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.Err
111 default () -- Double isn't available yet
115 %*********************************************************
117 \subsection{DEBUGGING STUFF}
118 %* (for use when compiling GHC.Base itself doesn't work)
120 %*********************************************************
124 data Bool = False | True
125 data Ordering = LT | EQ | GT
133 (&&) True True = True
139 unpackCString# :: Addr# -> [Char]
140 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
141 unpackAppendCString# :: Addr# -> [Char] -> [Char]
142 unpackCStringUtf8# :: Addr# -> [Char]
143 unpackCString# a = error "urk"
144 unpackFoldrCString# a = error "urk"
145 unpackAppendCString# a = error "urk"
146 unpackCStringUtf8# a = error "urk"
151 %*********************************************************
153 \subsection{Monadic classes @Functor@, @Monad@ }
155 %*********************************************************
158 {- | The 'Functor' class is used for types that can be mapped over.
159 Instances of 'Functor' should satisfy the following laws:
162 > fmap (f . g) == fmap f . fmap g
164 The instances of 'Functor' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
165 defined in the "Prelude" satisfy these laws.
168 class Functor f where
169 fmap :: (a -> b) -> f a -> f b
171 {- | The 'Monad' class defines the basic operations over a /monad/,
172 a concept from a branch of mathematics known as /category theory/.
173 From the perspective of a Haskell programmer, however, it is best to
174 think of a monad as an /abstract datatype/ of actions.
175 Haskell's @do@ expressions provide a convenient syntax for writing
178 Minimal complete definition: '>>=' and 'return'.
180 Instances of 'Monad' should satisfy the following laws:
182 > return a >>= k == k a
184 > m >>= (\x -> k x >>= h) == (m >>= k) >>= h
186 Instances of both 'Monad' and 'Functor' should additionally satisfy the law:
188 > fmap f xs == xs >>= return . f
190 The instances of 'Monad' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
191 defined in the "Prelude" satisfy these laws.
195 -- | Sequentially compose two actions, passing any value produced
196 -- by the first as an argument to the second.
197 (>>=) :: forall a b. m a -> (a -> m b) -> m b
198 -- | Sequentially compose two actions, discarding any value produced
199 -- by the first, like sequencing operators (such as the semicolon)
200 -- in imperative languages.
201 (>>) :: forall a b. m a -> m b -> m b
202 -- Explicit for-alls so that we know what order to
203 -- give type arguments when desugaring
205 -- | Inject a value into the monadic type.
207 -- | Fail with a message. This operation is not part of the
208 -- mathematical definition of a monad, but is invoked on pattern-match
209 -- failure in a @do@ expression.
210 fail :: String -> m a
212 m >> k = m >>= \_ -> k
217 %*********************************************************
219 \subsection{The list type}
221 %*********************************************************
224 -- do explicitly: deriving (Eq, Ord)
225 -- to avoid weird names like con2tag_[]#
227 instance (Eq a) => Eq [a] where
228 {-# SPECIALISE instance Eq [Char] #-}
230 (x:xs) == (y:ys) = x == y && xs == ys
233 instance (Ord a) => Ord [a] where
234 {-# SPECIALISE instance Ord [Char] #-}
236 compare [] (_:_) = LT
237 compare (_:_) [] = GT
238 compare (x:xs) (y:ys) = case compare x y of
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
274 go (y:ys) = y `k` go ys
276 -- | A list producer that can be fused with 'foldr'.
277 -- This function is merely
279 -- > build g = g (:) []
281 -- but GHC's simplifier will transform an expression of the form
282 -- @'foldr' k z ('build' g)@, which may arise after inlining, to @g k z@,
283 -- which avoids producing an intermediate list.
285 build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
286 {-# INLINE [1] build #-}
287 -- The INLINE is important, even though build is tiny,
288 -- because it prevents [] getting inlined in the version that
289 -- appears in the interface file. If [] *is* inlined, it
290 -- won't match with [] appearing in rules in an importing module.
292 -- The "1" says to inline in phase 1
296 -- | A list producer that can be fused with 'foldr'.
297 -- This function is merely
299 -- > augment g xs = g (:) xs
301 -- but GHC's simplifier will transform an expression of the form
302 -- @'foldr' k z ('augment' g xs)@, which may arise after inlining, to
303 -- @g k ('foldr' k z xs)@, which avoids producing an intermediate list.
305 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
306 {-# INLINE [1] augment #-}
307 augment g xs = g (:) xs
310 "fold/build" forall k z (g::forall b. (a->b->b) -> b -> b) .
311 foldr k z (build g) = g k z
313 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) .
314 foldr k z (augment g xs) = g k (foldr k z xs)
316 "foldr/id" foldr (:) [] = \x -> x
317 "foldr/app" [1] forall ys. foldr (:) ys = \xs -> xs ++ ys
318 -- Only activate this from phase 1, because that's
319 -- when we disable the rule that expands (++) into foldr
321 -- The foldr/cons rule looks nice, but it can give disastrously
322 -- bloated code when commpiling
323 -- array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]
324 -- i.e. when there are very very long literal lists
325 -- So I've disabled it for now. We could have special cases
326 -- for short lists, I suppose.
327 -- "foldr/cons" forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)
329 "foldr/single" forall k z x. foldr k z [x] = k x z
330 "foldr/nil" forall k z. foldr k z [] = z
332 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)
333 (h::forall b. (a->b->b) -> b -> b) .
334 augment g (build h) = build (\c n -> g c (h c n))
335 "augment/nil" forall (g::forall b. (a->b->b) -> b -> b) .
336 augment g [] = build g
339 -- This rule is true, but not (I think) useful:
340 -- augment g (augment h t) = augment (\cn -> g c (h c n)) t
344 ----------------------------------------------
346 ----------------------------------------------
349 -- | 'map' @f xs@ is the list obtained by applying @f@ to each element
352 -- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
353 -- > map f [x1, x2, ...] == [f x1, f x2, ...]
355 map :: (a -> b) -> [a] -> [b]
357 map f (x:xs) = f x : map f xs
360 mapFB :: (elt -> lst -> lst) -> (a -> elt) -> a -> lst -> lst
361 {-# INLINE [0] mapFB #-}
362 mapFB c f x ys = c (f x) ys
364 -- The rules for map work like this.
366 -- Up to (but not including) phase 1, we use the "map" rule to
367 -- rewrite all saturated applications of map with its build/fold
368 -- form, hoping for fusion to happen.
369 -- In phase 1 and 0, we switch off that rule, inline build, and
370 -- switch on the "mapList" rule, which rewrites the foldr/mapFB
371 -- thing back into plain map.
373 -- It's important that these two rules aren't both active at once
374 -- (along with build's unfolding) else we'd get an infinite loop
375 -- in the rules. Hence the activation control below.
377 -- The "mapFB" rule optimises compositions of map.
379 -- This same pattern is followed by many other functions:
380 -- e.g. append, filter, iterate, repeat, etc.
383 "map" [~1] forall f xs. map f xs = build (\c n -> foldr (mapFB c f) n xs)
384 "mapList" [1] forall f. foldr (mapFB (:) f) [] = map f
385 "mapFB" forall c f g. mapFB (mapFB c f) g = mapFB c (f.g)
390 ----------------------------------------------
392 ----------------------------------------------
394 -- | Append two lists, i.e.,
396 -- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
397 -- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
399 -- If the first list is not finite, the result is the first list.
401 (++) :: [a] -> [a] -> [a]
403 (++) (x:xs) ys = x : xs ++ ys
406 "++" [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys
412 %*********************************************************
414 \subsection{Type @Bool@}
416 %*********************************************************
419 -- |The 'Bool' type is an enumeration. It is defined with 'False'
420 -- first so that the corresponding 'Prelude.Enum' instance will give
421 -- 'Prelude.fromEnum' 'False' the value zero, and
422 -- 'Prelude.fromEnum' 'True' the value 1.
423 -- The actual definition is in the ghc-prim package.
425 -- XXX These don't work:
426 -- deriving instance Eq Bool
427 -- deriving instance Ord Bool
428 -- <wired into compiler>:
429 -- Illegal binding of built-in syntax: con2tag_Bool#
431 instance Eq Bool where
433 False == False = True
436 instance Ord Bool where
437 compare False True = LT
438 compare True False = GT
441 -- Read is in GHC.Read, Show in GHC.Show
443 -- |'otherwise' is defined as the value 'True'. It helps to make
444 -- guards more readable. eg.
446 -- > f x | x < 0 = ...
447 -- > | otherwise = ...
452 %*********************************************************
454 \subsection{Type @Ordering@}
456 %*********************************************************
459 -- | Represents an ordering relationship between two values: less
460 -- than, equal to, or greater than. An 'Ordering' is returned by
462 -- XXX These don't work:
463 -- deriving instance Eq Ordering
464 -- deriving instance Ord Ordering
465 -- Illegal binding of built-in syntax: con2tag_Ordering#
466 instance Eq Ordering where
471 -- Read in GHC.Read, Show in GHC.Show
473 instance Ord Ordering where
482 %*********************************************************
484 \subsection{Type @Char@ and @String@}
486 %*********************************************************
489 -- | A 'String' is a list of characters. String constants in Haskell are values
494 {-| The character type 'Char' is an enumeration whose values represent
495 Unicode (or equivalently ISO\/IEC 10646) characters
496 (see <http://www.unicode.org/> for details).
497 This set extends the ISO 8859-1 (Latin-1) character set
498 (the first 256 charachers), which is itself an extension of the ASCII
499 character set (the first 128 characters).
500 A character literal in Haskell has type 'Char'.
502 To convert a 'Char' to or from the corresponding 'Int' value defined
503 by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
504 'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
507 -- We don't use deriving for Eq and Ord, because for Ord the derived
508 -- instance defines only compare, which takes two primops. Then
509 -- '>' uses compare, and therefore takes two primops instead of one.
511 instance Eq Char where
512 (C# c1) == (C# c2) = c1 `eqChar#` c2
513 (C# c1) /= (C# c2) = c1 `neChar#` c2
515 instance Ord Char where
516 (C# c1) > (C# c2) = c1 `gtChar#` c2
517 (C# c1) >= (C# c2) = c1 `geChar#` c2
518 (C# c1) <= (C# c2) = c1 `leChar#` c2
519 (C# c1) < (C# c2) = c1 `ltChar#` c2
522 "x# `eqChar#` x#" forall x#. x# `eqChar#` x# = True
523 "x# `neChar#` x#" forall x#. x# `neChar#` x# = False
524 "x# `gtChar#` x#" forall x#. x# `gtChar#` x# = False
525 "x# `geChar#` x#" forall x#. x# `geChar#` x# = True
526 "x# `leChar#` x#" forall x#. x# `leChar#` x# = True
527 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
530 -- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
532 chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
533 | otherwise = error "Prelude.chr: bad argument"
535 unsafeChr :: Int -> Char
536 unsafeChr (I# i#) = C# (chr# i#)
538 -- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
540 ord (C# c#) = I# (ord# c#)
543 String equality is used when desugaring pattern-matches against strings.
546 eqString :: String -> String -> Bool
547 eqString [] [] = True
548 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
551 {-# RULES "eqString" (==) = eqString #-}
552 -- eqString also has a BuiltInRule in PrelRules.lhs:
553 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
557 %*********************************************************
559 \subsection{Type @Int@}
561 %*********************************************************
564 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
569 {- Seems clumsy. Should perhaps put minInt and MaxInt directly into MachDeps.h -}
570 #if WORD_SIZE_IN_BITS == 31
571 minInt = I# (-0x40000000#)
572 maxInt = I# 0x3FFFFFFF#
573 #elif WORD_SIZE_IN_BITS == 32
574 minInt = I# (-0x80000000#)
575 maxInt = I# 0x7FFFFFFF#
577 minInt = I# (-0x8000000000000000#)
578 maxInt = I# 0x7FFFFFFFFFFFFFFF#
581 instance Eq Int where
585 instance Ord Int where
592 compareInt :: Int -> Int -> Ordering
593 (I# x#) `compareInt` (I# y#) = compareInt# x# y#
595 compareInt# :: Int# -> Int# -> Ordering
603 %*********************************************************
605 \subsection{The function type}
607 %*********************************************************
610 -- | Identity function.
614 -- | The call '(lazy e)' means the same as 'e', but 'lazy' has a
615 -- magical strictness property: it is lazy in its first argument,
616 -- even though its semantics is strict.
619 -- Implementation note: its strictness and unfolding are over-ridden
620 -- by the definition in MkId.lhs; in both cases to nothing at all.
621 -- That way, 'lazy' does not get inlined, and the strictness analyser
622 -- sees it as lazy. Then the worker/wrapper phase inlines it.
626 -- | The call '(inline f)' reduces to 'f', but 'inline' has a BuiltInRule
627 -- that tries to inline 'f' (if it has an unfolding) unconditionally
628 -- The 'NOINLINE' pragma arranges that inline only gets inlined (and
629 -- hence eliminated) late in compilation, after the rule has had
630 -- a god chance to fire.
632 {-# NOINLINE[0] inline #-}
635 -- Assertion function. This simply ignores its boolean argument.
636 -- The compiler may rewrite it to @('assertError' line)@.
638 -- | If the first argument evaluates to 'True', then the result is the
639 -- second argument. Otherwise an 'AssertionFailed' exception is raised,
640 -- containing a 'String' with the source file and line number of the
643 -- Assertions can normally be turned on or off with a compiler flag
644 -- (for GHC, assertions are normally on unless optimisation is turned on
645 -- with @-O@ or the @-fignore-asserts@
646 -- option is given). When assertions are turned off, the first
647 -- argument to 'assert' is ignored, and the second argument is
648 -- returned as the result.
650 -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
651 -- but from Template Haskell onwards it's simply
652 -- defined here in Base.lhs
653 assert :: Bool -> a -> a
659 breakpointCond :: Bool -> a -> a
660 breakpointCond _ r = r
662 data Opaque = forall a. O a
664 -- | Constant function.
668 -- | Function composition.
670 (.) :: (b -> c) -> (a -> b) -> a -> c
673 -- | @'flip' f@ takes its (first) two arguments in the reverse order of @f@.
674 flip :: (a -> b -> c) -> b -> a -> c
677 -- | Application operator. This operator is redundant, since ordinary
678 -- application @(f x)@ means the same as @(f '$' x)@. However, '$' has
679 -- low, right-associative binding precedence, so it sometimes allows
680 -- parentheses to be omitted; for example:
682 -- > f $ g $ h x = f (g (h x))
684 -- It is also useful in higher-order situations, such as @'map' ('$' 0) xs@,
685 -- or @'Data.List.zipWith' ('$') fs xs@.
687 ($) :: (a -> b) -> a -> b
690 -- | @'until' p f@ yields the result of applying @f@ until @p@ holds.
691 until :: (a -> Bool) -> (a -> a) -> a -> a
692 until p f x | p x = x
693 | otherwise = until p f (f x)
695 -- | 'asTypeOf' is a type-restricted version of 'const'. It is usually
696 -- used as an infix operator, and its typing forces its first argument
697 -- (which is usually overloaded) to have the same type as the second.
698 asTypeOf :: a -> a -> a
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 "timesDouble x 1.0" forall x#. (*##) x# 1.0## = x#
838 "timesDouble 1.0 x" forall x#. (*##) 1.0## x# = x#
839 "divideDouble x 1.0" forall x#. (/##) x# 1.0## = x#
843 We'd like to have more rules, but for example:
845 This gives wrong answer (0) for NaN - NaN (should be NaN):
846 "minusDouble x x" forall x#. (-##) x# x# = 0.0##
848 This gives wrong answer (0) for 0 * NaN (should be NaN):
849 "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
851 This gives wrong answer (0) for NaN * 0 (should be NaN):
852 "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
854 These are tested by num014.
857 -- Wrappers for the shift operations. The uncheckedShift# family are
858 -- undefined when the amount being shifted by is greater than the size
859 -- in bits of Int#, so these wrappers perform a check and return
860 -- either zero or -1 appropriately.
862 -- Note that these wrappers still produce undefined results when the
863 -- second argument (the shift amount) is negative.
865 -- | Shift the argument left by the specified number of bits
866 -- (which must be non-negative).
867 shiftL# :: Word# -> Int# -> Word#
868 a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
869 | otherwise = a `uncheckedShiftL#` b
871 -- | Shift the argument right by the specified number of bits
872 -- (which must be non-negative).
873 shiftRL# :: Word# -> Int# -> Word#
874 a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
875 | otherwise = a `uncheckedShiftRL#` b
877 -- | Shift the argument left by the specified number of bits
878 -- (which must be non-negative).
879 iShiftL# :: Int# -> Int# -> Int#
880 a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
881 | otherwise = a `uncheckedIShiftL#` b
883 -- | Shift the argument right (signed) by the specified number of bits
884 -- (which must be non-negative).
885 iShiftRA# :: Int# -> Int# -> Int#
886 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
887 | otherwise = a `uncheckedIShiftRA#` b
889 -- | Shift the argument right (unsigned) by the specified number of bits
890 -- (which must be non-negative).
891 iShiftRL# :: Int# -> Int# -> Int#
892 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
893 | otherwise = a `uncheckedIShiftRL#` b
895 #if WORD_SIZE_IN_BITS == 32
897 "narrow32Int#" forall x#. narrow32Int# x# = x#
898 "narrow32Word#" forall x#. narrow32Word# x# = x#
903 "int2Word2Int" forall x#. int2Word# (word2Int# x#) = x#
904 "word2Int2Word" forall x#. word2Int# (int2Word# x#) = x#
909 %********************************************************
911 \subsection{Unpacking C strings}
913 %********************************************************
915 This code is needed for virtually all programs, since it's used for
916 unpacking the strings of error messages.
919 unpackCString# :: Addr# -> [Char]
920 {-# NOINLINE [1] unpackCString# #-}
925 | ch `eqChar#` '\0'# = []
926 | otherwise = C# ch : unpack (nh +# 1#)
928 ch = indexCharOffAddr# addr nh
930 unpackAppendCString# :: Addr# -> [Char] -> [Char]
931 unpackAppendCString# addr rest
935 | ch `eqChar#` '\0'# = rest
936 | otherwise = C# ch : unpack (nh +# 1#)
938 ch = indexCharOffAddr# addr nh
940 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
941 {-# NOINLINE [0] unpackFoldrCString# #-}
942 -- Don't inline till right at the end;
943 -- usually the unpack-list rule turns it into unpackCStringList
944 -- It also has a BuiltInRule in PrelRules.lhs:
945 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n)
946 -- = unpackFoldrCString# "foobaz" c n
947 unpackFoldrCString# addr f z
951 | ch `eqChar#` '\0'# = z
952 | otherwise = C# ch `f` unpack (nh +# 1#)
954 ch = indexCharOffAddr# addr nh
956 unpackCStringUtf8# :: Addr# -> [Char]
957 unpackCStringUtf8# addr
961 | ch `eqChar#` '\0'# = []
962 | ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
963 | ch `leChar#` '\xDF'# =
964 C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
965 (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
967 | ch `leChar#` '\xEF'# =
968 C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
969 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
970 (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
973 C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
974 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
975 ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
976 (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
979 ch = indexCharOffAddr# addr nh
981 unpackNBytes# :: Addr# -> Int# -> [Char]
982 unpackNBytes# _addr 0# = []
983 unpackNBytes# addr len# = unpack [] (len# -# 1#)
988 case indexCharOffAddr# addr i# of
989 ch -> unpack (C# ch : acc) (i# -# 1#)
992 "unpack" [~1] forall a . unpackCString# a = build (unpackFoldrCString# a)
993 "unpack-list" [1] forall a . unpackFoldrCString# a (:) [] = unpackCString# a
994 "unpack-append" forall a n . unpackFoldrCString# a (:) n = unpackAppendCString# a n
996 -- There's a built-in rule (in PrelRules.lhs) for
997 -- unpackFoldr "foo" c (unpackFoldr "baz" c n) = unpackFoldr "foobaz" c n
1004 -- | A special argument for the 'Control.Monad.ST.ST' type constructor,
1005 -- indexing a state embedded in the 'Prelude.IO' monad by
1006 -- 'Control.Monad.ST.stToIO'.