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 {-# OPTIONS_GHC -fno-warn-orphans #-}
67 {-# OPTIONS_HADDOCK hide #-}
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 -----------------------------------------------------------------------------
93 module GHC.Prim, -- Re-export GHC.Prim and GHC.Err, to avoid lots
94 module GHC.Err -- of people having to import it explicitly
104 import {-# SOURCE #-} GHC.Show
105 import {-# SOURCE #-} GHC.Err
106 import {-# SOURCE #-} GHC.IO (failIO)
108 -- These two are not strictly speaking required by this module, but they are
109 -- implicit dependencies whenever () or tuples are mentioned, so adding them
110 -- as imports here helps to get the dependencies right in the new build system.
120 default () -- Double isn't available yet
124 %*********************************************************
126 \subsection{DEBUGGING STUFF}
127 %* (for use when compiling GHC.Base itself doesn't work)
129 %*********************************************************
133 data Bool = False | True
134 data Ordering = LT | EQ | GT
142 (&&) True True = True
148 unpackCString# :: Addr# -> [Char]
149 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
150 unpackAppendCString# :: Addr# -> [Char] -> [Char]
151 unpackCStringUtf8# :: Addr# -> [Char]
152 unpackCString# a = error "urk"
153 unpackFoldrCString# a = error "urk"
154 unpackAppendCString# a = error "urk"
155 unpackCStringUtf8# a = error "urk"
160 %*********************************************************
162 \subsection{Monadic classes @Functor@, @Monad@ }
164 %*********************************************************
167 {- | The 'Functor' class is used for types that can be mapped over.
168 Instances of 'Functor' should satisfy the following laws:
171 > fmap (f . g) == fmap f . fmap g
173 The instances of 'Functor' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
174 defined in the "Prelude" satisfy these laws.
177 class Functor f where
178 fmap :: (a -> b) -> f a -> f b
180 -- | Replace all locations in the input with the same value.
181 -- The default definition is @'fmap' . 'const'@, but this may be
182 -- overridden with a more efficient version.
183 (<$) :: a -> f b -> f a
186 {- | The 'Monad' class defines the basic operations over a /monad/,
187 a concept from a branch of mathematics known as /category theory/.
188 From the perspective of a Haskell programmer, however, it is best to
189 think of a monad as an /abstract datatype/ of actions.
190 Haskell's @do@ expressions provide a convenient syntax for writing
193 Minimal complete definition: '>>=' and 'return'.
195 Instances of 'Monad' should satisfy the following laws:
197 > return a >>= k == k a
199 > m >>= (\x -> k x >>= h) == (m >>= k) >>= h
201 Instances of both 'Monad' and 'Functor' should additionally satisfy the law:
203 > fmap f xs == xs >>= return . f
205 The instances of 'Monad' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
206 defined in the "Prelude" satisfy these laws.
210 -- | Sequentially compose two actions, passing any value produced
211 -- by the first as an argument to the second.
212 (>>=) :: forall a b. m a -> (a -> m b) -> m b
213 -- | Sequentially compose two actions, discarding any value produced
214 -- by the first, like sequencing operators (such as the semicolon)
215 -- in imperative languages.
216 (>>) :: forall a b. m a -> m b -> m b
217 -- Explicit for-alls so that we know what order to
218 -- give type arguments when desugaring
220 -- | Inject a value into the monadic type.
222 -- | Fail with a message. This operation is not part of the
223 -- mathematical definition of a monad, but is invoked on pattern-match
224 -- failure in a @do@ expression.
225 fail :: String -> m a
227 m >> k = m >>= \_ -> k
232 %*********************************************************
234 \subsection{The list type}
236 %*********************************************************
239 -- do explicitly: deriving (Eq, Ord)
240 -- to avoid weird names like con2tag_[]#
242 instance (Eq a) => Eq [a] where
243 {-# SPECIALISE instance Eq [Char] #-}
245 (x:xs) == (y:ys) = x == y && xs == ys
248 instance (Ord a) => Ord [a] where
249 {-# SPECIALISE instance Ord [Char] #-}
251 compare [] (_:_) = LT
252 compare (_:_) [] = GT
253 compare (x:xs) (y:ys) = case compare x y of
257 instance Functor [] where
260 instance Monad [] where
261 m >>= k = foldr ((++) . k) [] m
262 m >> k = foldr ((++) . (\ _ -> k)) [] m
267 A few list functions that appear here because they are used here.
268 The rest of the prelude list functions are in GHC.List.
270 ----------------------------------------------
271 -- foldr/build/augment
272 ----------------------------------------------
275 -- | 'foldr', applied to a binary operator, a starting value (typically
276 -- the right-identity of the operator), and a list, reduces the list
277 -- using the binary operator, from right to left:
279 -- > foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
281 foldr :: (a -> b -> b) -> b -> [a] -> b
283 -- foldr f z (x:xs) = f x (foldr f z xs)
284 {-# INLINE [0] foldr #-}
285 -- Inline only in the final stage, after the foldr/cons rule has had a chance
289 go (y:ys) = y `k` go ys
291 -- | A list producer that can be fused with 'foldr'.
292 -- This function is merely
294 -- > build g = g (:) []
296 -- but GHC's simplifier will transform an expression of the form
297 -- @'foldr' k z ('build' g)@, which may arise after inlining, to @g k z@,
298 -- which avoids producing an intermediate list.
300 build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
301 {-# INLINE [1] build #-}
302 -- The INLINE is important, even though build is tiny,
303 -- because it prevents [] getting inlined in the version that
304 -- appears in the interface file. If [] *is* inlined, it
305 -- won't match with [] appearing in rules in an importing module.
307 -- The "1" says to inline in phase 1
311 -- | A list producer that can be fused with 'foldr'.
312 -- This function is merely
314 -- > augment g xs = g (:) xs
316 -- but GHC's simplifier will transform an expression of the form
317 -- @'foldr' k z ('augment' g xs)@, which may arise after inlining, to
318 -- @g k ('foldr' k z xs)@, which avoids producing an intermediate list.
320 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
321 {-# INLINE [1] augment #-}
322 augment g xs = g (:) xs
325 "fold/build" forall k z (g::forall b. (a->b->b) -> b -> b) .
326 foldr k z (build g) = g k z
328 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) .
329 foldr k z (augment g xs) = g k (foldr k z xs)
331 "foldr/id" foldr (:) [] = \x -> x
332 "foldr/app" [1] forall ys. foldr (:) ys = \xs -> xs ++ ys
333 -- Only activate this from phase 1, because that's
334 -- when we disable the rule that expands (++) into foldr
336 -- The foldr/cons rule looks nice, but it can give disastrously
337 -- bloated code when commpiling
338 -- array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]
339 -- i.e. when there are very very long literal lists
340 -- So I've disabled it for now. We could have special cases
341 -- for short lists, I suppose.
342 -- "foldr/cons" forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)
344 "foldr/single" forall k z x. foldr k z [x] = k x z
345 "foldr/nil" forall k z. foldr k z [] = z
347 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)
348 (h::forall b. (a->b->b) -> b -> b) .
349 augment g (build h) = build (\c n -> g c (h c n))
350 "augment/nil" forall (g::forall b. (a->b->b) -> b -> b) .
351 augment g [] = build g
354 -- This rule is true, but not (I think) useful:
355 -- augment g (augment h t) = augment (\cn -> g c (h c n)) t
359 ----------------------------------------------
361 ----------------------------------------------
364 -- | 'map' @f xs@ is the list obtained by applying @f@ to each element
367 -- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
368 -- > map f [x1, x2, ...] == [f x1, f x2, ...]
370 map :: (a -> b) -> [a] -> [b]
372 map f (x:xs) = f x : map f xs
375 mapFB :: (elt -> lst -> lst) -> (a -> elt) -> a -> lst -> lst
376 {-# INLINE [0] mapFB #-}
377 mapFB c f x ys = c (f x) ys
379 -- The rules for map work like this.
381 -- Up to (but not including) phase 1, we use the "map" rule to
382 -- rewrite all saturated applications of map with its build/fold
383 -- form, hoping for fusion to happen.
384 -- In phase 1 and 0, we switch off that rule, inline build, and
385 -- switch on the "mapList" rule, which rewrites the foldr/mapFB
386 -- thing back into plain map.
388 -- It's important that these two rules aren't both active at once
389 -- (along with build's unfolding) else we'd get an infinite loop
390 -- in the rules. Hence the activation control below.
392 -- The "mapFB" rule optimises compositions of map.
394 -- This same pattern is followed by many other functions:
395 -- e.g. append, filter, iterate, repeat, etc.
398 "map" [~1] forall f xs. map f xs = build (\c n -> foldr (mapFB c f) n xs)
399 "mapList" [1] forall f. foldr (mapFB (:) f) [] = map f
400 "mapFB" forall c f g. mapFB (mapFB c f) g = mapFB c (f.g)
405 ----------------------------------------------
407 ----------------------------------------------
409 -- | Append two lists, i.e.,
411 -- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
412 -- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
414 -- If the first list is not finite, the result is the first list.
416 (++) :: [a] -> [a] -> [a]
418 (++) (x:xs) ys = x : xs ++ ys
421 "++" [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys
427 %*********************************************************
429 \subsection{Type @Bool@}
431 %*********************************************************
434 -- |The 'Bool' type is an enumeration. It is defined with 'False'
435 -- first so that the corresponding 'Prelude.Enum' instance will give
436 -- 'Prelude.fromEnum' 'False' the value zero, and
437 -- 'Prelude.fromEnum' 'True' the value 1.
438 -- The actual definition is in the ghc-prim package.
440 -- XXX These don't work:
441 -- deriving instance Eq Bool
442 -- deriving instance Ord Bool
443 -- <wired into compiler>:
444 -- Illegal binding of built-in syntax: con2tag_Bool#
446 instance Eq Bool where
448 False == False = True
451 instance Ord Bool where
452 compare False True = LT
453 compare True False = GT
456 -- Read is in GHC.Read, Show in GHC.Show
458 -- |'otherwise' is defined as the value 'True'. It helps to make
459 -- guards more readable. eg.
461 -- > f x | x < 0 = ...
462 -- > | otherwise = ...
467 %*********************************************************
469 \subsection{Type @Ordering@}
471 %*********************************************************
474 -- | Represents an ordering relationship between two values: less
475 -- than, equal to, or greater than. An 'Ordering' is returned by
477 -- XXX These don't work:
478 -- deriving instance Eq Ordering
479 -- deriving instance Ord Ordering
480 -- Illegal binding of built-in syntax: con2tag_Ordering#
481 instance Eq Ordering where
486 -- Read in GHC.Read, Show in GHC.Show
488 instance Ord Ordering where
497 %*********************************************************
499 \subsection{Type @Char@ and @String@}
501 %*********************************************************
504 -- | A 'String' is a list of characters. String constants in Haskell are values
509 {-| The character type 'Char' is an enumeration whose values represent
510 Unicode (or equivalently ISO\/IEC 10646) characters
511 (see <http://www.unicode.org/> for details).
512 This set extends the ISO 8859-1 (Latin-1) character set
513 (the first 256 charachers), which is itself an extension of the ASCII
514 character set (the first 128 characters).
515 A character literal in Haskell has type 'Char'.
517 To convert a 'Char' to or from the corresponding 'Int' value defined
518 by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
519 'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
522 -- We don't use deriving for Eq and Ord, because for Ord the derived
523 -- instance defines only compare, which takes two primops. Then
524 -- '>' uses compare, and therefore takes two primops instead of one.
526 instance Eq Char where
527 (C# c1) == (C# c2) = c1 `eqChar#` c2
528 (C# c1) /= (C# c2) = c1 `neChar#` c2
530 instance Ord Char where
531 (C# c1) > (C# c2) = c1 `gtChar#` c2
532 (C# c1) >= (C# c2) = c1 `geChar#` c2
533 (C# c1) <= (C# c2) = c1 `leChar#` c2
534 (C# c1) < (C# c2) = c1 `ltChar#` c2
537 "x# `eqChar#` x#" forall x#. x# `eqChar#` x# = True
538 "x# `neChar#` x#" forall x#. x# `neChar#` x# = False
539 "x# `gtChar#` x#" forall x#. x# `gtChar#` x# = False
540 "x# `geChar#` x#" forall x#. x# `geChar#` x# = True
541 "x# `leChar#` x#" forall x#. x# `leChar#` x# = True
542 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
545 -- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
548 | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
550 = error ("Prelude.chr: bad argument: " ++ showSignedInt (I# 9#) i "")
552 unsafeChr :: Int -> Char
553 unsafeChr (I# i#) = C# (chr# i#)
555 -- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
557 ord (C# c#) = I# (ord# c#)
560 String equality is used when desugaring pattern-matches against strings.
563 eqString :: String -> String -> Bool
564 eqString [] [] = True
565 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
568 {-# RULES "eqString" (==) = eqString #-}
569 -- eqString also has a BuiltInRule in PrelRules.lhs:
570 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
574 %*********************************************************
576 \subsection{Type @Int@}
578 %*********************************************************
581 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
586 {- Seems clumsy. Should perhaps put minInt and MaxInt directly into MachDeps.h -}
587 #if WORD_SIZE_IN_BITS == 31
588 minInt = I# (-0x40000000#)
589 maxInt = I# 0x3FFFFFFF#
590 #elif WORD_SIZE_IN_BITS == 32
591 minInt = I# (-0x80000000#)
592 maxInt = I# 0x7FFFFFFF#
594 minInt = I# (-0x8000000000000000#)
595 maxInt = I# 0x7FFFFFFFFFFFFFFF#
598 instance Eq Int where
602 instance Ord Int where
609 compareInt :: Int -> Int -> Ordering
610 (I# x#) `compareInt` (I# y#) = compareInt# x# y#
612 compareInt# :: Int# -> Int# -> Ordering
620 %*********************************************************
622 \subsection{The function type}
624 %*********************************************************
627 -- | Identity function.
631 -- | The call '(lazy e)' means the same as 'e', but 'lazy' has a
632 -- magical strictness property: it is lazy in its first argument,
633 -- even though its semantics is strict.
636 -- Implementation note: its strictness and unfolding are over-ridden
637 -- by the definition in MkId.lhs; in both cases to nothing at all.
638 -- That way, 'lazy' does not get inlined, and the strictness analyser
639 -- sees it as lazy. Then the worker/wrapper phase inlines it.
643 -- | The call '(inline f)' reduces to 'f', but 'inline' has a BuiltInRule
644 -- that tries to inline 'f' (if it has an unfolding) unconditionally
645 -- The 'NOINLINE' pragma arranges that inline only gets inlined (and
646 -- hence eliminated) late in compilation, after the rule has had
647 -- a god chance to fire.
649 {-# NOINLINE[0] inline #-}
652 -- Assertion function. This simply ignores its boolean argument.
653 -- The compiler may rewrite it to @('assertError' line)@.
655 -- | If the first argument evaluates to 'True', then the result is the
656 -- second argument. Otherwise an 'AssertionFailed' exception is raised,
657 -- containing a 'String' with the source file and line number of the
660 -- Assertions can normally be turned on or off with a compiler flag
661 -- (for GHC, assertions are normally on unless optimisation is turned on
662 -- with @-O@ or the @-fignore-asserts@
663 -- option is given). When assertions are turned off, the first
664 -- argument to 'assert' is ignored, and the second argument is
665 -- returned as the result.
667 -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
668 -- but from Template Haskell onwards it's simply
669 -- defined here in Base.lhs
670 assert :: Bool -> a -> a
676 breakpointCond :: Bool -> a -> a
677 breakpointCond _ r = r
679 data Opaque = forall a. O a
681 -- | Constant function.
685 -- | Function composition.
687 (.) :: (b -> c) -> (a -> b) -> a -> c
690 -- | @'flip' f@ takes its (first) two arguments in the reverse order of @f@.
691 flip :: (a -> b -> c) -> b -> a -> c
694 -- | Application operator. This operator is redundant, since ordinary
695 -- application @(f x)@ means the same as @(f '$' x)@. However, '$' has
696 -- low, right-associative binding precedence, so it sometimes allows
697 -- parentheses to be omitted; for example:
699 -- > f $ g $ h x = f (g (h x))
701 -- It is also useful in higher-order situations, such as @'map' ('$' 0) xs@,
702 -- or @'Data.List.zipWith' ('$') fs xs@.
704 ($) :: (a -> b) -> a -> b
707 -- | @'until' p f@ yields the result of applying @f@ until @p@ holds.
708 until :: (a -> Bool) -> (a -> a) -> a -> a
709 until p f x | p x = x
710 | otherwise = until p f (f x)
712 -- | 'asTypeOf' is a type-restricted version of 'const'. It is usually
713 -- used as an infix operator, and its typing forces its first argument
714 -- (which is usually overloaded) to have the same type as the second.
715 asTypeOf :: a -> a -> a
719 %*********************************************************
721 \subsection{@Functor@ and @Monad@ instances for @IO@}
723 %*********************************************************
726 instance Functor IO where
727 fmap f x = x >>= (return . f)
729 instance Monad IO where
730 {-# INLINE return #-}
733 m >> k = m >>= \ _ -> k
736 fail s = GHC.IO.failIO s
738 returnIO :: a -> IO a
739 returnIO x = IO $ \ s -> (# s, x #)
741 bindIO :: IO a -> (a -> IO b) -> IO b
742 bindIO (IO m) k = IO $ \ s -> case m s of (# new_s, a #) -> unIO (k a) new_s
744 thenIO :: IO a -> IO b -> IO b
745 thenIO (IO m) k = IO $ \ s -> case m s of (# new_s, _ #) -> unIO k new_s
747 unIO :: IO a -> (State# RealWorld -> (# State# RealWorld, a #))
751 %*********************************************************
753 \subsection{@getTag@}
755 %*********************************************************
757 Returns the 'tag' of a constructor application; this function is used
758 by the deriving code for Eq, Ord and Enum.
760 The primitive dataToTag# requires an evaluated constructor application
761 as its argument, so we provide getTag as a wrapper that performs the
762 evaluation before calling dataToTag#. We could have dataToTag#
763 evaluate its argument, but we prefer to do it this way because (a)
764 dataToTag# can be an inline primop if it doesn't need to do any
765 evaluation, and (b) we want to expose the evaluation to the
766 simplifier, because it might be possible to eliminate the evaluation
767 in the case when the argument is already known to be evaluated.
770 {-# INLINE getTag #-}
772 getTag x = x `seq` dataToTag# x
775 %*********************************************************
777 \subsection{Numeric primops}
779 %*********************************************************
782 divInt# :: Int# -> Int# -> Int#
784 -- Be careful NOT to overflow if we do any additional arithmetic
785 -- on the arguments... the following previous version of this
786 -- code has problems with overflow:
787 -- | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
788 -- | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
789 | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
790 | (x# <# 0#) && (y# ># 0#) = ((x# +# 1#) `quotInt#` y#) -# 1#
791 | otherwise = x# `quotInt#` y#
793 modInt# :: Int# -> Int# -> Int#
795 | (x# ># 0#) && (y# <# 0#) ||
796 (x# <# 0#) && (y# ># 0#) = if r# /=# 0# then r# +# y# else 0#
799 !r# = x# `remInt#` y#
802 Definitions of the boxed PrimOps; these will be
803 used in the case of partial applications, etc.
812 {-# INLINE plusInt #-}
813 {-# INLINE minusInt #-}
814 {-# INLINE timesInt #-}
815 {-# INLINE quotInt #-}
816 {-# INLINE remInt #-}
817 {-# INLINE negateInt #-}
819 plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt :: Int -> Int -> Int
820 (I# x) `plusInt` (I# y) = I# (x +# y)
821 (I# x) `minusInt` (I# y) = I# (x -# y)
822 (I# x) `timesInt` (I# y) = I# (x *# y)
823 (I# x) `quotInt` (I# y) = I# (x `quotInt#` y)
824 (I# x) `remInt` (I# y) = I# (x `remInt#` y)
825 (I# x) `divInt` (I# y) = I# (x `divInt#` y)
826 (I# x) `modInt` (I# y) = I# (x `modInt#` y)
829 "x# +# 0#" forall x#. x# +# 0# = x#
830 "0# +# x#" forall x#. 0# +# x# = x#
831 "x# -# 0#" forall x#. x# -# 0# = x#
832 "x# -# x#" forall x#. x# -# x# = 0#
833 "x# *# 0#" forall x#. x# *# 0# = 0#
834 "0# *# x#" forall x#. 0# *# x# = 0#
835 "x# *# 1#" forall x#. x# *# 1# = x#
836 "1# *# x#" forall x#. 1# *# x# = x#
839 negateInt :: Int -> Int
840 negateInt (I# x) = I# (negateInt# x)
842 gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
843 (I# x) `gtInt` (I# y) = x ># y
844 (I# x) `geInt` (I# y) = x >=# y
845 (I# x) `eqInt` (I# y) = x ==# y
846 (I# x) `neInt` (I# y) = x /=# y
847 (I# x) `ltInt` (I# y) = x <# y
848 (I# x) `leInt` (I# y) = x <=# y
851 "x# ># x#" forall x#. x# ># x# = False
852 "x# >=# x#" forall x#. x# >=# x# = True
853 "x# ==# x#" forall x#. x# ==# x# = True
854 "x# /=# x#" forall x#. x# /=# x# = False
855 "x# <# x#" forall x#. x# <# x# = False
856 "x# <=# x#" forall x#. x# <=# x# = True
860 "plusFloat x 0.0" forall x#. plusFloat# x# 0.0# = x#
861 "plusFloat 0.0 x" forall x#. plusFloat# 0.0# x# = x#
862 "minusFloat x 0.0" forall x#. minusFloat# x# 0.0# = x#
863 "minusFloat x x" forall x#. minusFloat# x# x# = 0.0#
864 "timesFloat x 0.0" forall x#. timesFloat# x# 0.0# = 0.0#
865 "timesFloat0.0 x" forall x#. timesFloat# 0.0# x# = 0.0#
866 "timesFloat x 1.0" forall x#. timesFloat# x# 1.0# = x#
867 "timesFloat 1.0 x" forall x#. timesFloat# 1.0# x# = x#
868 "divideFloat x 1.0" forall x#. divideFloat# x# 1.0# = x#
872 "plusDouble x 0.0" forall x#. (+##) x# 0.0## = x#
873 "plusDouble 0.0 x" forall x#. (+##) 0.0## x# = x#
874 "minusDouble x 0.0" forall x#. (-##) x# 0.0## = x#
875 "timesDouble x 1.0" forall x#. (*##) x# 1.0## = x#
876 "timesDouble 1.0 x" forall x#. (*##) 1.0## x# = x#
877 "divideDouble x 1.0" forall x#. (/##) x# 1.0## = x#
881 We'd like to have more rules, but for example:
883 This gives wrong answer (0) for NaN - NaN (should be NaN):
884 "minusDouble x x" forall x#. (-##) x# x# = 0.0##
886 This gives wrong answer (0) for 0 * NaN (should be NaN):
887 "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
889 This gives wrong answer (0) for NaN * 0 (should be NaN):
890 "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
892 These are tested by num014.
895 -- Wrappers for the shift operations. The uncheckedShift# family are
896 -- undefined when the amount being shifted by is greater than the size
897 -- in bits of Int#, so these wrappers perform a check and return
898 -- either zero or -1 appropriately.
900 -- Note that these wrappers still produce undefined results when the
901 -- second argument (the shift amount) is negative.
903 -- | Shift the argument left by the specified number of bits
904 -- (which must be non-negative).
905 shiftL# :: Word# -> Int# -> Word#
906 a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
907 | otherwise = a `uncheckedShiftL#` b
909 -- | Shift the argument right by the specified number of bits
910 -- (which must be non-negative).
911 shiftRL# :: Word# -> Int# -> Word#
912 a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
913 | otherwise = a `uncheckedShiftRL#` b
915 -- | Shift the argument left by the specified number of bits
916 -- (which must be non-negative).
917 iShiftL# :: Int# -> Int# -> Int#
918 a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
919 | otherwise = a `uncheckedIShiftL#` b
921 -- | Shift the argument right (signed) by the specified number of bits
922 -- (which must be non-negative).
923 iShiftRA# :: Int# -> Int# -> Int#
924 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
925 | otherwise = a `uncheckedIShiftRA#` b
927 -- | Shift the argument right (unsigned) by the specified number of bits
928 -- (which must be non-negative).
929 iShiftRL# :: Int# -> Int# -> Int#
930 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
931 | otherwise = a `uncheckedIShiftRL#` b
933 #if WORD_SIZE_IN_BITS == 32
935 "narrow32Int#" forall x#. narrow32Int# x# = x#
936 "narrow32Word#" forall x#. narrow32Word# x# = x#
941 "int2Word2Int" forall x#. int2Word# (word2Int# x#) = x#
942 "word2Int2Word" forall x#. word2Int# (int2Word# x#) = x#
947 %********************************************************
949 \subsection{Unpacking C strings}
951 %********************************************************
953 This code is needed for virtually all programs, since it's used for
954 unpacking the strings of error messages.
957 unpackCString# :: Addr# -> [Char]
958 {-# NOINLINE unpackCString# #-}
959 -- There's really no point in inlining this, ever, cos
960 -- the loop doesn't specialise in an interesting
961 -- But it's pretty small, so there's a danger that
962 -- it'll be inlined at every literal, which is a waste
967 | ch `eqChar#` '\0'# = []
968 | otherwise = C# ch : unpack (nh +# 1#)
970 !ch = indexCharOffAddr# addr nh
972 unpackAppendCString# :: Addr# -> [Char] -> [Char]
973 {-# NOINLINE unpackAppendCString# #-}
974 -- See the NOINLINE note on unpackCString#
975 unpackAppendCString# addr rest
979 | ch `eqChar#` '\0'# = rest
980 | otherwise = C# ch : unpack (nh +# 1#)
982 !ch = indexCharOffAddr# addr nh
984 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
985 {-# NOINLINE [0] unpackFoldrCString# #-}
986 -- Unlike unpackCString#, there *is* some point in inlining unpackFoldrCString#,
987 -- because we get better code for the function call.
988 -- However, don't inline till right at the end;
989 -- usually the unpack-list rule turns it into unpackCStringList
990 -- It also has a BuiltInRule in PrelRules.lhs:
991 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n)
992 -- = unpackFoldrCString# "foobaz" c n
993 unpackFoldrCString# addr f z
997 | ch `eqChar#` '\0'# = z
998 | otherwise = C# ch `f` unpack (nh +# 1#)
1000 !ch = indexCharOffAddr# addr nh
1002 unpackCStringUtf8# :: Addr# -> [Char]
1003 unpackCStringUtf8# addr
1007 | ch `eqChar#` '\0'# = []
1008 | ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
1009 | ch `leChar#` '\xDF'# =
1010 C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
1011 (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
1013 | ch `leChar#` '\xEF'# =
1014 C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
1015 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
1016 (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
1019 C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
1020 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
1021 ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
1022 (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
1025 !ch = indexCharOffAddr# addr nh
1027 unpackNBytes# :: Addr# -> Int# -> [Char]
1028 unpackNBytes# _addr 0# = []
1029 unpackNBytes# addr len# = unpack [] (len# -# 1#)
1034 case indexCharOffAddr# addr i# of
1035 ch -> unpack (C# ch : acc) (i# -# 1#)
1038 "unpack" [~1] forall a . unpackCString# a = build (unpackFoldrCString# a)
1039 "unpack-list" [1] forall a . unpackFoldrCString# a (:) [] = unpackCString# a
1040 "unpack-append" forall a n . unpackFoldrCString# a (:) n = unpackAppendCString# a n
1042 -- There's a built-in rule (in PrelRules.lhs) for
1043 -- unpackFoldr "foo" c (unpackFoldr "baz" c n) = unpackFoldr "foobaz" c n
1050 -- | A special argument for the 'Control.Monad.ST.ST' type constructor,
1051 -- indexing a state embedded in the 'Prelude.IO' monad by
1052 -- 'Control.Monad.ST.stToIO'.