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|
{-# LANGUAGE Unsafe #-}
{-# LANGUAGE MagicHash, UnboxedTuples, DeriveDataTypeable, TypeFamilies, MultiParamTypeClasses, FlexibleInstances #-}
-----------------------------------------------------------------------------
-- |
-- Module : GHC.Exts
-- Copyright : (c) The University of Glasgow 2002
-- License : see libraries/base/LICENSE
--
-- Maintainer : cvs-ghc@haskell.org
-- Stability : internal
-- Portability : non-portable (GHC Extensions)
--
-- GHC Extensions: this is the Approved Way to get at GHC-specific extensions.
--
-- Note: no other base module should import this module.
-----------------------------------------------------------------------------
module GHC.Exts
(
-- * Representations of some basic types
Int(..),Word(..),Float(..),Double(..),
Char(..),
Ptr(..), FunPtr(..),
-- * The maximum tuple size
maxTupleSize,
-- * Primitive operations
module GHC.Prim,
shiftL#, shiftRL#, iShiftL#, iShiftRA#, iShiftRL#,
uncheckedShiftL64#, uncheckedShiftRL64#,
uncheckedIShiftL64#, uncheckedIShiftRA64#,
isTrue#,
-- * Fusion
build, augment,
-- * Overloaded string literals
IsString(..),
-- * Debugging
breakpoint, breakpointCond,
-- * Ids with special behaviour
lazy, inline,
-- * Transform comprehensions
Down(..), groupWith, sortWith, the,
-- * Event logging
traceEvent,
-- * SpecConstr annotations
SpecConstrAnnotation(..),
-- * The call stack
currentCallStack,
-- * The Constraint kind
Constraint,
-- * Overloaded lists
IsList(..)
) where
import Prelude
import GHC.Prim
import GHC.Base
import GHC.Word
import GHC.Int
import GHC.Ptr
import GHC.Stack
import Data.String
import Data.List
import Data.Data
import Data.Ord
import qualified Debug.Trace
-- XXX This should really be in Data.Tuple, where the definitions are
maxTupleSize :: Int
maxTupleSize = 62
-- | 'the' ensures that all the elements of the list are identical
-- and then returns that unique element
the :: Eq a => [a] -> a
the (x:xs)
| all (x ==) xs = x
| otherwise = error "GHC.Exts.the: non-identical elements"
the [] = error "GHC.Exts.the: empty list"
-- | The 'sortWith' function sorts a list of elements using the
-- user supplied function to project something out of each element
sortWith :: Ord b => (a -> b) -> [a] -> [a]
sortWith f = sortBy (\x y -> compare (f x) (f y))
-- | The 'groupWith' function uses the user supplied function which
-- projects an element out of every list element in order to first sort the
-- input list and then to form groups by equality on these projected elements
{-# INLINE groupWith #-}
groupWith :: Ord b => (a -> b) -> [a] -> [[a]]
groupWith f xs = build (\c n -> groupByFB c n (\x y -> f x == f y) (sortWith f xs))
groupByFB :: ([a] -> lst -> lst) -> lst -> (a -> a -> Bool) -> [a] -> lst
groupByFB c n eq xs0 = groupByFBCore xs0
where groupByFBCore [] = n
groupByFBCore (x:xs) = c (x:ys) (groupByFBCore zs)
where (ys, zs) = span (eq x) xs
-- -----------------------------------------------------------------------------
-- tracing
traceEvent :: String -> IO ()
traceEvent = Debug.Trace.traceEventIO
{-# DEPRECATED traceEvent "Use Debug.Trace.traceEvent or Debug.Trace.traceEventIO" #-} -- deprecated in 7.4
{- **********************************************************************
* *
* SpecConstr annotation *
* *
********************************************************************** -}
-- Annotating a type with NoSpecConstr will make SpecConstr
-- not specialise for arguments of that type.
-- This data type is defined here, rather than in the SpecConstr module
-- itself, so that importing it doesn't force stupidly linking the
-- entire ghc package at runtime
data SpecConstrAnnotation = NoSpecConstr | ForceSpecConstr
deriving( Data, Typeable, Eq )
{- **********************************************************************
* *
* The IsList class *
* *
********************************************************************** -}
-- | The 'IsList' class and its methods are intended to be used in
-- conjunction with the OverloadedLists extension.
--
-- /Since: 4.7.0.0/
class IsList l where
-- | The 'Item' type function returns the type of items of the structure
-- @l@.
type Item l
-- | The 'fromList' function constructs the structure @l@ from the given
-- list of @Item l@
fromList :: [Item l] -> l
-- | The 'fromListN' function takes the input list's length as a hint. Its
-- behaviour should be equivalent to 'fromList'. The hint can be used to
-- construct the structure @l@ more efficiently compared to 'fromList'. If
-- the given hint does not equal to the input list's length the behaviour of
-- 'fromListN' is not specified.
fromListN :: Int -> [Item l] -> l
fromListN _ = fromList
-- | The 'toList' function extracts a list of @Item l@ from the structure @l@.
-- It should satisfy fromList . toList = id.
toList :: l -> [Item l]
instance IsList [a] where
type (Item [a]) = a
fromList = id
toList = id
|
