1 \section[GHC.Base]{Module @GHC.Base@}
3 The overall structure of the GHC Prelude is a bit tricky.
5 a) We want to avoid "orphan modules", i.e. ones with instance
6 decls that don't belong either to a tycon or a class
7 defined in the same module
9 b) We want to avoid giant modules
11 So the rough structure is as follows, in (linearised) dependency order
14 GHC.Prim Has no implementation. It defines built-in things, and
15 by importing it you bring them into scope.
16 The source file is GHC.Prim.hi-boot, which is just
17 copied to make GHC.Prim.hi
19 GHC.Base Classes: Eq, Ord, Functor, Monad
20 Types: list, (), Int, Bool, Ordering, Char, String
22 Data.Tup Types: tuples, plus instances for GHC.Base classes
24 GHC.Show Class: Show, plus instances for GHC.Base/GHC.Tup types
26 GHC.Enum Class: Enum, plus instances for GHC.Base/GHC.Tup types
28 Data.Maybe Type: Maybe, plus instances for GHC.Base classes
30 GHC.Num Class: Num, plus instances for Int
31 Type: Integer, plus instances for all classes so far (Eq, Ord, Num, Show)
33 Integer is needed here because it is mentioned in the signature
34 of 'fromInteger' in class Num
36 GHC.Real Classes: Real, Integral, Fractional, RealFrac
37 plus instances for Int, Integer
38 Types: Ratio, Rational
39 plus intances for classes so far
41 Rational is needed here because it is mentioned in the signature
42 of 'toRational' in class Real
44 Ix Classes: Ix, plus instances for Int, Bool, Char, Integer, Ordering, tuples
46 GHC.Arr Types: Array, MutableArray, MutableVar
48 Does *not* contain any ByteArray stuff (see GHC.ByteArr)
49 Arrays are used by a function in GHC.Float
51 GHC.Float Classes: Floating, RealFloat
52 Types: Float, Double, plus instances of all classes so far
54 This module contains everything to do with floating point.
55 It is a big module (900 lines)
56 With a bit of luck, many modules can be compiled without ever reading GHC.Float.hi
58 GHC.ByteArr Types: ByteArray, MutableByteArray
60 We want this one to be after GHC.Float, because it defines arrays
64 Other Prelude modules are much easier with fewer complex dependencies.
67 {-# OPTIONS -fno-implicit-prelude #-}
68 -----------------------------------------------------------------------------
71 -- Copyright : (c) The University of Glasgow, 1992-2002
72 -- License : see libraries/base/LICENSE
74 -- Maintainer : cvs-ghc@haskell.org
75 -- Stability : internal
76 -- Portability : non-portable (GHC extensions)
78 -- Basic data types and classes.
80 -----------------------------------------------------------------------------
87 module GHC.Prim, -- Re-export GHC.Prim and GHC.Err, to avoid lots
88 module GHC.Err -- of people having to import it explicitly
93 import {-# SOURCE #-} GHC.Err
97 infix 4 ==, /=, <, <=, >=, >
103 default () -- Double isn't available yet
107 %*********************************************************
109 \subsection{DEBUGGING STUFF}
110 %* (for use when compiling GHC.Base itself doesn't work)
112 %*********************************************************
116 data Bool = False | True
117 data Ordering = LT | EQ | GT
125 (&&) True True = True
131 unpackCString# :: Addr# -> [Char]
132 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
133 unpackAppendCString# :: Addr# -> [Char] -> [Char]
134 unpackCStringUtf8# :: Addr# -> [Char]
135 unpackCString# a = error "urk"
136 unpackFoldrCString# a = error "urk"
137 unpackAppendCString# a = error "urk"
138 unpackCStringUtf8# a = error "urk"
143 %*********************************************************
145 \subsection{Standard classes @Eq@, @Ord@}
147 %*********************************************************
151 -- | The 'Eq' class defines equality ('==') and inequality ('/=').
152 -- All the basic datatypes exported by the "Prelude" are instances of 'Eq',
153 -- and 'Eq' may be derived for any datatype whose constituents are also
154 -- instances of 'Eq'.
156 -- Minimal complete definition: either '==' or '/='.
159 (==), (/=) :: a -> a -> Bool
161 x /= y = not (x == y)
162 x == y = not (x /= y)
164 class (Eq a) => Ord a where
165 compare :: a -> a -> Ordering
166 (<), (<=), (>), (>=) :: a -> a -> Bool
167 max, min :: a -> a -> a
169 -- An instance of Ord should define either 'compare' or '<='.
170 -- Using 'compare' can be more efficient for complex types.
174 | x <= y = LT -- NB: must be '<=' not '<' to validate the
175 -- above claim about the minimal things that
176 -- can be defined for an instance of Ord
179 x < y = case compare x y of { LT -> True; _other -> False }
180 x <= y = case compare x y of { GT -> False; _other -> True }
181 x > y = case compare x y of { GT -> True; _other -> False }
182 x >= y = case compare x y of { LT -> False; _other -> True }
184 -- These two default methods use '<=' rather than 'compare'
185 -- because the latter is often more expensive
186 max x y = if x <= y then y else x
187 min x y = if x <= y then x else y
190 %*********************************************************
192 \subsection{Monadic classes @Functor@, @Monad@ }
194 %*********************************************************
197 {- | The 'Functor' class is used for types that can be mapped over.
198 Instances of 'Functor' should satisfy the following laws:
201 > fmap (f . g) == fmap f . fmap g
203 The instances of 'Functor' for lists, 'Maybe' and 'IO' defined in the "Prelude"
207 class Functor f where
208 fmap :: (a -> b) -> f a -> f b
210 {- | The 'Monad' class defines the basic operations over a /monad/.
211 Instances of 'Monad' should satisfy the following laws:
213 > return a >>= k == k a
215 > m >>= (\x -> k x >>= h) == (m >>= k) >>= h
217 Instances of both 'Monad' and 'Functor' should additionally satisfy the law:
219 > fmap f xs == xs >>= return . f
221 The instances of 'Monad' for lists, 'Maybe' and 'IO' defined in the "Prelude"
226 (>>=) :: forall a b. m a -> (a -> m b) -> m b
227 (>>) :: forall a b. m a -> m b -> m b
228 -- Explicit for-alls so that we know what order to
229 -- give type arguments when desugaring
231 fail :: String -> m a
233 m >> k = m >>= \_ -> k
238 %*********************************************************
240 \subsection{The list type}
242 %*********************************************************
245 data [] a = [] | a : [a] -- do explicitly: deriving (Eq, Ord)
246 -- to avoid weird names like con2tag_[]#
249 instance (Eq a) => Eq [a] where
250 {-# SPECIALISE instance Eq [Char] #-}
252 (x:xs) == (y:ys) = x == y && xs == ys
255 instance (Ord a) => Ord [a] where
256 {-# SPECIALISE instance Ord [Char] #-}
258 compare [] (_:_) = LT
259 compare (_:_) [] = GT
260 compare (x:xs) (y:ys) = case compare x y of
264 instance Functor [] where
267 instance Monad [] where
268 m >>= k = foldr ((++) . k) [] m
269 m >> k = foldr ((++) . (\ _ -> k)) [] m
274 A few list functions that appear here because they are used here.
275 The rest of the prelude list functions are in GHC.List.
277 ----------------------------------------------
278 -- foldr/build/augment
279 ----------------------------------------------
282 -- | 'foldr', applied to a binary operator, a starting value (typically
283 -- the right-identity of the operator), and a list, reduces the list
284 -- using the binary operator, from right to left:
286 -- > foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
288 foldr :: (a -> b -> b) -> b -> [a] -> b
290 -- foldr f z (x:xs) = f x (foldr f z xs)
291 {-# INLINE [0] foldr #-}
292 -- Inline only in the final stage, after the foldr/cons rule has had a chance
296 go (y:ys) = y `k` go ys
298 build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
299 {-# INLINE [1] build #-}
300 -- The INLINE is important, even though build is tiny,
301 -- because it prevents [] getting inlined in the version that
302 -- appears in the interface file. If [] *is* inlined, it
303 -- won't match with [] appearing in rules in an importing module.
305 -- The "1" says to inline in phase 1
309 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
310 {-# INLINE [1] augment #-}
311 augment g xs = g (:) xs
314 "fold/build" forall k z (g::forall b. (a->b->b) -> b -> b) .
315 foldr k z (build g) = g k z
317 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) .
318 foldr k z (augment g xs) = g k (foldr k z xs)
320 "foldr/id" foldr (:) [] = \x->x
321 "foldr/app" [1] forall xs ys. foldr (:) ys xs = xs ++ ys
322 -- Only activate this from phase 1, because that's
323 -- when we disable the rule that expands (++) into foldr
325 -- The foldr/cons rule looks nice, but it can give disastrously
326 -- bloated code when commpiling
327 -- array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]
328 -- i.e. when there are very very long literal lists
329 -- So I've disabled it for now. We could have special cases
330 -- for short lists, I suppose.
331 -- "foldr/cons" forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)
333 "foldr/single" forall k z x. foldr k z [x] = k x z
334 "foldr/nil" forall k z. foldr k z [] = z
336 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)
337 (h::forall b. (a->b->b) -> b -> b) .
338 augment g (build h) = build (\c n -> g c (h c n))
339 "augment/nil" forall (g::forall b. (a->b->b) -> b -> b) .
340 augment g [] = build g
343 -- This rule is true, but not (I think) useful:
344 -- augment g (augment h t) = augment (\cn -> g c (h c n)) t
348 ----------------------------------------------
350 ----------------------------------------------
353 -- | 'map' @f xs@ is the list obtained by applying @f@ to each element
356 -- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
357 -- > map f [x1, x2, ...] == [f x1, f x2, ...]
359 map :: (a -> b) -> [a] -> [b]
361 map f (x:xs) = f x : map f xs
364 mapFB :: (elt -> lst -> lst) -> (a -> elt) -> a -> lst -> lst
365 {-# INLINE [0] mapFB #-}
366 mapFB c f x ys = c (f x) ys
368 -- The rules for map work like this.
370 -- Up to (but not including) phase 1, we use the "map" rule to
371 -- rewrite all saturated applications of map with its build/fold
372 -- form, hoping for fusion to happen.
373 -- In phase 1 and 0, we switch off that rule, inline build, and
374 -- switch on the "mapList" rule, which rewrites the foldr/mapFB
375 -- thing back into plain map.
377 -- It's important that these two rules aren't both active at once
378 -- (along with build's unfolding) else we'd get an infinite loop
379 -- in the rules. Hence the activation control below.
381 -- The "mapFB" rule optimises compositions of map.
383 -- This same pattern is followed by many other functions:
384 -- e.g. append, filter, iterate, repeat, etc.
387 "map" [~1] forall f xs. map f xs = build (\c n -> foldr (mapFB c f) n xs)
388 "mapList" [1] forall f. foldr (mapFB (:) f) [] = map f
389 "mapFB" forall c f g. mapFB (mapFB c f) g = mapFB c (f.g)
394 ----------------------------------------------
396 ----------------------------------------------
398 -- | Append two lists, i.e.,
400 -- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
401 -- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
403 -- If the first list is not finite, the result is the first list.
405 (++) :: [a] -> [a] -> [a]
407 (++) (x:xs) ys = x : xs ++ ys
410 "++" [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys
416 %*********************************************************
418 \subsection{Type @Bool@}
420 %*********************************************************
423 -- |The 'Bool' type is an enumeration. It is defined with 'False'
424 -- first so that the corresponding 'Prelude.Enum' instance will give
425 -- 'Prelude.fromEnum' 'False' the value zero, and
426 -- 'Prelude.fromEnum' 'True' the value 1.
427 data Bool = False | True deriving (Eq, Ord)
428 -- Read in GHC.Read, Show in GHC.Show
433 (&&) :: Bool -> Bool -> Bool
438 (||) :: Bool -> Bool -> Bool
447 -- |'otherwise' is defined as the value 'True'. It helps to make
448 -- guards more readable. eg.
450 -- > f x | x < 0 = ...
451 -- > | otherwise = ...
457 %*********************************************************
459 \subsection{The @()@ type}
461 %*********************************************************
463 The Unit type is here because virtually any program needs it (whereas
464 some programs may get away without consulting GHC.Tup). Furthermore,
465 the renamer currently *always* asks for () to be in scope, so that
466 ccalls can use () as their default type; so when compiling GHC.Base we
467 need (). (We could arrange suck in () only if -fglasgow-exts, but putting
468 it here seems more direct.)
471 -- | The unit datatype @()@ has one non-undefined member, the nullary
479 instance Ord () where
490 %*********************************************************
492 \subsection{Type @Ordering@}
494 %*********************************************************
497 -- | Represents an ordering relationship between two values: less
498 -- than, equal to, or greater than. An 'Ordering' is returned by
500 data Ordering = LT | EQ | GT deriving (Eq, Ord)
501 -- Read in GHC.Read, Show in GHC.Show
505 %*********************************************************
507 \subsection{Type @Char@ and @String@}
509 %*********************************************************
512 -- | A 'String' is a list of characters. String constants in Haskell are values
517 {-| The character type 'Char' is an enumeration whose values represent
518 Unicode (or equivalently ISO 10646) characters.
519 This set extends the ISO 8859-1 (Latin-1) character set
520 (the first 256 charachers), which is itself an extension of the ASCII
521 character set (the first 128 characters).
522 A character literal in Haskell has type 'Char'.
524 To convert a 'Char' to or from the corresponding 'Int' value defined
525 by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
526 'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
530 -- We don't use deriving for Eq and Ord, because for Ord the derived
531 -- instance defines only compare, which takes two primops. Then
532 -- '>' uses compare, and therefore takes two primops instead of one.
534 instance Eq Char where
535 (C# c1) == (C# c2) = c1 `eqChar#` c2
536 (C# c1) /= (C# c2) = c1 `neChar#` c2
538 instance Ord Char where
539 (C# c1) > (C# c2) = c1 `gtChar#` c2
540 (C# c1) >= (C# c2) = c1 `geChar#` c2
541 (C# c1) <= (C# c2) = c1 `leChar#` c2
542 (C# c1) < (C# c2) = c1 `ltChar#` c2
545 "x# `eqChar#` x#" forall x#. x# `eqChar#` x# = True
546 "x# `neChar#` x#" forall x#. x# `neChar#` x# = False
547 "x# `gtChar#` x#" forall x#. x# `gtChar#` x# = False
548 "x# `geChar#` x#" forall x#. x# `geChar#` x# = True
549 "x# `leChar#` x#" forall x#. x# `leChar#` x# = True
550 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
553 -- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
555 chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
556 | otherwise = error "Prelude.chr: bad argument"
558 unsafeChr :: Int -> Char
559 unsafeChr (I# i#) = C# (chr# i#)
561 -- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
563 ord (C# c#) = I# (ord# c#)
566 String equality is used when desugaring pattern-matches against strings.
569 eqString :: String -> String -> Bool
570 eqString [] [] = True
571 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
572 eqString cs1 cs2 = False
574 {-# RULES "eqString" (==) = eqString #-}
578 %*********************************************************
580 \subsection{Type @Int@}
582 %*********************************************************
586 -- ^A fixed-precision integer type with at least the range @[-2^29
587 -- .. 2^29-1]@. The exact range for a given implementation can be
588 -- determined by using 'minBound' and 'maxBound' from the 'Bounded'
591 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
596 {- Seems clumsy. Should perhaps put minInt and MaxInt directly into MachDeps.h -}
597 #if WORD_SIZE_IN_BITS == 31
598 minInt = I# (-0x40000000#)
599 maxInt = I# 0x3FFFFFFF#
600 #elif WORD_SIZE_IN_BITS == 32
601 minInt = I# (-0x80000000#)
602 maxInt = I# 0x7FFFFFFF#
604 minInt = I# (-0x8000000000000000#)
605 maxInt = I# 0x7FFFFFFFFFFFFFFF#
608 instance Eq Int where
612 instance Ord Int where
619 compareInt :: Int -> Int -> Ordering
620 (I# x#) `compareInt` (I# y#) = compareInt# x# y#
622 compareInt# :: Int# -> Int# -> Ordering
630 %*********************************************************
632 \subsection{The function type}
634 %*********************************************************
641 -- lazy function; this is just the same as id, but its unfolding
642 -- and strictness are over-ridden by the definition in MkId.lhs
643 -- That way, it does not get inlined, and the strictness analyser
644 -- sees it as lazy. Then the worker/wrapper phase inlines it.
649 -- Assertion function. This simply ignores its boolean argument.
650 -- The compiler may rewrite it to (assertError line)
651 -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
652 -- but from Template Haskell onwards it's simply
653 -- defined here in Base.lhs
654 assert :: Bool -> a -> a
661 -- function composition
663 (.) :: (b -> c) -> (a -> b) -> a -> c
666 -- flip f takes its (first) two arguments in the reverse order of f.
667 flip :: (a -> b -> c) -> b -> a -> c
670 -- right-associating infix application operator (useful in continuation-
673 ($) :: (a -> b) -> a -> b
676 -- until p f yields the result of applying f until p holds.
677 until :: (a -> Bool) -> (a -> a) -> a -> a
678 until p f x | p x = x
679 | otherwise = until p f (f x)
681 -- asTypeOf is a type-restricted version of const. It is usually used
682 -- as an infix operator, and its typing forces its first argument
683 -- (which is usually overloaded) to have the same type as the second.
684 asTypeOf :: a -> a -> a
688 %*********************************************************
690 \subsection{Generics}
692 %*********************************************************
697 data (:+:) a b = Inl a | Inr b
698 data (:*:) a b = a :*: b
702 %*********************************************************
704 \subsection{@getTag@}
706 %*********************************************************
708 Returns the 'tag' of a constructor application; this function is used
709 by the deriving code for Eq, Ord and Enum.
711 The primitive dataToTag# requires an evaluated constructor application
712 as its argument, so we provide getTag as a wrapper that performs the
713 evaluation before calling dataToTag#. We could have dataToTag#
714 evaluate its argument, but we prefer to do it this way because (a)
715 dataToTag# can be an inline primop if it doesn't need to do any
716 evaluation, and (b) we want to expose the evaluation to the
717 simplifier, because it might be possible to eliminate the evaluation
718 in the case when the argument is already known to be evaluated.
721 {-# INLINE getTag #-}
723 getTag x = x `seq` dataToTag# x
726 %*********************************************************
728 \subsection{Numeric primops}
730 %*********************************************************
733 divInt# :: Int# -> Int# -> Int#
735 -- Be careful NOT to overflow if we do any additional arithmetic
736 -- on the arguments... the following previous version of this
737 -- code has problems with overflow:
738 -- | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
739 -- | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
740 | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
741 | (x# <# 0#) && (y# ># 0#) = ((x# +# 1#) `quotInt#` y#) -# 1#
742 | otherwise = x# `quotInt#` y#
744 modInt# :: Int# -> Int# -> Int#
746 | (x# ># 0#) && (y# <# 0#) ||
747 (x# <# 0#) && (y# ># 0#) = if r# /=# 0# then r# +# y# else 0#
753 Definitions of the boxed PrimOps; these will be
754 used in the case of partial applications, etc.
763 {-# INLINE plusInt #-}
764 {-# INLINE minusInt #-}
765 {-# INLINE timesInt #-}
766 {-# INLINE quotInt #-}
767 {-# INLINE remInt #-}
768 {-# INLINE negateInt #-}
770 plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt, gcdInt :: Int -> Int -> Int
771 (I# x) `plusInt` (I# y) = I# (x +# y)
772 (I# x) `minusInt` (I# y) = I# (x -# y)
773 (I# x) `timesInt` (I# y) = I# (x *# y)
774 (I# x) `quotInt` (I# y) = I# (x `quotInt#` y)
775 (I# x) `remInt` (I# y) = I# (x `remInt#` y)
776 (I# x) `divInt` (I# y) = I# (x `divInt#` y)
777 (I# x) `modInt` (I# y) = I# (x `modInt#` y)
780 "x# +# 0#" forall x#. x# +# 0# = x#
781 "0# +# x#" forall x#. 0# +# x# = x#
782 "x# -# 0#" forall x#. x# -# 0# = x#
783 "x# -# x#" forall x#. x# -# x# = 0#
784 "x# *# 0#" forall x#. x# *# 0# = 0#
785 "0# *# x#" forall x#. 0# *# x# = 0#
786 "x# *# 1#" forall x#. x# *# 1# = x#
787 "1# *# x#" forall x#. 1# *# x# = x#
790 gcdInt (I# a) (I# b) = g a b
791 where g 0# 0# = error "GHC.Base.gcdInt: gcd 0 0 is undefined"
794 g _ _ = I# (gcdInt# absA absB)
796 absInt x = if x <# 0# then negateInt# x else x
801 negateInt :: Int -> Int
802 negateInt (I# x) = I# (negateInt# x)
804 gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
805 (I# x) `gtInt` (I# y) = x ># y
806 (I# x) `geInt` (I# y) = x >=# y
807 (I# x) `eqInt` (I# y) = x ==# y
808 (I# x) `neInt` (I# y) = x /=# y
809 (I# x) `ltInt` (I# y) = x <# y
810 (I# x) `leInt` (I# y) = x <=# y
813 "x# ># x#" forall x#. x# ># x# = False
814 "x# >=# x#" forall x#. x# >=# x# = True
815 "x# ==# x#" forall x#. x# ==# x# = True
816 "x# /=# x#" forall x#. x# /=# x# = False
817 "x# <# x#" forall x#. x# <# x# = False
818 "x# <=# x#" forall x#. x# <=# x# = True
822 "plusFloat x 0.0" forall x#. plusFloat# x# 0.0# = x#
823 "plusFloat 0.0 x" forall x#. plusFloat# 0.0# x# = x#
824 "minusFloat x 0.0" forall x#. minusFloat# x# 0.0# = x#
825 "minusFloat x x" forall x#. minusFloat# x# x# = 0.0#
826 "timesFloat x 0.0" forall x#. timesFloat# x# 0.0# = 0.0#
827 "timesFloat0.0 x" forall x#. timesFloat# 0.0# x# = 0.0#
828 "timesFloat x 1.0" forall x#. timesFloat# x# 1.0# = x#
829 "timesFloat 1.0 x" forall x#. timesFloat# 1.0# x# = x#
830 "divideFloat x 1.0" forall x#. divideFloat# x# 1.0# = x#
834 "plusDouble x 0.0" forall x#. (+##) x# 0.0## = x#
835 "plusDouble 0.0 x" forall x#. (+##) 0.0## x# = x#
836 "minusDouble x 0.0" forall x#. (-##) x# 0.0## = x#
837 "minusDouble x x" forall x#. (-##) x# x# = 0.0##
838 "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
839 "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
840 "timesDouble x 1.0" forall x#. (*##) x# 1.0## = x#
841 "timesDouble 1.0 x" forall x#. (*##) 1.0## x# = x#
842 "divideDouble x 1.0" forall x#. (/##) x# 1.0## = x#
845 -- Wrappers for the shift operations. The uncheckedShift# family are
846 -- undefined when the amount being shifted by is greater than the size
847 -- in bits of Int#, so these wrappers perform a check and return
848 -- either zero or -1 appropriately.
850 -- Note that these wrappers still produce undefined results when the
851 -- second argument (the shift amount) is negative.
853 shiftL#, shiftRL# :: Word# -> Int# -> Word#
855 a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
856 | otherwise = a `uncheckedShiftL#` b
858 a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
859 | otherwise = a `uncheckedShiftRL#` b
861 iShiftL#, iShiftRA#, iShiftRL# :: Int# -> Int# -> Int#
863 a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
864 | otherwise = a `uncheckedIShiftL#` b
866 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
867 | otherwise = a `uncheckedIShiftRA#` b
869 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
870 | otherwise = a `uncheckedIShiftRL#` b
872 #if WORD_SIZE_IN_BITS == 32
874 "narrow32Int#" forall x#. narrow32Int# x# = x#
875 "narrow32Word#" forall x#. narrow32Word# x# = x#
880 "int2Word2Int" forall x#. int2Word# (word2Int# x#) = x#
881 "word2Int2Word" forall x#. word2Int# (int2Word# x#) = x#
886 %********************************************************
888 \subsection{Unpacking C strings}
890 %********************************************************
892 This code is needed for virtually all programs, since it's used for
893 unpacking the strings of error messages.
896 unpackCString# :: Addr# -> [Char]
897 {-# NOINLINE [1] unpackCString# #-}
902 | ch `eqChar#` '\0'# = []
903 | otherwise = C# ch : unpack (nh +# 1#)
905 ch = indexCharOffAddr# addr nh
907 unpackAppendCString# :: Addr# -> [Char] -> [Char]
908 unpackAppendCString# addr rest
912 | ch `eqChar#` '\0'# = rest
913 | otherwise = C# ch : unpack (nh +# 1#)
915 ch = indexCharOffAddr# addr nh
917 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
918 {-# NOINLINE [0] unpackFoldrCString# #-}
919 -- Don't inline till right at the end;
920 -- usually the unpack-list rule turns it into unpackCStringList
921 unpackFoldrCString# addr f z
925 | ch `eqChar#` '\0'# = z
926 | otherwise = C# ch `f` unpack (nh +# 1#)
928 ch = indexCharOffAddr# addr nh
930 unpackCStringUtf8# :: Addr# -> [Char]
931 unpackCStringUtf8# addr
935 | ch `eqChar#` '\0'# = []
936 | ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
937 | ch `leChar#` '\xDF'# =
938 C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
939 (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
941 | ch `leChar#` '\xEF'# =
942 C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
943 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
944 (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
947 C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
948 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
949 ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
950 (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
953 ch = indexCharOffAddr# addr nh
955 unpackNBytes# :: Addr# -> Int# -> [Char]
956 unpackNBytes# _addr 0# = []
957 unpackNBytes# addr len# = unpack [] (len# -# 1#)
962 case indexCharOffAddr# addr i# of
963 ch -> unpack (C# ch : acc) (i# -# 1#)
966 "unpack" [~1] forall a . unpackCString# a = build (unpackFoldrCString# a)
967 "unpack-list" [1] forall a . unpackFoldrCString# a (:) [] = unpackCString# a
968 "unpack-append" forall a n . unpackFoldrCString# a (:) n = unpackAppendCString# a n
970 -- There's a built-in rule (in PrelRules.lhs) for
971 -- unpackFoldr "foo" c (unpackFoldr "baz" c n) = unpackFoldr "foobaz" c n
978 -- | A special argument for the 'Control.Monad.ST.ST' type constructor,
979 -- indexing a state embedded in the 'Prelude.IO' monad by
980 -- 'Control.Monad.ST.stToIO'.