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.Tuple 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.List List functions
32 GHC.Num Class: Num, plus instances for Int
33 Type: Integer, plus instances for all classes so far (Eq, Ord, Num, Show)
35 Integer is needed here because it is mentioned in the signature
36 of 'fromInteger' in class Num
38 GHC.Real Classes: Real, Integral, Fractional, RealFrac
39 plus instances for Int, Integer
40 Types: Ratio, Rational
41 plus intances for classes so far
43 Rational is needed here because it is mentioned in the signature
44 of 'toRational' in class Real
46 GHC.ST The ST monad, instances and a few helper functions
48 Ix Classes: Ix, plus instances for Int, Bool, Char, Integer, Ordering, tuples
50 GHC.Arr Types: Array, MutableArray, MutableVar
52 Arrays are used by a function in GHC.Float
54 GHC.Float Classes: Floating, RealFloat
55 Types: Float, Double, plus instances of all classes so far
57 This module contains everything to do with floating point.
58 It is a big module (900 lines)
59 With a bit of luck, many modules can be compiled without ever reading GHC.Float.hi
62 Other Prelude modules are much easier with fewer complex dependencies.
65 {-# OPTIONS_GHC -XNoImplicitPrelude #-}
66 -- -fno-warn-orphans is needed for things like:
67 -- Orphan rule: "x# -# x#" ALWAYS forall x# :: Int# -# x# x# = 0
68 {-# OPTIONS_GHC -fno-warn-orphans #-}
69 {-# OPTIONS_HADDOCK hide #-}
70 -----------------------------------------------------------------------------
73 -- Copyright : (c) The University of Glasgow, 1992-2002
74 -- License : see libraries/base/LICENSE
76 -- Maintainer : cvs-ghc@haskell.org
77 -- Stability : internal
78 -- Portability : non-portable (GHC extensions)
80 -- Basic data types and classes.
82 -----------------------------------------------------------------------------
95 module GHC.Prim, -- Re-export GHC.Prim and GHC.Err, to avoid lots
96 module GHC.Err -- of people having to import it explicitly
106 import {-# SOURCE #-} GHC.Show
107 import {-# SOURCE #-} GHC.Err
108 import {-# SOURCE #-} GHC.IO (failIO)
110 -- These two are not strictly speaking required by this module, but they are
111 -- implicit dependencies whenever () or tuples are mentioned, so adding them
112 -- as imports here helps to get the dependencies right in the new build system.
122 default () -- Double isn't available yet
126 %*********************************************************
128 \subsection{DEBUGGING STUFF}
129 %* (for use when compiling GHC.Base itself doesn't work)
131 %*********************************************************
135 data Bool = False | True
136 data Ordering = LT | EQ | GT
144 (&&) True True = True
150 unpackCString# :: Addr# -> [Char]
151 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
152 unpackAppendCString# :: Addr# -> [Char] -> [Char]
153 unpackCStringUtf8# :: Addr# -> [Char]
154 unpackCString# a = error "urk"
155 unpackFoldrCString# a = error "urk"
156 unpackAppendCString# a = error "urk"
157 unpackCStringUtf8# a = error "urk"
162 %*********************************************************
164 \subsection{Monadic classes @Functor@, @Monad@ }
166 %*********************************************************
169 {- | The 'Functor' class is used for types that can be mapped over.
170 Instances of 'Functor' should satisfy the following laws:
173 > fmap (f . g) == fmap f . fmap g
175 The instances of 'Functor' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
176 defined in the "Prelude" satisfy these laws.
179 class Functor f where
180 fmap :: (a -> b) -> f a -> f b
182 -- | Replace all locations in the input with the same value.
183 -- The default definition is @'fmap' . 'const'@, but this may be
184 -- overridden with a more efficient version.
185 (<$) :: a -> f b -> f a
188 {- | The 'Monad' class defines the basic operations over a /monad/,
189 a concept from a branch of mathematics known as /category theory/.
190 From the perspective of a Haskell programmer, however, it is best to
191 think of a monad as an /abstract datatype/ of actions.
192 Haskell's @do@ expressions provide a convenient syntax for writing
195 Minimal complete definition: '>>=' and 'return'.
197 Instances of 'Monad' should satisfy the following laws:
199 > return a >>= k == k a
201 > m >>= (\x -> k x >>= h) == (m >>= k) >>= h
203 Instances of both 'Monad' and 'Functor' should additionally satisfy the law:
205 > fmap f xs == xs >>= return . f
207 The instances of 'Monad' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
208 defined in the "Prelude" satisfy these laws.
212 -- | Sequentially compose two actions, passing any value produced
213 -- by the first as an argument to the second.
214 (>>=) :: forall a b. m a -> (a -> m b) -> m b
215 -- | Sequentially compose two actions, discarding any value produced
216 -- by the first, like sequencing operators (such as the semicolon)
217 -- in imperative languages.
218 (>>) :: forall a b. m a -> m b -> m b
219 -- Explicit for-alls so that we know what order to
220 -- give type arguments when desugaring
222 -- | Inject a value into the monadic type.
224 -- | Fail with a message. This operation is not part of the
225 -- mathematical definition of a monad, but is invoked on pattern-match
226 -- failure in a @do@ expression.
227 fail :: String -> m a
230 m >> k = m >>= \_ -> k
235 %*********************************************************
237 \subsection{The list type}
239 %*********************************************************
242 instance Functor [] where
245 instance Monad [] where
246 m >>= k = foldr ((++) . k) [] m
247 m >> k = foldr ((++) . (\ _ -> k)) [] m
252 A few list functions that appear here because they are used here.
253 The rest of the prelude list functions are in GHC.List.
255 ----------------------------------------------
256 -- foldr/build/augment
257 ----------------------------------------------
260 -- | 'foldr', applied to a binary operator, a starting value (typically
261 -- the right-identity of the operator), and a list, reduces the list
262 -- using the binary operator, from right to left:
264 -- > foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
266 foldr :: (a -> b -> b) -> b -> [a] -> b
268 -- foldr f z (x:xs) = f x (foldr f z xs)
269 {-# INLINE [0] foldr #-}
270 -- Inline only in the final stage, after the foldr/cons rule has had a chance
271 -- Also note that we inline it when it has *two* parameters, which are the
272 -- ones we are keen about specialising!
276 go (y:ys) = y `k` go ys
278 -- | A list producer that can be fused with 'foldr'.
279 -- This function is merely
281 -- > build g = g (:) []
283 -- but GHC's simplifier will transform an expression of the form
284 -- @'foldr' k z ('build' g)@, which may arise after inlining, to @g k z@,
285 -- which avoids producing an intermediate list.
287 build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
288 {-# INLINE [1] build #-}
289 -- The INLINE is important, even though build is tiny,
290 -- because it prevents [] getting inlined in the version that
291 -- appears in the interface file. If [] *is* inlined, it
292 -- won't match with [] appearing in rules in an importing module.
294 -- The "1" says to inline in phase 1
298 -- | A list producer that can be fused with 'foldr'.
299 -- This function is merely
301 -- > augment g xs = g (:) xs
303 -- but GHC's simplifier will transform an expression of the form
304 -- @'foldr' k z ('augment' g xs)@, which may arise after inlining, to
305 -- @g k ('foldr' k z xs)@, which avoids producing an intermediate list.
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 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 -- |'otherwise' is defined as the value 'True'. It helps to make
422 -- guards more readable. eg.
424 -- > f x | x < 0 = ...
425 -- > | otherwise = ...
430 %*********************************************************
432 \subsection{Type @Char@ and @String@}
434 %*********************************************************
437 -- | A 'String' is a list of characters. String constants in Haskell are values
443 "x# `eqChar#` x#" forall x#. x# `eqChar#` x# = True
444 "x# `neChar#` x#" forall x#. x# `neChar#` x# = False
445 "x# `gtChar#` x#" forall x#. x# `gtChar#` x# = False
446 "x# `geChar#` x#" forall x#. x# `geChar#` x# = True
447 "x# `leChar#` x#" forall x#. x# `leChar#` x# = True
448 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
451 -- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
454 | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
456 = error ("Prelude.chr: bad argument: " ++ showSignedInt (I# 9#) i "")
458 unsafeChr :: Int -> Char
459 unsafeChr (I# i#) = C# (chr# i#)
461 -- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
463 ord (C# c#) = I# (ord# c#)
466 String equality is used when desugaring pattern-matches against strings.
469 eqString :: String -> String -> Bool
470 eqString [] [] = True
471 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
474 {-# RULES "eqString" (==) = eqString #-}
475 -- eqString also has a BuiltInRule in PrelRules.lhs:
476 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
480 %*********************************************************
482 \subsection{Type @Int@}
484 %*********************************************************
487 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
492 {- Seems clumsy. Should perhaps put minInt and MaxInt directly into MachDeps.h -}
493 #if WORD_SIZE_IN_BITS == 31
494 minInt = I# (-0x40000000#)
495 maxInt = I# 0x3FFFFFFF#
496 #elif WORD_SIZE_IN_BITS == 32
497 minInt = I# (-0x80000000#)
498 maxInt = I# 0x7FFFFFFF#
500 minInt = I# (-0x8000000000000000#)
501 maxInt = I# 0x7FFFFFFFFFFFFFFF#
504 instance Eq Int where
508 instance Ord Int where
515 compareInt :: Int -> Int -> Ordering
516 (I# x#) `compareInt` (I# y#) = compareInt# x# y#
518 compareInt# :: Int# -> Int# -> Ordering
526 %*********************************************************
528 \subsection{The function type}
530 %*********************************************************
533 -- | Identity function.
537 -- | The call '(lazy e)' means the same as 'e', but 'lazy' has a
538 -- magical strictness property: it is lazy in its first argument,
539 -- even though its semantics is strict.
542 -- Implementation note: its strictness and unfolding are over-ridden
543 -- by the definition in MkId.lhs; in both cases to nothing at all.
544 -- That way, 'lazy' does not get inlined, and the strictness analyser
545 -- sees it as lazy. Then the worker/wrapper phase inlines it.
548 -- Assertion function. This simply ignores its boolean argument.
549 -- The compiler may rewrite it to @('assertError' line)@.
551 -- | If the first argument evaluates to 'True', then the result is the
552 -- second argument. Otherwise an 'AssertionFailed' exception is raised,
553 -- containing a 'String' with the source file and line number of the
556 -- Assertions can normally be turned on or off with a compiler flag
557 -- (for GHC, assertions are normally on unless optimisation is turned on
558 -- with @-O@ or the @-fignore-asserts@
559 -- option is given). When assertions are turned off, the first
560 -- argument to 'assert' is ignored, and the second argument is
561 -- returned as the result.
563 -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
564 -- but from Template Haskell onwards it's simply
565 -- defined here in Base.lhs
566 assert :: Bool -> a -> a
572 breakpointCond :: Bool -> a -> a
573 breakpointCond _ r = r
575 data Opaque = forall a. O a
577 -- | Constant function.
581 -- | Function composition.
583 -- Make sure it has TWO args only on the left, so that it inlines
584 -- when applied to two functions, even if there is no final argument
585 (.) :: (b -> c) -> (a -> b) -> a -> c
586 (.) f g = \x -> f (g x)
588 -- | @'flip' f@ takes its (first) two arguments in the reverse order of @f@.
589 flip :: (a -> b -> c) -> b -> a -> c
592 -- | Application operator. This operator is redundant, since ordinary
593 -- application @(f x)@ means the same as @(f '$' x)@. However, '$' has
594 -- low, right-associative binding precedence, so it sometimes allows
595 -- parentheses to be omitted; for example:
597 -- > f $ g $ h x = f (g (h x))
599 -- It is also useful in higher-order situations, such as @'map' ('$' 0) xs@,
600 -- or @'Data.List.zipWith' ('$') fs xs@.
602 ($) :: (a -> b) -> a -> b
605 -- | @'until' p f@ yields the result of applying @f@ until @p@ holds.
606 until :: (a -> Bool) -> (a -> a) -> a -> a
607 until p f x | p x = x
608 | otherwise = until p f (f x)
610 -- | 'asTypeOf' is a type-restricted version of 'const'. It is usually
611 -- used as an infix operator, and its typing forces its first argument
612 -- (which is usually overloaded) to have the same type as the second.
613 asTypeOf :: a -> a -> a
617 %*********************************************************
619 \subsection{@Functor@ and @Monad@ instances for @IO@}
621 %*********************************************************
624 instance Functor IO where
625 fmap f x = x >>= (return . f)
627 instance Monad IO where
628 {-# INLINE return #-}
631 m >> k = m >>= \ _ -> k
634 fail s = GHC.IO.failIO s
636 returnIO :: a -> IO a
637 returnIO x = IO $ \ s -> (# s, x #)
639 bindIO :: IO a -> (a -> IO b) -> IO b
640 bindIO (IO m) k = IO $ \ s -> case m s of (# new_s, a #) -> unIO (k a) new_s
642 thenIO :: IO a -> IO b -> IO b
643 thenIO (IO m) k = IO $ \ s -> case m s of (# new_s, _ #) -> unIO k new_s
645 unIO :: IO a -> (State# RealWorld -> (# State# RealWorld, a #))
649 %*********************************************************
651 \subsection{@getTag@}
653 %*********************************************************
655 Returns the 'tag' of a constructor application; this function is used
656 by the deriving code for Eq, Ord and Enum.
658 The primitive dataToTag# requires an evaluated constructor application
659 as its argument, so we provide getTag as a wrapper that performs the
660 evaluation before calling dataToTag#. We could have dataToTag#
661 evaluate its argument, but we prefer to do it this way because (a)
662 dataToTag# can be an inline primop if it doesn't need to do any
663 evaluation, and (b) we want to expose the evaluation to the
664 simplifier, because it might be possible to eliminate the evaluation
665 in the case when the argument is already known to be evaluated.
668 {-# INLINE getTag #-}
670 getTag x = x `seq` dataToTag# x
673 %*********************************************************
675 \subsection{Numeric primops}
677 %*********************************************************
680 divInt# :: Int# -> Int# -> Int#
682 -- Be careful NOT to overflow if we do any additional arithmetic
683 -- on the arguments... the following previous version of this
684 -- code has problems with overflow:
685 -- | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
686 -- | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
687 | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
688 | (x# <# 0#) && (y# ># 0#) = ((x# +# 1#) `quotInt#` y#) -# 1#
689 | otherwise = x# `quotInt#` y#
691 modInt# :: Int# -> Int# -> Int#
693 | (x# ># 0#) && (y# <# 0#) ||
694 (x# <# 0#) && (y# ># 0#) = if r# /=# 0# then r# +# y# else 0#
697 !r# = x# `remInt#` y#
700 Definitions of the boxed PrimOps; these will be
701 used in the case of partial applications, etc.
710 {-# INLINE plusInt #-}
711 {-# INLINE minusInt #-}
712 {-# INLINE timesInt #-}
713 {-# INLINE quotInt #-}
714 {-# INLINE remInt #-}
715 {-# INLINE negateInt #-}
717 plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt :: Int -> Int -> Int
718 (I# x) `plusInt` (I# y) = I# (x +# y)
719 (I# x) `minusInt` (I# y) = I# (x -# y)
720 (I# x) `timesInt` (I# y) = I# (x *# y)
721 (I# x) `quotInt` (I# y) = I# (x `quotInt#` y)
722 (I# x) `remInt` (I# y) = I# (x `remInt#` y)
723 (I# x) `divInt` (I# y) = I# (x `divInt#` y)
724 (I# x) `modInt` (I# y) = I# (x `modInt#` y)
727 "x# +# 0#" forall x#. x# +# 0# = x#
728 "0# +# x#" forall x#. 0# +# x# = x#
729 "x# -# 0#" forall x#. x# -# 0# = x#
730 "x# -# x#" forall x#. x# -# x# = 0#
731 "x# *# 0#" forall x#. x# *# 0# = 0#
732 "0# *# x#" forall x#. 0# *# x# = 0#
733 "x# *# 1#" forall x#. x# *# 1# = x#
734 "1# *# x#" forall x#. 1# *# x# = x#
737 negateInt :: Int -> Int
738 negateInt (I# x) = I# (negateInt# x)
740 gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
741 (I# x) `gtInt` (I# y) = x ># y
742 (I# x) `geInt` (I# y) = x >=# y
743 (I# x) `eqInt` (I# y) = x ==# y
744 (I# x) `neInt` (I# y) = x /=# y
745 (I# x) `ltInt` (I# y) = x <# y
746 (I# x) `leInt` (I# y) = x <=# y
749 "x# ># x#" forall x#. x# ># x# = False
750 "x# >=# x#" forall x#. x# >=# x# = True
751 "x# ==# x#" forall x#. x# ==# x# = True
752 "x# /=# x#" forall x#. x# /=# x# = False
753 "x# <# x#" forall x#. x# <# x# = False
754 "x# <=# x#" forall x#. x# <=# x# = True
758 "plusFloat x 0.0" forall x#. plusFloat# x# 0.0# = x#
759 "plusFloat 0.0 x" forall x#. plusFloat# 0.0# x# = x#
760 "minusFloat x 0.0" forall x#. minusFloat# x# 0.0# = x#
761 "minusFloat x x" forall x#. minusFloat# x# x# = 0.0#
762 "timesFloat x 0.0" forall x#. timesFloat# x# 0.0# = 0.0#
763 "timesFloat0.0 x" forall x#. timesFloat# 0.0# x# = 0.0#
764 "timesFloat x 1.0" forall x#. timesFloat# x# 1.0# = x#
765 "timesFloat 1.0 x" forall x#. timesFloat# 1.0# x# = x#
766 "divideFloat x 1.0" forall x#. divideFloat# x# 1.0# = x#
770 "plusDouble x 0.0" forall x#. (+##) x# 0.0## = x#
771 "plusDouble 0.0 x" forall x#. (+##) 0.0## x# = x#
772 "minusDouble x 0.0" forall x#. (-##) x# 0.0## = x#
773 "timesDouble x 1.0" forall x#. (*##) x# 1.0## = x#
774 "timesDouble 1.0 x" forall x#. (*##) 1.0## x# = x#
775 "divideDouble x 1.0" forall x#. (/##) x# 1.0## = x#
779 We'd like to have more rules, but for example:
781 This gives wrong answer (0) for NaN - NaN (should be NaN):
782 "minusDouble x x" forall x#. (-##) x# x# = 0.0##
784 This gives wrong answer (0) for 0 * NaN (should be NaN):
785 "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
787 This gives wrong answer (0) for NaN * 0 (should be NaN):
788 "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
790 These are tested by num014.
793 -- Wrappers for the shift operations. The uncheckedShift# family are
794 -- undefined when the amount being shifted by is greater than the size
795 -- in bits of Int#, so these wrappers perform a check and return
796 -- either zero or -1 appropriately.
798 -- Note that these wrappers still produce undefined results when the
799 -- second argument (the shift amount) is negative.
801 -- | Shift the argument left by the specified number of bits
802 -- (which must be non-negative).
803 shiftL# :: Word# -> Int# -> Word#
804 a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
805 | otherwise = a `uncheckedShiftL#` b
807 -- | Shift the argument right by the specified number of bits
808 -- (which must be non-negative).
809 shiftRL# :: Word# -> Int# -> Word#
810 a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
811 | otherwise = a `uncheckedShiftRL#` b
813 -- | Shift the argument left by the specified number of bits
814 -- (which must be non-negative).
815 iShiftL# :: Int# -> Int# -> Int#
816 a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
817 | otherwise = a `uncheckedIShiftL#` b
819 -- | Shift the argument right (signed) by the specified number of bits
820 -- (which must be non-negative).
821 iShiftRA# :: Int# -> Int# -> Int#
822 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
823 | otherwise = a `uncheckedIShiftRA#` b
825 -- | Shift the argument right (unsigned) by the specified number of bits
826 -- (which must be non-negative).
827 iShiftRL# :: Int# -> Int# -> Int#
828 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
829 | otherwise = a `uncheckedIShiftRL#` b
831 #if WORD_SIZE_IN_BITS == 32
833 "narrow32Int#" forall x#. narrow32Int# x# = x#
834 "narrow32Word#" forall x#. narrow32Word# x# = x#
839 "int2Word2Int" forall x#. int2Word# (word2Int# x#) = x#
840 "word2Int2Word" forall x#. word2Int# (int2Word# x#) = x#
845 %********************************************************
847 \subsection{Unpacking C strings}
849 %********************************************************
851 This code is needed for virtually all programs, since it's used for
852 unpacking the strings of error messages.
855 unpackCString# :: Addr# -> [Char]
856 {-# NOINLINE unpackCString# #-}
857 -- There's really no point in inlining this, ever, cos
858 -- the loop doesn't specialise in an interesting
859 -- But it's pretty small, so there's a danger that
860 -- it'll be inlined at every literal, which is a waste
865 | ch `eqChar#` '\0'# = []
866 | otherwise = C# ch : unpack (nh +# 1#)
868 !ch = indexCharOffAddr# addr nh
870 unpackAppendCString# :: Addr# -> [Char] -> [Char]
871 {-# NOINLINE unpackAppendCString# #-}
872 -- See the NOINLINE note on unpackCString#
873 unpackAppendCString# addr rest
877 | ch `eqChar#` '\0'# = rest
878 | otherwise = C# ch : unpack (nh +# 1#)
880 !ch = indexCharOffAddr# addr nh
882 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
884 -- Usually the unpack-list rule turns unpackFoldrCString# into unpackCString#
886 -- It also has a BuiltInRule in PrelRules.lhs:
887 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n)
888 -- = unpackFoldrCString# "foobaz" c n
890 {-# NOINLINE unpackFoldrCString# #-}
891 -- At one stage I had NOINLINE [0] on the grounds that, unlike
892 -- unpackCString#, there *is* some point in inlining
893 -- unpackFoldrCString#, because we get better code for the
894 -- higher-order function call. BUT there may be a lot of
895 -- literal strings, and making a separate 'unpack' loop for
896 -- each is highly gratuitous. See nofib/real/anna/PrettyPrint.
898 unpackFoldrCString# addr f z
902 | ch `eqChar#` '\0'# = z
903 | otherwise = C# ch `f` unpack (nh +# 1#)
905 !ch = indexCharOffAddr# addr nh
907 unpackCStringUtf8# :: Addr# -> [Char]
908 unpackCStringUtf8# addr
912 | ch `eqChar#` '\0'# = []
913 | ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
914 | ch `leChar#` '\xDF'# =
915 C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
916 (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
918 | ch `leChar#` '\xEF'# =
919 C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
920 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
921 (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
924 C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
925 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
926 ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
927 (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
930 !ch = indexCharOffAddr# addr nh
932 unpackNBytes# :: Addr# -> Int# -> [Char]
933 unpackNBytes# _addr 0# = []
934 unpackNBytes# addr len# = unpack [] (len# -# 1#)
939 case indexCharOffAddr# addr i# of
940 ch -> unpack (C# ch : acc) (i# -# 1#)
943 "unpack" [~1] forall a . unpackCString# a = build (unpackFoldrCString# a)
944 "unpack-list" [1] forall a . unpackFoldrCString# a (:) [] = unpackCString# a
945 "unpack-append" forall a n . unpackFoldrCString# a (:) n = unpackAppendCString# a n
947 -- There's a built-in rule (in PrelRules.lhs) for
948 -- unpackFoldr "foo" c (unpackFoldr "baz" c n) = unpackFoldr "foobaz" c n
955 -- | A special argument for the 'Control.Monad.ST.ST' type constructor,
956 -- indexing a state embedded in the 'Prelude.IO' monad by
957 -- 'Control.Monad.ST.stToIO'.