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 ----------------------------------------------
259 Note [Inlining for foldr]
260 ~~~~~~~~~~~~~~~~~~~~~~~~~
261 Inline foldr only in the final stage (0), after the foldr rules
264 Notice that we write foldr with just *two* arguments so that it'll inline
265 when given just those two arguments. Those are the ones that allow it to
266 be specialised for its argument functions. If you give it *three* args
267 then a definition like
268 unpack = foldr unpk_fn unpk_arg
269 does not get foldr inlined. But now 'unpack' will probably be inlined at
270 every call site (being small and arity 1), and *that* will make foldr inline!
271 So we get a copy of foldr at every call of unpack. This is particularly
272 bad for literal strings.
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 #-} -- See Note [Inlining for foldr]
288 go (y:ys) = y `k` go ys
290 -- | A list producer that can be fused with 'foldr'.
291 -- This function is merely
293 -- > build g = g (:) []
295 -- but GHC's simplifier will transform an expression of the form
296 -- @'foldr' k z ('build' g)@, which may arise after inlining, to @g k z@,
297 -- which avoids producing an intermediate list.
299 build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
300 {-# INLINE [1] build #-}
301 -- The INLINE is important, even though build is tiny,
302 -- because it prevents [] getting inlined in the version that
303 -- appears in the interface file. If [] *is* inlined, it
304 -- won't match with [] appearing in rules in an importing module.
306 -- The "1" says to inline in phase 1
310 -- | A list producer that can be fused with 'foldr'.
311 -- This function is merely
313 -- > augment g xs = g (:) xs
315 -- but GHC's simplifier will transform an expression of the form
316 -- @'foldr' k z ('augment' g xs)@, which may arise after inlining, to
317 -- @g k ('foldr' k z xs)@, which avoids producing an intermediate list.
319 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
320 {-# INLINE [1] augment #-}
321 augment g xs = g (:) xs
324 "fold/build" forall k z (g::forall b. (a->b->b) -> b -> b) .
325 foldr k z (build g) = g k z
327 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) .
328 foldr k z (augment g xs) = g k (foldr k z xs)
330 "foldr/id" foldr (:) [] = \x -> x
331 "foldr/app" [1] forall ys. foldr (:) ys = \xs -> xs ++ ys
332 -- Only activate this from phase 1, because that's
333 -- when we disable the rule that expands (++) into foldr
335 -- The foldr/cons rule looks nice, but it can give disastrously
336 -- bloated code when commpiling
337 -- array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]
338 -- i.e. when there are very very long literal lists
339 -- So I've disabled it for now. We could have special cases
340 -- for short lists, I suppose.
341 -- "foldr/cons" forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)
343 "foldr/single" forall k z x. foldr k z [x] = k x z
344 "foldr/nil" forall k z. foldr k z [] = z
346 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)
347 (h::forall b. (a->b->b) -> b -> b) .
348 augment g (build h) = build (\c n -> g c (h c n))
349 "augment/nil" forall (g::forall b. (a->b->b) -> b -> b) .
350 augment g [] = build g
353 -- This rule is true, but not (I think) useful:
354 -- augment g (augment h t) = augment (\cn -> g c (h c n)) t
358 ----------------------------------------------
360 ----------------------------------------------
363 -- | 'map' @f xs@ is the list obtained by applying @f@ to each element
366 -- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
367 -- > map f [x1, x2, ...] == [f x1, f x2, ...]
369 map :: (a -> b) -> [a] -> [b]
371 map f (x:xs) = f x : map f xs
374 mapFB :: (elt -> lst -> lst) -> (a -> elt) -> a -> lst -> lst
375 {-# INLINE [0] mapFB #-}
376 mapFB c f x ys = c (f x) ys
378 -- The rules for map work like this.
380 -- Up to (but not including) phase 1, we use the "map" rule to
381 -- rewrite all saturated applications of map with its build/fold
382 -- form, hoping for fusion to happen.
383 -- In phase 1 and 0, we switch off that rule, inline build, and
384 -- switch on the "mapList" rule, which rewrites the foldr/mapFB
385 -- thing back into plain map.
387 -- It's important that these two rules aren't both active at once
388 -- (along with build's unfolding) else we'd get an infinite loop
389 -- in the rules. Hence the activation control below.
391 -- The "mapFB" rule optimises compositions of map.
393 -- This same pattern is followed by many other functions:
394 -- e.g. append, filter, iterate, repeat, etc.
397 "map" [~1] forall f xs. map f xs = build (\c n -> foldr (mapFB c f) n xs)
398 "mapList" [1] forall f. foldr (mapFB (:) f) [] = map f
399 "mapFB" forall c f g. mapFB (mapFB c f) g = mapFB c (f.g)
404 ----------------------------------------------
406 ----------------------------------------------
408 -- | Append two lists, i.e.,
410 -- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
411 -- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
413 -- If the first list is not finite, the result is the first list.
415 (++) :: [a] -> [a] -> [a]
417 (++) (x:xs) ys = x : xs ++ ys
420 "++" [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys
426 %*********************************************************
428 \subsection{Type @Bool@}
430 %*********************************************************
433 -- |The 'Bool' type is an enumeration. It is defined with 'False'
434 -- first so that the corresponding 'Prelude.Enum' instance will give
435 -- 'Prelude.fromEnum' 'False' the value zero, and
436 -- 'Prelude.fromEnum' 'True' the value 1.
437 -- The actual definition is in the ghc-prim package.
439 -- XXX These don't work:
440 -- deriving instance Eq Bool
441 -- deriving instance Ord Bool
442 -- <wired into compiler>:
443 -- Illegal binding of built-in syntax: con2tag_Bool#
445 instance Eq Bool where
447 False == False = True
450 instance Ord Bool where
451 compare False True = LT
452 compare True False = GT
455 -- Read is in GHC.Read, Show in GHC.Show
457 -- |'otherwise' is defined as the value 'True'. It helps to make
458 -- guards more readable. eg.
460 -- > f x | x < 0 = ...
461 -- > | otherwise = ...
466 %*********************************************************
468 \subsection{Type @Ordering@}
470 %*********************************************************
473 -- | Represents an ordering relationship between two values: less
474 -- than, equal to, or greater than. An 'Ordering' is returned by
476 -- XXX These don't work:
477 -- deriving instance Eq Ordering
478 -- deriving instance Ord Ordering
479 -- Illegal binding of built-in syntax: con2tag_Ordering#
480 instance Eq Ordering where
485 -- Read in GHC.Read, Show in GHC.Show
487 instance Ord Ordering where
496 %*********************************************************
498 \subsection{Type @Char@ and @String@}
500 %*********************************************************
503 -- | A 'String' is a list of characters. String constants in Haskell are values
508 {-| The character type 'Char' is an enumeration whose values represent
509 Unicode (or equivalently ISO\/IEC 10646) characters
510 (see <http://www.unicode.org/> for details).
511 This set extends the ISO 8859-1 (Latin-1) character set
512 (the first 256 charachers), which is itself an extension of the ASCII
513 character set (the first 128 characters).
514 A character literal in Haskell has type 'Char'.
516 To convert a 'Char' to or from the corresponding 'Int' value defined
517 by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
518 'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
521 -- We don't use deriving for Eq and Ord, because for Ord the derived
522 -- instance defines only compare, which takes two primops. Then
523 -- '>' uses compare, and therefore takes two primops instead of one.
525 instance Eq Char where
526 (C# c1) == (C# c2) = c1 `eqChar#` c2
527 (C# c1) /= (C# c2) = c1 `neChar#` c2
529 instance Ord Char where
530 (C# c1) > (C# c2) = c1 `gtChar#` c2
531 (C# c1) >= (C# c2) = c1 `geChar#` c2
532 (C# c1) <= (C# c2) = c1 `leChar#` c2
533 (C# c1) < (C# c2) = c1 `ltChar#` c2
536 "x# `eqChar#` x#" forall x#. x# `eqChar#` x# = True
537 "x# `neChar#` x#" forall x#. x# `neChar#` x# = False
538 "x# `gtChar#` x#" forall x#. x# `gtChar#` x# = False
539 "x# `geChar#` x#" forall x#. x# `geChar#` x# = True
540 "x# `leChar#` x#" forall x#. x# `leChar#` x# = True
541 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
544 -- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
546 chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
547 | otherwise = error "Prelude.chr: bad argument"
549 unsafeChr :: Int -> Char
550 unsafeChr (I# i#) = C# (chr# i#)
552 -- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
554 ord (C# c#) = I# (ord# c#)
557 String equality is used when desugaring pattern-matches against strings.
560 eqString :: String -> String -> Bool
561 eqString [] [] = True
562 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
565 {-# RULES "eqString" (==) = eqString #-}
566 -- eqString also has a BuiltInRule in PrelRules.lhs:
567 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
571 %*********************************************************
573 \subsection{Type @Int@}
575 %*********************************************************
578 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
583 {- Seems clumsy. Should perhaps put minInt and MaxInt directly into MachDeps.h -}
584 #if WORD_SIZE_IN_BITS == 31
585 minInt = I# (-0x40000000#)
586 maxInt = I# 0x3FFFFFFF#
587 #elif WORD_SIZE_IN_BITS == 32
588 minInt = I# (-0x80000000#)
589 maxInt = I# 0x7FFFFFFF#
591 minInt = I# (-0x8000000000000000#)
592 maxInt = I# 0x7FFFFFFFFFFFFFFF#
595 instance Eq Int where
599 instance Ord Int where
606 compareInt :: Int -> Int -> Ordering
607 (I# x#) `compareInt` (I# y#) = compareInt# x# y#
609 compareInt# :: Int# -> Int# -> Ordering
617 %*********************************************************
619 \subsection{The function type}
621 %*********************************************************
624 -- | Identity function.
628 -- | The call '(lazy e)' means the same as 'e', but 'lazy' has a
629 -- magical strictness property: it is lazy in its first argument,
630 -- even though its semantics is strict.
633 -- Implementation note: its strictness and unfolding are over-ridden
634 -- by the definition in MkId.lhs; in both cases to nothing at all.
635 -- That way, 'lazy' does not get inlined, and the strictness analyser
636 -- sees it as lazy. Then the worker/wrapper phase inlines it.
640 -- | The call '(inline f)' reduces to 'f', but 'inline' has a BuiltInRule
641 -- that tries to inline 'f' (if it has an unfolding) unconditionally
642 -- The 'NOINLINE' pragma arranges that inline only gets inlined (and
643 -- hence eliminated) late in compilation, after the rule has had
644 -- a god chance to fire.
646 {-# NOINLINE[0] inline #-}
649 -- Assertion function. This simply ignores its boolean argument.
650 -- The compiler may rewrite it to @('assertError' line)@.
652 -- | If the first argument evaluates to 'True', then the result is the
653 -- second argument. Otherwise an 'AssertionFailed' exception is raised,
654 -- containing a 'String' with the source file and line number of the
657 -- Assertions can normally be turned on or off with a compiler flag
658 -- (for GHC, assertions are normally on unless optimisation is turned on
659 -- with @-O@ or the @-fignore-asserts@
660 -- option is given). When assertions are turned off, the first
661 -- argument to 'assert' is ignored, and the second argument is
662 -- returned as the result.
664 -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
665 -- but from Template Haskell onwards it's simply
666 -- defined here in Base.lhs
667 assert :: Bool -> a -> a
673 breakpointCond :: Bool -> a -> a
674 breakpointCond _ r = r
676 data Opaque = forall a. O a
678 -- | Constant function.
682 -- | Function composition.
684 (.) :: (b -> c) -> (a -> b) -> a -> c
685 (.) f g = \x -> f (g x)
687 -- | @'flip' f@ takes its (first) two arguments in the reverse order of @f@.
688 flip :: (a -> b -> c) -> b -> a -> c
691 -- | Application operator. This operator is redundant, since ordinary
692 -- application @(f x)@ means the same as @(f '$' x)@. However, '$' has
693 -- low, right-associative binding precedence, so it sometimes allows
694 -- parentheses to be omitted; for example:
696 -- > f $ g $ h x = f (g (h x))
698 -- It is also useful in higher-order situations, such as @'map' ('$' 0) xs@,
699 -- or @'Data.List.zipWith' ('$') fs xs@.
701 ($) :: (a -> b) -> a -> b
704 -- | @'until' p f@ yields the result of applying @f@ until @p@ holds.
705 until :: (a -> Bool) -> (a -> a) -> a -> a
706 until p f x | p x = x
707 | otherwise = until p f (f x)
709 -- | 'asTypeOf' is a type-restricted version of 'const'. It is usually
710 -- used as an infix operator, and its typing forces its first argument
711 -- (which is usually overloaded) to have the same type as the second.
712 asTypeOf :: a -> a -> a
716 %*********************************************************
718 \subsection{@getTag@}
720 %*********************************************************
722 Returns the 'tag' of a constructor application; this function is used
723 by the deriving code for Eq, Ord and Enum.
725 The primitive dataToTag# requires an evaluated constructor application
726 as its argument, so we provide getTag as a wrapper that performs the
727 evaluation before calling dataToTag#. We could have dataToTag#
728 evaluate its argument, but we prefer to do it this way because (a)
729 dataToTag# can be an inline primop if it doesn't need to do any
730 evaluation, and (b) we want to expose the evaluation to the
731 simplifier, because it might be possible to eliminate the evaluation
732 in the case when the argument is already known to be evaluated.
735 {-# INLINE getTag #-}
737 getTag x = x `seq` dataToTag# x
740 %*********************************************************
742 \subsection{Numeric primops}
744 %*********************************************************
747 divInt# :: Int# -> Int# -> Int#
749 -- Be careful NOT to overflow if we do any additional arithmetic
750 -- on the arguments... the following previous version of this
751 -- code has problems with overflow:
752 -- | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
753 -- | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
754 | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
755 | (x# <# 0#) && (y# ># 0#) = ((x# +# 1#) `quotInt#` y#) -# 1#
756 | otherwise = x# `quotInt#` y#
758 modInt# :: Int# -> Int# -> Int#
760 | (x# ># 0#) && (y# <# 0#) ||
761 (x# <# 0#) && (y# ># 0#) = if r# /=# 0# then r# +# y# else 0#
767 Definitions of the boxed PrimOps; these will be
768 used in the case of partial applications, etc.
777 {-# INLINE plusInt #-}
778 {-# INLINE minusInt #-}
779 {-# INLINE timesInt #-}
780 {-# INLINE quotInt #-}
781 {-# INLINE remInt #-}
782 {-# INLINE negateInt #-}
784 plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt, gcdInt :: Int -> Int -> Int
785 (I# x) `plusInt` (I# y) = I# (x +# y)
786 (I# x) `minusInt` (I# y) = I# (x -# y)
787 (I# x) `timesInt` (I# y) = I# (x *# y)
788 (I# x) `quotInt` (I# y) = I# (x `quotInt#` y)
789 (I# x) `remInt` (I# y) = I# (x `remInt#` y)
790 (I# x) `divInt` (I# y) = I# (x `divInt#` y)
791 (I# x) `modInt` (I# y) = I# (x `modInt#` y)
794 "x# +# 0#" forall x#. x# +# 0# = x#
795 "0# +# x#" forall x#. 0# +# x# = x#
796 "x# -# 0#" forall x#. x# -# 0# = x#
797 "x# -# x#" forall x#. x# -# x# = 0#
798 "x# *# 0#" forall x#. x# *# 0# = 0#
799 "0# *# x#" forall x#. 0# *# x# = 0#
800 "x# *# 1#" forall x#. x# *# 1# = x#
801 "1# *# x#" forall x#. 1# *# x# = x#
804 gcdInt (I# a) (I# b) = g a b
805 where g 0# 0# = error "GHC.Base.gcdInt: gcd 0 0 is undefined"
808 g _ _ = I# (gcdInt# absA absB)
810 absInt x = if x <# 0# then negateInt# x else x
815 negateInt :: Int -> Int
816 negateInt (I# x) = I# (negateInt# x)
818 gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
819 (I# x) `gtInt` (I# y) = x ># y
820 (I# x) `geInt` (I# y) = x >=# y
821 (I# x) `eqInt` (I# y) = x ==# y
822 (I# x) `neInt` (I# y) = x /=# y
823 (I# x) `ltInt` (I# y) = x <# y
824 (I# x) `leInt` (I# y) = x <=# y
827 "x# ># x#" forall x#. x# ># x# = False
828 "x# >=# x#" forall x#. x# >=# x# = True
829 "x# ==# x#" forall x#. x# ==# x# = True
830 "x# /=# x#" forall x#. x# /=# x# = False
831 "x# <# x#" forall x#. x# <# x# = False
832 "x# <=# x#" forall x#. x# <=# x# = True
836 "plusFloat x 0.0" forall x#. plusFloat# x# 0.0# = x#
837 "plusFloat 0.0 x" forall x#. plusFloat# 0.0# x# = x#
838 "minusFloat x 0.0" forall x#. minusFloat# x# 0.0# = x#
839 "minusFloat x x" forall x#. minusFloat# x# x# = 0.0#
840 "timesFloat x 0.0" forall x#. timesFloat# x# 0.0# = 0.0#
841 "timesFloat0.0 x" forall x#. timesFloat# 0.0# x# = 0.0#
842 "timesFloat x 1.0" forall x#. timesFloat# x# 1.0# = x#
843 "timesFloat 1.0 x" forall x#. timesFloat# 1.0# x# = x#
844 "divideFloat x 1.0" forall x#. divideFloat# x# 1.0# = x#
848 "plusDouble x 0.0" forall x#. (+##) x# 0.0## = x#
849 "plusDouble 0.0 x" forall x#. (+##) 0.0## x# = x#
850 "minusDouble x 0.0" forall x#. (-##) x# 0.0## = x#
851 "timesDouble x 1.0" forall x#. (*##) x# 1.0## = x#
852 "timesDouble 1.0 x" forall x#. (*##) 1.0## x# = x#
853 "divideDouble x 1.0" forall x#. (/##) x# 1.0## = x#
857 We'd like to have more rules, but for example:
859 This gives wrong answer (0) for NaN - NaN (should be NaN):
860 "minusDouble x x" forall x#. (-##) x# x# = 0.0##
862 This gives wrong answer (0) for 0 * NaN (should be NaN):
863 "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
865 This gives wrong answer (0) for NaN * 0 (should be NaN):
866 "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
868 These are tested by num014.
871 -- Wrappers for the shift operations. The uncheckedShift# family are
872 -- undefined when the amount being shifted by is greater than the size
873 -- in bits of Int#, so these wrappers perform a check and return
874 -- either zero or -1 appropriately.
876 -- Note that these wrappers still produce undefined results when the
877 -- second argument (the shift amount) is negative.
879 -- | Shift the argument left by the specified number of bits
880 -- (which must be non-negative).
881 shiftL# :: Word# -> Int# -> Word#
882 a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
883 | otherwise = a `uncheckedShiftL#` b
885 -- | Shift the argument right by the specified number of bits
886 -- (which must be non-negative).
887 shiftRL# :: Word# -> Int# -> Word#
888 a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
889 | otherwise = a `uncheckedShiftRL#` b
891 -- | Shift the argument left by the specified number of bits
892 -- (which must be non-negative).
893 iShiftL# :: Int# -> Int# -> Int#
894 a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
895 | otherwise = a `uncheckedIShiftL#` b
897 -- | Shift the argument right (signed) by the specified number of bits
898 -- (which must be non-negative).
899 iShiftRA# :: Int# -> Int# -> Int#
900 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
901 | otherwise = a `uncheckedIShiftRA#` b
903 -- | Shift the argument right (unsigned) by the specified number of bits
904 -- (which must be non-negative).
905 iShiftRL# :: Int# -> Int# -> Int#
906 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
907 | otherwise = a `uncheckedIShiftRL#` b
909 #if WORD_SIZE_IN_BITS == 32
911 "narrow32Int#" forall x#. narrow32Int# x# = x#
912 "narrow32Word#" forall x#. narrow32Word# x# = x#
917 "int2Word2Int" forall x#. int2Word# (word2Int# x#) = x#
918 "word2Int2Word" forall x#. word2Int# (int2Word# x#) = x#
923 %********************************************************
925 \subsection{Unpacking C strings}
927 %********************************************************
929 This code is needed for virtually all programs, since it's used for
930 unpacking the strings of error messages.
932 Note [Inlining for unpacking C strings]
933 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
934 We use NOINLINE on unpackCString# and unpackFoldrCString# because
935 there is little or no gain from inlining them -- and there may be a
936 lot of calls (one for each literal string).
939 unpackCString# :: Addr# -> [Char]
940 {-# NOINLINE unpackCString# #-}
941 -- See Note [Inlining for unpacking C strings]
946 | ch `eqChar#` '\0'# = []
947 | otherwise = C# ch : unpack (nh +# 1#)
949 ch = indexCharOffAddr# addr nh
951 unpackAppendCString# :: Addr# -> [Char] -> [Char]
952 unpackAppendCString# addr rest
956 | ch `eqChar#` '\0'# = rest
957 | otherwise = C# ch : unpack (nh +# 1#)
959 ch = indexCharOffAddr# addr nh
961 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
962 {-# NOINLINE unpackFoldrCString# #-}
963 -- See Note [Inlining for unpacking C strings]
964 -- Usually the unpack-list rule turns it into unpackCString#
965 -- It also has a BuiltInRule in PrelRules.lhs:
966 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n)
967 -- = unpackFoldrCString# "foobaz" c n
968 unpackFoldrCString# addr f z
972 | ch `eqChar#` '\0'# = z
973 | otherwise = C# ch `f` unpack (nh +# 1#)
975 ch = indexCharOffAddr# addr nh
977 unpackCStringUtf8# :: Addr# -> [Char]
978 unpackCStringUtf8# addr
982 | ch `eqChar#` '\0'# = []
983 | ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
984 | ch `leChar#` '\xDF'# =
985 C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
986 (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
988 | ch `leChar#` '\xEF'# =
989 C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
990 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
991 (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
994 C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
995 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
996 ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
997 (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
1000 ch = indexCharOffAddr# addr nh
1002 unpackNBytes# :: Addr# -> Int# -> [Char]
1003 unpackNBytes# _addr 0# = []
1004 unpackNBytes# addr len# = unpack [] (len# -# 1#)
1009 case indexCharOffAddr# addr i# of
1010 ch -> unpack (C# ch : acc) (i# -# 1#)
1013 "unpack" [~1] forall a . unpackCString# a = build (unpackFoldrCString# a)
1014 "unpack-list" [1] forall a . unpackFoldrCString# a (:) [] = unpackCString# a
1015 "unpack-append" forall a n . unpackFoldrCString# a (:) n = unpackAppendCString# a n
1017 -- There's a built-in rule (in PrelRules.lhs) for
1018 -- unpackFoldr "foo" c (unpackFoldr "baz" c n) = unpackFoldr "foobaz" c n
1025 -- | A special argument for the 'Control.Monad.ST.ST' type constructor,
1026 -- indexing a state embedded in the 'Prelude.IO' monad by
1027 -- 'Control.Monad.ST.stToIO'.