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 (>>=) :: m a -> (a -> m b) -> m b
227 (>>) :: m a -> m b -> m b
229 fail :: String -> m a
231 m >> k = m >>= \_ -> k
236 %*********************************************************
238 \subsection{The list type}
240 %*********************************************************
243 data [] a = [] | a : [a] -- do explicitly: deriving (Eq, Ord)
244 -- to avoid weird names like con2tag_[]#
247 instance (Eq a) => Eq [a] where
248 {-# SPECIALISE instance Eq [Char] #-}
250 (x:xs) == (y:ys) = x == y && xs == ys
253 instance (Ord a) => Ord [a] where
254 {-# SPECIALISE instance Ord [Char] #-}
256 compare [] (_:_) = LT
257 compare (_:_) [] = GT
258 compare (x:xs) (y:ys) = case compare x y of
262 instance Functor [] where
265 instance Monad [] where
266 m >>= k = foldr ((++) . k) [] m
267 m >> k = foldr ((++) . (\ _ -> k)) [] m
272 A few list functions that appear here because they are used here.
273 The rest of the prelude list functions are in GHC.List.
275 ----------------------------------------------
276 -- foldr/build/augment
277 ----------------------------------------------
280 -- | 'foldr', applied to a binary operator, a starting value (typically
281 -- the right-identity of the operator), and a list, reduces the list
282 -- using the binary operator, from right to left:
284 -- > foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
286 foldr :: (a -> b -> b) -> b -> [a] -> b
288 -- foldr f z (x:xs) = f x (foldr f z xs)
289 {-# INLINE [0] foldr #-}
290 -- Inline only in the final stage, after the foldr/cons rule has had a chance
294 go (y:ys) = y `k` go ys
296 build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
297 {-# INLINE [1] build #-}
298 -- The INLINE is important, even though build is tiny,
299 -- because it prevents [] getting inlined in the version that
300 -- appears in the interface file. If [] *is* inlined, it
301 -- won't match with [] appearing in rules in an importing module.
303 -- The "1" says to inline in phase 1
307 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
308 {-# INLINE [1] augment #-}
309 augment g xs = g (:) xs
312 "fold/build" forall k z (g::forall b. (a->b->b) -> b -> b) .
313 foldr k z (build g) = g k z
315 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) .
316 foldr k z (augment g xs) = g k (foldr k z xs)
318 "foldr/id" foldr (:) [] = \x->x
319 "foldr/app" [1] forall xs ys. foldr (:) ys xs = xs ++ ys
320 -- Only activate this from phase 1, because that's
321 -- when we disable the rule that expands (++) into foldr
323 -- The foldr/cons rule looks nice, but it can give disastrously
324 -- bloated code when commpiling
325 -- array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]
326 -- i.e. when there are very very long literal lists
327 -- So I've disabled it for now. We could have special cases
328 -- for short lists, I suppose.
329 -- "foldr/cons" forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)
331 "foldr/single" forall k z x. foldr k z [x] = k x z
332 "foldr/nil" forall k z. foldr k z [] = z
334 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)
335 (h::forall b. (a->b->b) -> b -> b) .
336 augment g (build h) = build (\c n -> g c (h c n))
337 "augment/nil" forall (g::forall b. (a->b->b) -> b -> b) .
338 augment g [] = build g
341 -- This rule is true, but not (I think) useful:
342 -- augment g (augment h t) = augment (\cn -> g c (h c n)) t
346 ----------------------------------------------
348 ----------------------------------------------
351 -- | 'map' @f xs@ is the list obtained by applying @f@ to each element
354 -- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
355 -- > map f [x1, x2, ...] == [f x1, f x2, ...]
357 map :: (a -> b) -> [a] -> [b]
359 map f (x:xs) = f x : map f xs
362 mapFB :: (elt -> lst -> lst) -> (a -> elt) -> a -> lst -> lst
363 {-# INLINE [0] mapFB #-}
364 mapFB c f x ys = c (f x) ys
366 -- The rules for map work like this.
368 -- Up to (but not including) phase 1, we use the "map" rule to
369 -- rewrite all saturated applications of map with its build/fold
370 -- form, hoping for fusion to happen.
371 -- In phase 1 and 0, we switch off that rule, inline build, and
372 -- switch on the "mapList" rule, which rewrites the foldr/mapFB
373 -- thing back into plain map.
375 -- It's important that these two rules aren't both active at once
376 -- (along with build's unfolding) else we'd get an infinite loop
377 -- in the rules. Hence the activation control below.
379 -- The "mapFB" rule optimises compositions of map.
381 -- This same pattern is followed by many other functions:
382 -- e.g. append, filter, iterate, repeat, etc.
385 "map" [~1] forall f xs. map f xs = build (\c n -> foldr (mapFB c f) n xs)
386 "mapList" [1] forall f. foldr (mapFB (:) f) [] = map f
387 "mapFB" forall c f g. mapFB (mapFB c f) g = mapFB c (f.g)
392 ----------------------------------------------
394 ----------------------------------------------
396 -- | Append two lists, i.e.,
398 -- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
399 -- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
401 -- If the first list is not finite, the result is the first list.
403 (++) :: [a] -> [a] -> [a]
405 (++) (x:xs) ys = x : xs ++ ys
408 "++" [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys
414 %*********************************************************
416 \subsection{Type @Bool@}
418 %*********************************************************
421 -- |The 'Bool' type is an enumeration. It is defined with 'False'
422 -- first so that the corresponding 'Prelude.Enum' instance will give
423 -- 'Prelude.fromEnum' 'False' the value zero, and
424 -- 'Prelude.fromEnum' 'True' the value 1.
425 data Bool = False | True deriving (Eq, Ord)
426 -- Read in GHC.Read, Show in GHC.Show
431 (&&) :: Bool -> Bool -> Bool
436 (||) :: Bool -> Bool -> Bool
445 -- |'otherwise' is defined as the value 'True'. It helps to make
446 -- guards more readable. eg.
448 -- > f x | x < 0 = ...
449 -- > | otherwise = ...
455 %*********************************************************
457 \subsection{The @()@ type}
459 %*********************************************************
461 The Unit type is here because virtually any program needs it (whereas
462 some programs may get away without consulting GHC.Tup). Furthermore,
463 the renamer currently *always* asks for () to be in scope, so that
464 ccalls can use () as their default type; so when compiling GHC.Base we
465 need (). (We could arrange suck in () only if -fglasgow-exts, but putting
466 it here seems more direct.)
469 -- | The unit datatype @()@ has one non-undefined member, the nullary
477 instance Ord () where
488 %*********************************************************
490 \subsection{Type @Ordering@}
492 %*********************************************************
495 -- | Represents an ordering relationship between two values: less
496 -- than, equal to, or greater than. An 'Ordering' is returned by
498 data Ordering = LT | EQ | GT deriving (Eq, Ord)
499 -- Read in GHC.Read, Show in GHC.Show
503 %*********************************************************
505 \subsection{Type @Char@ and @String@}
507 %*********************************************************
510 -- | A 'String' is a list of characters. String constants in Haskell are values
515 {-| The character type 'Char' is an enumeration whose values represent
516 Unicode (or equivalently ISO 10646) characters.
517 This set extends the ISO 8859-1 (Latin-1) character set
518 (the first 256 charachers), which is itself an extension of the ASCII
519 character set (the first 128 characters).
520 A character literal in Haskell has type 'Char'.
522 To convert a 'Char' to or from the corresponding 'Int' value defined
523 by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
524 'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
528 -- We don't use deriving for Eq and Ord, because for Ord the derived
529 -- instance defines only compare, which takes two primops. Then
530 -- '>' uses compare, and therefore takes two primops instead of one.
532 instance Eq Char where
533 (C# c1) == (C# c2) = c1 `eqChar#` c2
534 (C# c1) /= (C# c2) = c1 `neChar#` c2
536 instance Ord Char where
537 (C# c1) > (C# c2) = c1 `gtChar#` c2
538 (C# c1) >= (C# c2) = c1 `geChar#` c2
539 (C# c1) <= (C# c2) = c1 `leChar#` c2
540 (C# c1) < (C# c2) = c1 `ltChar#` c2
543 "x# `eqChar#` x#" forall x#. x# `eqChar#` x# = True
544 "x# `neChar#` x#" forall x#. x# `neChar#` x# = False
545 "x# `gtChar#` x#" forall x#. x# `gtChar#` x# = False
546 "x# `geChar#` x#" forall x#. x# `geChar#` x# = True
547 "x# `leChar#` x#" forall x#. x# `leChar#` x# = True
548 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
551 -- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
553 chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
554 | otherwise = error "Prelude.chr: bad argument"
556 unsafeChr :: Int -> Char
557 unsafeChr (I# i#) = C# (chr# i#)
559 -- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
561 ord (C# c#) = I# (ord# c#)
564 String equality is used when desugaring pattern-matches against strings.
567 eqString :: String -> String -> Bool
568 eqString [] [] = True
569 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
570 eqString cs1 cs2 = False
572 {-# RULES "eqString" (==) = eqString #-}
576 %*********************************************************
578 \subsection{Type @Int@}
580 %*********************************************************
584 -- ^A fixed-precision integer type with at least the range @[-2^29
585 -- .. 2^29-1]@. The exact range for a given implementation can be
586 -- determined by using 'minBound' and 'maxBound' from the 'Bounded'
589 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
594 {- Seems clumsy. Should perhaps put minInt and MaxInt directly into MachDeps.h -}
595 #if WORD_SIZE_IN_BITS == 31
596 minInt = I# (-0x40000000#)
597 maxInt = I# 0x3FFFFFFF#
598 #elif WORD_SIZE_IN_BITS == 32
599 minInt = I# (-0x80000000#)
600 maxInt = I# 0x7FFFFFFF#
602 minInt = I# (-0x8000000000000000#)
603 maxInt = I# 0x7FFFFFFFFFFFFFFF#
606 instance Eq Int where
610 instance Ord Int where
617 compareInt :: Int -> Int -> Ordering
618 (I# x#) `compareInt` (I# y#) = compareInt# x# y#
620 compareInt# :: Int# -> Int# -> Ordering
628 %*********************************************************
630 \subsection{The function type}
632 %*********************************************************
639 -- lazy function; this is just the same as id, but its unfolding
640 -- and strictness are over-ridden by the definition in MkId.lhs
641 -- That way, it does not get inlined, and the strictness analyser
642 -- sees it as lazy. Then the worker/wrapper phase inlines it.
647 -- Assertion function. This simply ignores its boolean argument.
648 -- The compiler may rewrite it to (assertError line)
649 -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
650 -- but from Template Haskell onwards it's simply
651 -- defined here in Base.lhs
652 assert :: Bool -> a -> a
659 -- function composition
661 (.) :: (b -> c) -> (a -> b) -> a -> c
664 -- flip f takes its (first) two arguments in the reverse order of f.
665 flip :: (a -> b -> c) -> b -> a -> c
668 -- right-associating infix application operator (useful in continuation-
671 ($) :: (a -> b) -> a -> b
674 -- until p f yields the result of applying f until p holds.
675 until :: (a -> Bool) -> (a -> a) -> a -> a
676 until p f x | p x = x
677 | otherwise = until p f (f x)
679 -- asTypeOf is a type-restricted version of const. It is usually used
680 -- as an infix operator, and its typing forces its first argument
681 -- (which is usually overloaded) to have the same type as the second.
682 asTypeOf :: a -> a -> a
686 %*********************************************************
688 \subsection{Generics}
690 %*********************************************************
695 data (:+:) a b = Inl a | Inr b
696 data (:*:) a b = a :*: b
700 %*********************************************************
702 \subsection{@getTag@}
704 %*********************************************************
706 Returns the 'tag' of a constructor application; this function is used
707 by the deriving code for Eq, Ord and Enum.
709 The primitive dataToTag# requires an evaluated constructor application
710 as its argument, so we provide getTag as a wrapper that performs the
711 evaluation before calling dataToTag#. We could have dataToTag#
712 evaluate its argument, but we prefer to do it this way because (a)
713 dataToTag# can be an inline primop if it doesn't need to do any
714 evaluation, and (b) we want to expose the evaluation to the
715 simplifier, because it might be possible to eliminate the evaluation
716 in the case when the argument is already known to be evaluated.
719 {-# INLINE getTag #-}
721 getTag x = x `seq` dataToTag# x
724 %*********************************************************
726 \subsection{Numeric primops}
728 %*********************************************************
731 divInt# :: Int# -> Int# -> Int#
733 -- Be careful NOT to overflow if we do any additional arithmetic
734 -- on the arguments... the following previous version of this
735 -- code has problems with overflow:
736 -- | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
737 -- | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
738 | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
739 | (x# <# 0#) && (y# ># 0#) = ((x# +# 1#) `quotInt#` y#) -# 1#
740 | otherwise = x# `quotInt#` y#
742 modInt# :: Int# -> Int# -> Int#
744 | (x# ># 0#) && (y# <# 0#) ||
745 (x# <# 0#) && (y# ># 0#) = if r# /=# 0# then r# +# y# else 0#
751 Definitions of the boxed PrimOps; these will be
752 used in the case of partial applications, etc.
761 {-# INLINE plusInt #-}
762 {-# INLINE minusInt #-}
763 {-# INLINE timesInt #-}
764 {-# INLINE quotInt #-}
765 {-# INLINE remInt #-}
766 {-# INLINE negateInt #-}
768 plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt, gcdInt :: Int -> Int -> Int
769 (I# x) `plusInt` (I# y) = I# (x +# y)
770 (I# x) `minusInt` (I# y) = I# (x -# y)
771 (I# x) `timesInt` (I# y) = I# (x *# y)
772 (I# x) `quotInt` (I# y) = I# (x `quotInt#` y)
773 (I# x) `remInt` (I# y) = I# (x `remInt#` y)
774 (I# x) `divInt` (I# y) = I# (x `divInt#` y)
775 (I# x) `modInt` (I# y) = I# (x `modInt#` y)
778 "x# +# 0#" forall x#. x# +# 0# = x#
779 "0# +# x#" forall x#. 0# +# x# = x#
780 "x# -# 0#" forall x#. x# -# 0# = x#
781 "x# -# x#" forall x#. x# -# x# = 0#
782 "x# *# 0#" forall x#. x# *# 0# = 0#
783 "0# *# x#" forall x#. 0# *# x# = 0#
784 "x# *# 1#" forall x#. x# *# 1# = x#
785 "1# *# x#" forall x#. 1# *# x# = x#
788 gcdInt (I# a) (I# b) = g a b
789 where g 0# 0# = error "GHC.Base.gcdInt: gcd 0 0 is undefined"
792 g _ _ = I# (gcdInt# absA absB)
794 absInt x = if x <# 0# then negateInt# x else x
799 negateInt :: Int -> Int
800 negateInt (I# x) = I# (negateInt# x)
802 gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
803 (I# x) `gtInt` (I# y) = x ># y
804 (I# x) `geInt` (I# y) = x >=# y
805 (I# x) `eqInt` (I# y) = x ==# y
806 (I# x) `neInt` (I# y) = x /=# y
807 (I# x) `ltInt` (I# y) = x <# y
808 (I# x) `leInt` (I# y) = x <=# y
811 "x# ># x#" forall x#. x# ># x# = False
812 "x# >=# x#" forall x#. x# >=# x# = True
813 "x# ==# x#" forall x#. x# ==# x# = True
814 "x# /=# x#" forall x#. x# /=# x# = False
815 "x# <# x#" forall x#. x# <# x# = False
816 "x# <=# x#" forall x#. x# <=# x# = True
820 "plusFloat x 0.0" forall x#. plusFloat# x# 0.0# = x#
821 "plusFloat 0.0 x" forall x#. plusFloat# 0.0# x# = x#
822 "minusFloat x 0.0" forall x#. minusFloat# x# 0.0# = x#
823 "minusFloat x x" forall x#. minusFloat# x# x# = 0.0#
824 "timesFloat x 0.0" forall x#. timesFloat# x# 0.0# = 0.0#
825 "timesFloat0.0 x" forall x#. timesFloat# 0.0# x# = 0.0#
826 "timesFloat x 1.0" forall x#. timesFloat# x# 1.0# = x#
827 "timesFloat 1.0 x" forall x#. timesFloat# 1.0# x# = x#
828 "divideFloat x 1.0" forall x#. divideFloat# x# 1.0# = x#
832 "plusDouble x 0.0" forall x#. (+##) x# 0.0## = x#
833 "plusDouble 0.0 x" forall x#. (+##) 0.0## x# = x#
834 "minusDouble x 0.0" forall x#. (-##) x# 0.0## = x#
835 "minusDouble x x" forall x#. (-##) x# x# = 0.0##
836 "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
837 "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
838 "timesDouble x 1.0" forall x#. (*##) x# 1.0## = x#
839 "timesDouble 1.0 x" forall x#. (*##) 1.0## x# = x#
840 "divideDouble x 1.0" forall x#. (/##) x# 1.0## = x#
843 -- Wrappers for the shift operations. The uncheckedShift# family are
844 -- undefined when the amount being shifted by is greater than the size
845 -- in bits of Int#, so these wrappers perform a check and return
846 -- either zero or -1 appropriately.
848 -- Note that these wrappers still produce undefined results when the
849 -- second argument (the shift amount) is negative.
851 shiftL#, shiftRL# :: Word# -> Int# -> Word#
853 a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
854 | otherwise = a `uncheckedShiftL#` b
856 a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
857 | otherwise = a `uncheckedShiftRL#` b
859 iShiftL#, iShiftRA#, iShiftRL# :: Int# -> Int# -> Int#
861 a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
862 | otherwise = a `uncheckedIShiftL#` b
864 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
865 | otherwise = a `uncheckedIShiftRA#` b
867 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
868 | otherwise = a `uncheckedIShiftRL#` b
870 #if WORD_SIZE_IN_BITS == 32
872 "narrow32Int#" forall x#. narrow32Int# x# = x#
873 "narrow32Word#" forall x#. narrow32Word# x# = x#
878 "int2Word2Int" forall x#. int2Word# (word2Int# x#) = x#
879 "word2Int2Word" forall x#. word2Int# (int2Word# x#) = x#
884 %********************************************************
886 \subsection{Unpacking C strings}
888 %********************************************************
890 This code is needed for virtually all programs, since it's used for
891 unpacking the strings of error messages.
894 unpackCString# :: Addr# -> [Char]
895 {-# NOINLINE [1] unpackCString# #-}
900 | ch `eqChar#` '\0'# = []
901 | otherwise = C# ch : unpack (nh +# 1#)
903 ch = indexCharOffAddr# addr nh
905 unpackAppendCString# :: Addr# -> [Char] -> [Char]
906 unpackAppendCString# addr rest
910 | ch `eqChar#` '\0'# = rest
911 | otherwise = C# ch : unpack (nh +# 1#)
913 ch = indexCharOffAddr# addr nh
915 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
916 {-# NOINLINE [0] unpackFoldrCString# #-}
917 -- Don't inline till right at the end;
918 -- usually the unpack-list rule turns it into unpackCStringList
919 unpackFoldrCString# addr f z
923 | ch `eqChar#` '\0'# = z
924 | otherwise = C# ch `f` unpack (nh +# 1#)
926 ch = indexCharOffAddr# addr nh
928 unpackCStringUtf8# :: Addr# -> [Char]
929 unpackCStringUtf8# addr
933 | ch `eqChar#` '\0'# = []
934 | ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
935 | ch `leChar#` '\xDF'# =
936 C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
937 (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
939 | ch `leChar#` '\xEF'# =
940 C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
941 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
942 (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
945 C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
946 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
947 ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
948 (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
951 ch = indexCharOffAddr# addr nh
953 unpackNBytes# :: Addr# -> Int# -> [Char]
954 unpackNBytes# _addr 0# = []
955 unpackNBytes# addr len# = unpack [] (len# -# 1#)
960 case indexCharOffAddr# addr i# of
961 ch -> unpack (C# ch : acc) (i# -# 1#)
964 "unpack" [~1] forall a . unpackCString# a = build (unpackFoldrCString# a)
965 "unpack-list" [1] forall a . unpackFoldrCString# a (:) [] = unpackCString# a
966 "unpack-append" forall a n . unpackFoldrCString# a (:) n = unpackAppendCString# a n
968 -- There's a built-in rule (in PrelRules.lhs) for
969 -- unpackFoldr "foo" c (unpackFoldr "baz" c n) = unpackFoldr "foobaz" c n
976 -- | A special argument for the 'Control.Monad.ST.ST' type constructor,
977 -- indexing a state embedded in the 'Prelude.IO' monad by
978 -- 'Control.Monad.ST.stToIO'.