; g a
--   </pre>
--   
--   preserving the <a>Applicative</a> operations, i.e.
--   
--   <ul>
--   <li><pre>t (<a>pure</a> x) = <a>pure</a> x</pre></li>
--   <li><pre>t (x <a>&lt;*&gt;</a> y) = t x <a>&lt;*&gt;</a> t
--   y</pre></li>
--   </ul>
--   
--   and the identity functor <tt>Identity</tt> and composition of functors
--   <tt>Compose</tt> are defined as
--   
--   <pre>
--   newtype Identity a = Identity a
--   
--   instance Functor Identity where
--     fmap f (Identity x) = Identity (f x)
--   
--   instance Applicative Identity where
--     pure x = Identity x
--     Identity f &lt;*&gt; Identity x = Identity (f x)
--   
--   newtype Compose f g a = Compose (f (g a))
--   
--   instance (Functor f, Functor g) =&gt; Functor (Compose f g) where
--     fmap f (Compose x) = Compose (fmap (fmap f) x)
--   
--   instance (Applicative f, Applicative g) =&gt; Applicative (Compose f g) where
--     pure x = Compose (pure (pure x))
--     Compose f &lt;*&gt; Compose x = Compose ((&lt;*&gt;) &lt;$&gt; f &lt;*&gt; x)
--   </pre>
--   
--   (The naturality law is implied by parametricity.)
--   
--   Instances are similar to <a>Functor</a>, e.g. given a data type
--   
--   <pre>
--   data Tree a = Empty | Leaf a | Node (Tree a) a (Tree a)
--   </pre>
--   
--   a suitable instance would be
--   
--   <pre>
--   instance Traversable Tree where
--      traverse f Empty = pure Empty
--      traverse f (Leaf x) = Leaf &lt;$&gt; f x
--      traverse f (Node l k r) = Node &lt;$&gt; traverse f l &lt;*&gt; f k &lt;*&gt; traverse f r
--   </pre>
--   
--   This is suitable even for abstract types, as the laws for
--   <a>&lt;*&gt;</a> imply a form of associativity.
--   
--   The superclass instances should satisfy the following:
--   
--   <ul>
--   <li>In the <a>Functor</a> instance, <a>fmap</a> should be equivalent
--   to traversal with the identity applicative functor
--   (<a>fmapDefault</a>).</li>
--   <li>In the <a>Foldable</a> instance, <a>foldMap</a> should be
--   equivalent to traversal with a constant applicative functor
--   (<a>foldMapDefault</a>).</li>
--   </ul>
class (Functor t, Foldable t) => Traversable (t :: * -> *)

-- | A value of type <tt><a>IO</a> a</tt> is a computation which, when
--   performed, does some I/O before returning a value of type <tt>a</tt>.
--   
--   There is really only one way to "perform" an I/O action: bind it to
--   <tt>Main.main</tt> in your program. When your program is run, the I/O
--   will be performed. It isn't possible to perform I/O from an arbitrary
--   function, unless that function is itself in the <a>IO</a> monad and
--   called at some point, directly or indirectly, from <tt>Main.main</tt>.
--   
--   <a>IO</a> is a monad, so <a>IO</a> actions can be combined using
--   either the do-notation or the <tt>&gt;&gt;</tt> and <tt>&gt;&gt;=</tt>
--   operations from the <tt>Monad</tt> class.
data IO a

-- | The character type <a>Char</a> is an enumeration whose values
--   represent Unicode (or equivalently ISO/IEC 10646) code points (i.e.
--   characters, see <a>http://www.unicode.org/</a> for details). This set
--   extends the ISO 8859-1 (Latin-1) character set (the first 256
--   characters), which is itself an extension of the ASCII character set
--   (the first 128 characters). A character literal in Haskell has type
--   <a>Char</a>.
--   
--   To convert a <a>Char</a> to or from the corresponding <a>Int</a> value
--   defined by Unicode, use <a>toEnum</a> and <a>fromEnum</a> from the
--   <a>Enum</a> class respectively (or equivalently <tt>ord</tt> and
--   <tt>chr</tt>).
data Char

-- | Double-precision floating point numbers. It is desirable that this
--   type be at least equal in range and precision to the IEEE
--   double-precision type.
data Double

-- | Single-precision floating point numbers. It is desirable that this
--   type be at least equal in range and precision to the IEEE
--   single-precision type.
data Float

-- | A fixed-precision integer type with at least the range <tt>[-2^29 ..
--   2^29-1]</tt>. The exact range for a given implementation can be
--   determined by using <a>minBound</a> and <a>maxBound</a> from the
--   <a>Bounded</a> class.
data Int

-- | Invariant: <a>Jn#</a> and <a>Jp#</a> are used iff value doesn't fit in
--   <a>S#</a>
--   
--   Useful properties resulting from the invariants:
--   
--   <ul>
--   <li><pre>abs (<a>S#</a> _) &lt;= abs (<a>Jp#</a> _)</pre></li>
--   <li><pre>abs (<a>S#</a> _) &lt; abs (<a>Jn#</a> _)</pre></li>
--   </ul>
data Integer

-- | A <a>Word</a> is an unsigned integral type, with the same size as
--   <a>Int</a>.
data Word
data Bool
False :: Bool
True :: Bool

-- | The <a>Either</a> type represents values with two possibilities: a
--   value of type <tt><a>Either</a> a b</tt> is either <tt><a>Left</a>
--   a</tt> or <tt><a>Right</a> b</tt>.
--   
--   The <a>Either</a> type is sometimes used to represent a value which is
--   either correct or an error; by convention, the <a>Left</a> constructor
--   is used to hold an error value and the <a>Right</a> constructor is
--   used to hold a correct value (mnemonic: "right" also means "correct").
--   
--   <h4><b>Examples</b></h4>
--   
--   The type <tt><a>Either</a> <a>String</a> <a>Int</a></tt> is the type
--   of values which can be either a <a>String</a> or an <a>Int</a>. The
--   <a>Left</a> constructor can be used only on <a>String</a>s, and the
--   <a>Right</a> constructor can be used only on <a>Int</a>s:
--   
--   <pre>
--   &gt;&gt;&gt; let s = Left "foo" :: Either String Int
--   
--   &gt;&gt;&gt; s
--   Left "foo"
--   
--   &gt;&gt;&gt; let n = Right 3 :: Either String Int
--   
--   &gt;&gt;&gt; n
--   Right 3
--   
--   &gt;&gt;&gt; :type s
--   s :: Either String Int
--   
--   &gt;&gt;&gt; :type n
--   n :: Either String Int
--   </pre>
--   
--   The <a>fmap</a> from our <a>Functor</a> instance will ignore
--   <a>Left</a> values, but will apply the supplied function to values
--   contained in a <a>Right</a>:
--   
--   <pre>
--   &gt;&gt;&gt; let s = Left "foo" :: Either String Int
--   
--   &gt;&gt;&gt; let n = Right 3 :: Either String Int
--   
--   &gt;&gt;&gt; fmap (*2) s
--   Left "foo"
--   
--   &gt;&gt;&gt; fmap (*2) n
--   Right 6
--   </pre>
--   
--   The <a>Monad</a> instance for <a>Either</a> allows us to chain
--   together multiple actions which may fail, and fail overall if any of
--   the individual steps failed. First we'll write a function that can
--   either parse an <a>Int</a> from a <a>Char</a>, or fail.
--   
--   <pre>
--   &gt;&gt;&gt; import Data.Char ( digitToInt, isDigit )
--   
--   &gt;&gt;&gt; :{
--       let parseEither :: Char -&gt; Either String Int
--           parseEither c
--             | isDigit c = Right (digitToInt c)
--             | otherwise = Left "parse error"
--   
--   &gt;&gt;&gt; :}
--   </pre>
--   
--   The following should work, since both <tt>'1'</tt> and <tt>'2'</tt>
--   can be parsed as <a>Int</a>s.
--   
--   <pre>
--   &gt;&gt;&gt; :{
--       let parseMultiple :: Either String Int
--           parseMultiple = do
--             x &lt;- parseEither '1'
--             y &lt;- parseEither '2'
--             return (x + y)
--   
--   &gt;&gt;&gt; :}
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; parseMultiple
--   Right 3
--   </pre>
--   
--   But the following should fail overall, since the first operation where
--   we attempt to parse <tt>'m'</tt> as an <a>Int</a> will fail:
--   
--   <pre>
--   &gt;&gt;&gt; :{
--       let parseMultiple :: Either String Int
--           parseMultiple = do
--             x &lt;- parseEither 'm'
--             y &lt;- parseEither '2'
--             return (x + y)
--   
--   &gt;&gt;&gt; :}
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; parseMultiple
--   Left "parse error"
--   </pre>
data Either a b
Left :: a -> Either a b
Right :: b -> Either a b

-- | The <a>Maybe</a> type encapsulates an optional value. A value of type
--   <tt><a>Maybe</a> a</tt> either contains a value of type <tt>a</tt>
--   (represented as <tt><a>Just</a> a</tt>), or it is empty (represented
--   as <a>Nothing</a>). Using <a>Maybe</a> is a good way to deal with
--   errors or exceptional cases without resorting to drastic measures such
--   as <a>error</a>.
--   
--   The <a>Maybe</a> type is also a monad. It is a simple kind of error
--   monad, where all errors are represented by <a>Nothing</a>. A richer
--   error monad can be built using the <a>Either</a> type.
data Maybe a
Nothing :: Maybe a
Just :: a -> Maybe a
data Ordering
LT :: Ordering
EQ :: Ordering
GT :: Ordering

-- | File and directory names are values of type <a>String</a>, whose
--   precise meaning is operating system dependent. Files can be opened,
--   yielding a handle which can then be used to operate on the contents of
--   that file.
type FilePath = String

-- | The Haskell 2010 type for exceptions in the <a>IO</a> monad. Any I/O
--   operation may raise an <a>IOError</a> instead of returning a result.
--   For a more general type of exception, including also those that arise
--   in pure code, see <a>Exception</a>.
--   
--   In Haskell 2010, this is an opaque type.
type IOError = IOException

-- | Arbitrary-precision rational numbers, represented as a ratio of two
--   <a>Integer</a> values. A rational number may be constructed using the
--   <a>%</a> operator.
type Rational = Ratio Integer

-- | A parser for a type <tt>a</tt>, represented as a function that takes a
--   <a>String</a> and returns a list of possible parses as
--   <tt>(a,<a>String</a>)</tt> pairs.
--   
--   Note that this kind of backtracking parser is very inefficient;
--   reading a large structure may be quite slow (cf <a>ReadP</a>).
type ReadS a = String -> [(a, String)]

-- | The <tt>shows</tt> functions return a function that prepends the
--   output <a>String</a> to an existing <a>String</a>. This allows
--   constant-time concatenation of results using function composition.
type ShowS = String -> String

-- | A <a>String</a> is a list of characters. String constants in Haskell
--   are values of type <a>String</a>.
type String = [Char]


-- | Reexports <a>Prelude.Compat</a> from a globally unique namespace.
module Prelude.Compat.Repl


-- | Miscellaneous information about the system environment.
module System.Environment.Compat

-- | Computation <a>getArgs</a> returns a list of the program's command
--   line arguments (not including the program name).
getArgs :: IO [String]

-- | Computation <a>getProgName</a> returns the name of the program as it
--   was invoked.
--   
--   However, this is hard-to-impossible to implement on some non-Unix
--   OSes, so instead, for maximum portability, we just return the leafname
--   of the program as invoked. Even then there are some differences
--   between platforms: on Windows, for example, a program invoked as foo
--   is probably really <tt>FOO.EXE</tt>, and that is what
--   <a>getProgName</a> will return.
getProgName :: IO String

-- | Computation <a>getEnv</a> <tt>var</tt> returns the value of the
--   environment variable <tt>var</tt>. For the inverse, the <a>setEnv</a>
--   function can be used.
--   
--   This computation may fail with:
--   
--   <ul>
--   <li><a>isDoesNotExistError</a> if the environment variable does not
--   exist.</li>
--   </ul>
getEnv :: String -> IO String

-- | Return the value of the environment variable <tt>var</tt>, or
--   <tt>Nothing</tt> if there is no such value.
--   
--   For POSIX users, this is equivalent to <a>getEnv</a>.
lookupEnv :: String -> IO Maybe String

-- | <tt>setEnv name value</tt> sets the specified environment variable to
--   <tt>value</tt>.
--   
--   Early versions of this function operated under the mistaken belief
--   that setting an environment variable to the <i>empty string</i> on
--   Windows removes that environment variable from the environment. For
--   the sake of compatibility, it adopted that behavior on POSIX. In
--   particular
--   
--   <pre>
--   setEnv name ""
--   </pre>
--   
--   has the same effect as
--   
--   <pre>
--   <a>unsetEnv</a> name
--   </pre>
--   
--   If you'd like to be able to set environment variables to blank
--   strings, use <a>setEnv</a>.
--   
--   Throws <a>IOException</a> if <tt>name</tt> is the empty string or
--   contains an equals sign.
setEnv :: String -> String -> IO ()

-- | <tt>unsetEnv name</tt> removes the specified environment variable from
--   the environment of the current process.
--   
--   Throws <a>IOException</a> if <tt>name</tt> is the empty string or
--   contains an equals sign.
unsetEnv :: String -> IO ()

-- | <a>withArgs</a> <tt>args act</tt> - while executing action
--   <tt>act</tt>, have <a>getArgs</a> return <tt>args</tt>.
withArgs :: () => [String] -> IO a -> IO a

-- | <a>withProgName</a> <tt>name act</tt> - while executing action
--   <tt>act</tt>, have <a>getProgName</a> return <tt>name</tt>.
withProgName :: () => String -> IO a -> IO a

-- | <a>getEnvironment</a> retrieves the entire environment as a list of
--   <tt>(key,value)</tt> pairs.
--   
--   If an environment entry does not contain an <tt>'='</tt> character,
--   the <tt>key</tt> is the whole entry and the <tt>value</tt> is the
--   empty string.
getEnvironment :: IO [(String, String)]


-- | Reexports <a>System.Environment.Compat</a> from a globally unique
--   namespace.
module System.Environment.Compat.Repl

module System.Exit.Compat

-- | Write given error message to <a>stderr</a> and terminate with
--   <a>exitFailure</a>.
die :: () => String -> IO a


-- | Reexports <a>System.Exit.Compat</a> from a globally unique namespace.
module System.Exit.Compat.Repl

module System.IO.Unsafe.Compat

-- | A slightly faster version of <a>fixIO</a> that may not be safe to use
--   with multiple threads. The unsafety arises when used like this:
--   
--   <pre>
--   unsafeFixIO $ \r -&gt; do
--      forkIO (print r)
--      return (...)
--   </pre>
--   
--   In this case, the child thread will receive a <tt>NonTermination</tt>
--   exception instead of waiting for the value of <tt>r</tt> to be
--   computed.
unsafeFixIO :: () => a -> IO a -> IO a

-- | This version of <a>unsafePerformIO</a> is more efficient because it
--   omits the check that the IO is only being performed by a single
--   thread. Hence, when you use <a>unsafeDupablePerformIO</a>, there is a
--   possibility that the IO action may be performed multiple times (on a
--   multiprocessor), and you should therefore ensure that it gives the
--   same results each time. It may even happen that one of the duplicated
--   IO actions is only run partially, and then interrupted in the middle
--   without an exception being raised. Therefore, functions like
--   <tt>bracket</tt> cannot be used safely within
--   <a>unsafeDupablePerformIO</a>.
unsafeDupablePerformIO :: () => IO a -> a


-- | Reexports <a>System.IO.Unsafe.Compat</a> from a globally unique
--   namespace.
module System.IO.Unsafe.Compat.Repl

module Text.Read.Compat

-- | Parsing of <a>String</a>s, producing values.
--   
--   Derived instances of <a>Read</a> make the following assumptions, which
--   derived instances of <a>Show</a> obey:
--   
--   <ul>
--   <li>If the constructor is defined to be an infix operator, then the
--   derived <a>Read</a> instance will parse only infix applications of the
--   constructor (not the prefix form).</li>
--   <li>Associativity is not used to reduce the occurrence of parentheses,
--   although precedence may be.</li>
--   <li>If the constructor is defined using record syntax, the derived
--   <a>Read</a> will parse only the record-syntax form, and furthermore,
--   the fields must be given in the same order as the original
--   declaration.</li>
--   <li>The derived <a>Read</a> instance allows arbitrary Haskell
--   whitespace between tokens of the input string. Extra parentheses are
--   also allowed.</li>
--   </ul>
--   
--   For example, given the declarations
--   
--   <pre>
--   infixr 5 :^:
--   data Tree a =  Leaf a  |  Tree a :^: Tree a
--   </pre>
--   
--   the derived instance of <a>Read</a> in Haskell 2010 is equivalent to
--   
--   <pre>
--   instance (Read a) =&gt; Read (Tree a) where
--   
--           readsPrec d r =  readParen (d &gt; app_prec)
--                            (\r -&gt; [(Leaf m,t) |
--                                    ("Leaf",s) &lt;- lex r,
--                                    (m,t) &lt;- readsPrec (app_prec+1) s]) r
--   
--                         ++ readParen (d &gt; up_prec)
--                            (\r -&gt; [(u:^:v,w) |
--                                    (u,s) &lt;- readsPrec (up_prec+1) r,
--                                    (":^:",t) &lt;- lex s,
--                                    (v,w) &lt;- readsPrec (up_prec+1) t]) r
--   
--             where app_prec = 10
--                   up_prec = 5
--   </pre>
--   
--   Note that right-associativity of <tt>:^:</tt> is unused.
--   
--   The derived instance in GHC is equivalent to
--   
--   <pre>
--   instance (Read a) =&gt; Read (Tree a) where
--   
--           readPrec = parens $ (prec app_prec $ do
--                                    Ident "Leaf" &lt;- lexP
--                                    m &lt;- step readPrec
--                                    return (Leaf m))
--   
--                        +++ (prec up_prec $ do
--                                    u &lt;- step readPrec
--                                    Symbol ":^:" &lt;- lexP
--                                    v &lt;- step readPrec
--                                    return (u :^: v))
--   
--             where app_prec = 10
--                   up_prec = 5
--   
--           readListPrec = readListPrecDefault
--   </pre>
--   
--   Why do both <a>readsPrec</a> and <a>readPrec</a> exist, and why does
--   GHC opt to implement <a>readPrec</a> in derived <a>Read</a> instances
--   instead of <a>readsPrec</a>? The reason is that <a>readsPrec</a> is
--   based on the <a>ReadS</a> type, and although <a>ReadS</a> is mentioned
--   in the Haskell 2010 Report, it is not a very efficient parser data
--   structure.
--   
--   <a>readPrec</a>, on the other hand, is based on a much more efficient
--   <a>ReadPrec</a> datatype (a.k.a "new-style parsers"), but its
--   definition relies on the use of the <tt>RankNTypes</tt> language
--   extension. Therefore, <a>readPrec</a> (and its cousin,
--   <a>readListPrec</a>) are marked as GHC-only. Nevertheless, it is
--   recommended to use <a>readPrec</a> instead of <a>readsPrec</a>
--   whenever possible for the efficiency improvements it brings.
--   
--   As mentioned above, derived <a>Read</a> instances in GHC will
--   implement <a>readPrec</a> instead of <a>readsPrec</a>. The default
--   implementations of <a>readsPrec</a> (and its cousin, <a>readList</a>)
--   will simply use <a>readPrec</a> under the hood. If you are writing a
--   <a>Read</a> instance by hand, it is recommended to write it like so:
--   
--   <pre>
--   instance <a>Read</a> T where
--     <a>readPrec</a>     = ...
--     <a>readListPrec</a> = <a>readListPrecDefault</a>
--   </pre>
class Read a

-- | attempts to parse a value from the front of the string, returning a
--   list of (parsed value, remaining string) pairs. If there is no
--   successful parse, the returned list is empty.
--   
--   Derived instances of <a>Read</a> and <a>Show</a> satisfy the
--   following:
--   
--   <ul>
--   <li><tt>(x,"")</tt> is an element of <tt>(<a>readsPrec</a> d
--   (<a>showsPrec</a> d x ""))</tt>.</li>
--   </ul>
--   
--   That is, <a>readsPrec</a> parses the string produced by
--   <a>showsPrec</a>, and delivers the value that <a>showsPrec</a> started
--   with.
readsPrec :: Read a => Int -> ReadS a

-- | The method <a>readList</a> is provided to allow the programmer to give
--   a specialised way of parsing lists of values. For example, this is
--   used by the predefined <a>Read</a> instance of the <a>Char</a> type,
--   where values of type <a>String</a> should be are expected to use
--   double quotes, rather than square brackets.
readList :: Read a => ReadS [a]

-- | Proposed replacement for <a>readsPrec</a> using new-style parsers (GHC
--   only).
readPrec :: Read a => ReadPrec a

-- | Proposed replacement for <a>readList</a> using new-style parsers (GHC
--   only). The default definition uses <a>readList</a>. Instances that
--   define <a>readPrec</a> should also define <a>readListPrec</a> as
--   <a>readListPrecDefault</a>.
readListPrec :: Read a => ReadPrec [a]

-- | A parser for a type <tt>a</tt>, represented as a function that takes a
--   <a>String</a> and returns a list of possible parses as
--   <tt>(a,<a>String</a>)</tt> pairs.
--   
--   Note that this kind of backtracking parser is very inefficient;
--   reading a large structure may be quite slow (cf <a>ReadP</a>).
type ReadS a = String -> [(a, String)]

-- | equivalent to <a>readsPrec</a> with a precedence of 0.
reads :: Read a => ReadS a

-- | The <a>read</a> function reads input from a string, which must be
--   completely consumed by the input process. <a>read</a> fails with an
--   <a>error</a> if the parse is unsuccessful, and it is therefore
--   discouraged from being used in real applications. Use <a>readMaybe</a>
--   or <a>readEither</a> for safe alternatives.
--   
--   <pre>
--   &gt;&gt;&gt; read "123" :: Int
--   123
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; read "hello" :: Int
--   *** Exception: Prelude.read: no parse
--   </pre>
read :: Read a => String -> a

-- | <tt><a>readParen</a> <a>True</a> p</tt> parses what <tt>p</tt> parses,
--   but surrounded with parentheses.
--   
--   <tt><a>readParen</a> <a>False</a> p</tt> parses what <tt>p</tt>
--   parses, but optionally surrounded with parentheses.
readParen :: () => Bool -> ReadS a -> ReadS a

-- | The <a>lex</a> function reads a single lexeme from the input,
--   discarding initial white space, and returning the characters that
--   constitute the lexeme. If the input string contains only white space,
--   <a>lex</a> returns a single successful `lexeme' consisting of the
--   empty string. (Thus <tt><a>lex</a> "" = [("","")]</tt>.) If there is
--   no legal lexeme at the beginning of the input string, <a>lex</a> fails
--   (i.e. returns <tt>[]</tt>).
--   
--   This lexer is not completely faithful to the Haskell lexical syntax in
--   the following respects:
--   
--   <ul>
--   <li>Qualified names are not handled properly</li>
--   <li>Octal and hexadecimal numerics are not recognized as a single
--   token</li>
--   <li>Comments are not treated properly</li>
--   </ul>
lex :: ReadS String
data Lexeme

-- | Character literal
Char :: Char -> Lexeme

-- | String literal, with escapes interpreted
String :: String -> Lexeme

-- | Punctuation or reserved symbol, e.g. <tt>(</tt>, <tt>::</tt>
Punc :: String -> Lexeme

-- | Haskell identifier, e.g. <tt>foo</tt>, <tt>Baz</tt>
Ident :: String -> Lexeme

-- | Haskell symbol, e.g. <tt>&gt;&gt;</tt>, <tt>:%</tt>
Symbol :: String -> Lexeme

Number :: Number -> Lexeme
EOF :: Lexeme

-- | Parse a single lexeme
lexP :: ReadPrec Lexeme

-- | <tt>(parens p)</tt> parses "P", "(P0)", "((P0))", etc, where
--   <tt>p</tt> parses "P" in the current precedence context and parses
--   "P0" in precedence context zero
parens :: () => ReadPrec a -> ReadPrec a

-- | A possible replacement definition for the <a>readList</a> method (GHC
--   only). This is only needed for GHC, and even then only for <a>Read</a>
--   instances where <a>readListPrec</a> isn't defined as
--   <a>readListPrecDefault</a>.
readListDefault :: Read a => ReadS [a]

-- | A possible replacement definition for the <a>readListPrec</a> method,
--   defined using <a>readPrec</a> (GHC only).
readListPrecDefault :: Read a => ReadPrec [a]

-- | Parse a string using the <a>Read</a> instance. Succeeds if there is
--   exactly one valid result. A <a>Left</a> value indicates a parse error.
--   
--   <pre>
--   &gt;&gt;&gt; readEither "123" :: Either String Int
--   Right 123
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; readEither "hello" :: Either String Int
--   Left "Prelude.read: no parse"
--   </pre>
readEither :: Read a => String -> Either String a

-- | Parse a string using the <a>Read</a> instance. Succeeds if there is
--   exactly one valid result.
--   
--   <pre>
--   &gt;&gt;&gt; readMaybe "123" :: Maybe Int
--   Just 123
--   </pre>
--   
--   <pre>
--   &gt;&gt;&gt; readMaybe "hello" :: Maybe Int
--   Nothing
--   </pre>
readMaybe :: Read a => String -> Maybe a


-- | Reexports <a>Text.Read.Compat</a> from a globally unique namespace.
module Text.Read.Compat.Repl

module Type.Reflection.Compat

-- | Use a <a>TypeRep</a> as <a>Typeable</a> evidence.
withTypeable :: () => TypeRep a -> Typeable a -> r -> r


-- | Reexports <a>Type.Reflection.Compat</a> from a globally unique
--   namespace.
module Type.Reflection.Compat.Repl
