1 \section[GHC.Base]{Module @GHC.Base@}
3 The overall structure of the GHC Prelude is a bit tricky.
5 a) We want to avoid "orphan modules", i.e. ones with instance
6 decls that don't belong either to a tycon or a class
7 defined in the same module
9 b) We want to avoid giant modules
11 So the rough structure is as follows, in (linearised) dependency order
14 GHC.Prim Has no implementation. It defines built-in things, and
15 by importing it you bring them into scope.
16 The source file is GHC.Prim.hi-boot, which is just
17 copied to make GHC.Prim.hi
19 GHC.Base Classes: Eq, Ord, Functor, Monad
20 Types: list, (), Int, Bool, Ordering, Char, String
22 Data.Tup Types: tuples, plus instances for GHC.Base classes
24 GHC.Show Class: Show, plus instances for GHC.Base/GHC.Tup types
26 GHC.Enum Class: Enum, plus instances for GHC.Base/GHC.Tup types
28 Data.Maybe Type: Maybe, plus instances for GHC.Base classes
30 GHC.Num Class: Num, plus instances for Int
31 Type: Integer, plus instances for all classes so far (Eq, Ord, Num, Show)
33 Integer is needed here because it is mentioned in the signature
34 of 'fromInteger' in class Num
36 GHC.Real Classes: Real, Integral, Fractional, RealFrac
37 plus instances for Int, Integer
38 Types: Ratio, Rational
39 plus intances for classes so far
41 Rational is needed here because it is mentioned in the signature
42 of 'toRational' in class Real
44 Ix Classes: Ix, plus instances for Int, Bool, Char, Integer, Ordering, tuples
46 GHC.Arr Types: Array, MutableArray, MutableVar
48 Does *not* contain any ByteArray stuff (see GHC.ByteArr)
49 Arrays are used by a function in GHC.Float
51 GHC.Float Classes: Floating, RealFloat
52 Types: Float, Double, plus instances of all classes so far
54 This module contains everything to do with floating point.
55 It is a big module (900 lines)
56 With a bit of luck, many modules can be compiled without ever reading GHC.Float.hi
58 GHC.ByteArr Types: ByteArray, MutableByteArray
60 We want this one to be after GHC.Float, because it defines arrays
64 Other Prelude modules are much easier with fewer complex dependencies.
67 {-# OPTIONS -fno-implicit-prelude #-}
68 -----------------------------------------------------------------------------
71 -- Copyright : (c) The University of Glasgow, 1992-2002
72 -- License : see libraries/base/LICENSE
74 -- Maintainer : cvs-ghc@haskell.org
75 -- Stability : internal
76 -- Portability : non-portable (GHC extensions)
78 -- Basic data types and classes.
80 -----------------------------------------------------------------------------
87 module GHC.Prim, -- Re-export GHC.Prim and GHC.Err, to avoid lots
88 module GHC.Err -- of people having to import it explicitly
93 import {-# SOURCE #-} GHC.Err
97 infix 4 ==, /=, <, <=, >=, >
103 default () -- Double isn't available yet
107 %*********************************************************
109 \subsection{DEBUGGING STUFF}
110 %* (for use when compiling GHC.Base itself doesn't work)
112 %*********************************************************
116 data Bool = False | True
117 data Ordering = LT | EQ | GT
125 (&&) True True = True
131 unpackCString# :: Addr# -> [Char]
132 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
133 unpackAppendCString# :: Addr# -> [Char] -> [Char]
134 unpackCStringUtf8# :: Addr# -> [Char]
135 unpackCString# a = error "urk"
136 unpackFoldrCString# a = error "urk"
137 unpackAppendCString# a = error "urk"
138 unpackCStringUtf8# a = error "urk"
143 %*********************************************************
145 \subsection{Standard classes @Eq@, @Ord@}
147 %*********************************************************
151 -- | The 'Eq' class defines equality ('==') and inequality ('/=').
152 -- All the basic datatypes exported by the "Prelude" are instances of 'Eq',
153 -- and 'Eq' may be derived for any datatype whose constituents are also
154 -- instances of 'Eq'.
156 -- Minimal complete definition: either '==' or '/='.
159 (==), (/=) :: a -> a -> Bool
161 x /= y = not (x == y)
162 x == y = not (x /= y)
164 -- | The 'Ord' class is used for totally ordered datatypes.
166 -- Instances of 'Ord' can be derived for any user-defined
167 -- datatype whose constituent types are in 'Ord'. The declared order
168 -- of the constructors in the data declaration determines the ordering
169 -- in derived 'Ord' instances. The 'Ordering' datatype allows a single
170 -- comparison to determine the precise ordering of two objects.
172 -- Minimal complete definition: either 'compare' or '<='.
173 -- Using 'compare' can be more efficient for complex types.
175 class (Eq a) => Ord a where
176 compare :: a -> a -> Ordering
177 (<), (<=), (>), (>=) :: a -> a -> Bool
178 max, min :: a -> a -> a
182 | x <= y = LT -- NB: must be '<=' not '<' to validate the
183 -- above claim about the minimal things that
184 -- can be defined for an instance of Ord
187 x < y = case compare x y of { LT -> True; _other -> False }
188 x <= y = case compare x y of { GT -> False; _other -> True }
189 x > y = case compare x y of { GT -> True; _other -> False }
190 x >= y = case compare x y of { LT -> False; _other -> True }
192 -- These two default methods use '<=' rather than 'compare'
193 -- because the latter is often more expensive
194 max x y = if x <= y then y else x
195 min x y = if x <= y then x else y
198 %*********************************************************
200 \subsection{Monadic classes @Functor@, @Monad@ }
202 %*********************************************************
205 {- | The 'Functor' class is used for types that can be mapped over.
206 Instances of 'Functor' should satisfy the following laws:
209 > fmap (f . g) == fmap f . fmap g
211 The instances of 'Functor' for lists, 'Maybe' and 'IO' defined in the "Prelude"
215 class Functor f where
216 fmap :: (a -> b) -> f a -> f b
218 {- | The 'Monad' class defines the basic operations over a /monad/.
219 Instances of 'Monad' should satisfy the following laws:
221 > return a >>= k == k a
223 > m >>= (\x -> k x >>= h) == (m >>= k) >>= h
225 Instances of both 'Monad' and 'Functor' should additionally satisfy the law:
227 > fmap f xs == xs >>= return . f
229 The instances of 'Monad' for lists, 'Maybe' and 'IO' defined in the "Prelude"
234 (>>=) :: forall a b. m a -> (a -> m b) -> m b
235 (>>) :: forall a b. m a -> m b -> m b
236 -- Explicit for-alls so that we know what order to
237 -- give type arguments when desugaring
239 fail :: String -> m a
241 m >> k = m >>= \_ -> k
246 %*********************************************************
248 \subsection{The list type}
250 %*********************************************************
253 data [] a = [] | a : [a] -- do explicitly: deriving (Eq, Ord)
254 -- to avoid weird names like con2tag_[]#
257 instance (Eq a) => Eq [a] where
258 {-# SPECIALISE instance Eq [Char] #-}
260 (x:xs) == (y:ys) = x == y && xs == ys
263 instance (Ord a) => Ord [a] where
264 {-# SPECIALISE instance Ord [Char] #-}
266 compare [] (_:_) = LT
267 compare (_:_) [] = GT
268 compare (x:xs) (y:ys) = case compare x y of
272 instance Functor [] where
275 instance Monad [] where
276 m >>= k = foldr ((++) . k) [] m
277 m >> k = foldr ((++) . (\ _ -> k)) [] m
282 A few list functions that appear here because they are used here.
283 The rest of the prelude list functions are in GHC.List.
285 ----------------------------------------------
286 -- foldr/build/augment
287 ----------------------------------------------
290 -- | 'foldr', applied to a binary operator, a starting value (typically
291 -- the right-identity of the operator), and a list, reduces the list
292 -- using the binary operator, from right to left:
294 -- > foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
296 foldr :: (a -> b -> b) -> b -> [a] -> b
298 -- foldr f z (x:xs) = f x (foldr f z xs)
299 {-# INLINE [0] foldr #-}
300 -- Inline only in the final stage, after the foldr/cons rule has had a chance
304 go (y:ys) = y `k` go ys
306 build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
307 {-# INLINE [1] build #-}
308 -- The INLINE is important, even though build is tiny,
309 -- because it prevents [] getting inlined in the version that
310 -- appears in the interface file. If [] *is* inlined, it
311 -- won't match with [] appearing in rules in an importing module.
313 -- The "1" says to inline in phase 1
317 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
318 {-# INLINE [1] augment #-}
319 augment g xs = g (:) xs
322 "fold/build" forall k z (g::forall b. (a->b->b) -> b -> b) .
323 foldr k z (build g) = g k z
325 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) .
326 foldr k z (augment g xs) = g k (foldr k z xs)
328 "foldr/id" foldr (:) [] = \x->x
329 "foldr/app" [1] forall xs ys. foldr (:) ys xs = xs ++ ys
330 -- Only activate this from phase 1, because that's
331 -- when we disable the rule that expands (++) into foldr
333 -- The foldr/cons rule looks nice, but it can give disastrously
334 -- bloated code when commpiling
335 -- array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]
336 -- i.e. when there are very very long literal lists
337 -- So I've disabled it for now. We could have special cases
338 -- for short lists, I suppose.
339 -- "foldr/cons" forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)
341 "foldr/single" forall k z x. foldr k z [x] = k x z
342 "foldr/nil" forall k z. foldr k z [] = z
344 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)
345 (h::forall b. (a->b->b) -> b -> b) .
346 augment g (build h) = build (\c n -> g c (h c n))
347 "augment/nil" forall (g::forall b. (a->b->b) -> b -> b) .
348 augment g [] = build g
351 -- This rule is true, but not (I think) useful:
352 -- augment g (augment h t) = augment (\cn -> g c (h c n)) t
356 ----------------------------------------------
358 ----------------------------------------------
361 -- | 'map' @f xs@ is the list obtained by applying @f@ to each element
364 -- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
365 -- > map f [x1, x2, ...] == [f x1, f x2, ...]
367 map :: (a -> b) -> [a] -> [b]
369 map f (x:xs) = f x : map f xs
372 mapFB :: (elt -> lst -> lst) -> (a -> elt) -> a -> lst -> lst
373 {-# INLINE [0] mapFB #-}
374 mapFB c f x ys = c (f x) ys
376 -- The rules for map work like this.
378 -- Up to (but not including) phase 1, we use the "map" rule to
379 -- rewrite all saturated applications of map with its build/fold
380 -- form, hoping for fusion to happen.
381 -- In phase 1 and 0, we switch off that rule, inline build, and
382 -- switch on the "mapList" rule, which rewrites the foldr/mapFB
383 -- thing back into plain map.
385 -- It's important that these two rules aren't both active at once
386 -- (along with build's unfolding) else we'd get an infinite loop
387 -- in the rules. Hence the activation control below.
389 -- The "mapFB" rule optimises compositions of map.
391 -- This same pattern is followed by many other functions:
392 -- e.g. append, filter, iterate, repeat, etc.
395 "map" [~1] forall f xs. map f xs = build (\c n -> foldr (mapFB c f) n xs)
396 "mapList" [1] forall f. foldr (mapFB (:) f) [] = map f
397 "mapFB" forall c f g. mapFB (mapFB c f) g = mapFB c (f.g)
402 ----------------------------------------------
404 ----------------------------------------------
406 -- | Append two lists, i.e.,
408 -- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
409 -- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
411 -- If the first list is not finite, the result is the first list.
413 (++) :: [a] -> [a] -> [a]
415 (++) (x:xs) ys = x : xs ++ ys
418 "++" [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys
424 %*********************************************************
426 \subsection{Type @Bool@}
428 %*********************************************************
431 -- |The 'Bool' type is an enumeration. It is defined with 'False'
432 -- first so that the corresponding 'Prelude.Enum' instance will give
433 -- 'Prelude.fromEnum' 'False' the value zero, and
434 -- 'Prelude.fromEnum' 'True' the value 1.
435 data Bool = False | True deriving (Eq, Ord)
436 -- Read in GHC.Read, Show in GHC.Show
441 (&&) :: Bool -> Bool -> Bool
446 (||) :: Bool -> Bool -> Bool
455 -- |'otherwise' is defined as the value 'True'. It helps to make
456 -- guards more readable. eg.
458 -- > f x | x < 0 = ...
459 -- > | otherwise = ...
465 %*********************************************************
467 \subsection{The @()@ type}
469 %*********************************************************
471 The Unit type is here because virtually any program needs it (whereas
472 some programs may get away without consulting GHC.Tup). Furthermore,
473 the renamer currently *always* asks for () to be in scope, so that
474 ccalls can use () as their default type; so when compiling GHC.Base we
475 need (). (We could arrange suck in () only if -fglasgow-exts, but putting
476 it here seems more direct.)
479 -- | The unit datatype @()@ has one non-undefined member, the nullary
487 instance Ord () where
498 %*********************************************************
500 \subsection{Type @Ordering@}
502 %*********************************************************
505 -- | Represents an ordering relationship between two values: less
506 -- than, equal to, or greater than. An 'Ordering' is returned by
508 data Ordering = LT | EQ | GT deriving (Eq, Ord)
509 -- Read in GHC.Read, Show in GHC.Show
513 %*********************************************************
515 \subsection{Type @Char@ and @String@}
517 %*********************************************************
520 -- | A 'String' is a list of characters. String constants in Haskell are values
525 {-| The character type 'Char' is an enumeration whose values represent
526 Unicode (or equivalently ISO 10646) characters.
527 This set extends the ISO 8859-1 (Latin-1) character set
528 (the first 256 charachers), which is itself an extension of the ASCII
529 character set (the first 128 characters).
530 A character literal in Haskell has type 'Char'.
532 To convert a 'Char' to or from the corresponding 'Int' value defined
533 by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
534 'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
538 -- We don't use deriving for Eq and Ord, because for Ord the derived
539 -- instance defines only compare, which takes two primops. Then
540 -- '>' uses compare, and therefore takes two primops instead of one.
542 instance Eq Char where
543 (C# c1) == (C# c2) = c1 `eqChar#` c2
544 (C# c1) /= (C# c2) = c1 `neChar#` c2
546 instance Ord Char where
547 (C# c1) > (C# c2) = c1 `gtChar#` c2
548 (C# c1) >= (C# c2) = c1 `geChar#` c2
549 (C# c1) <= (C# c2) = c1 `leChar#` c2
550 (C# c1) < (C# c2) = c1 `ltChar#` c2
553 "x# `eqChar#` x#" forall x#. x# `eqChar#` x# = True
554 "x# `neChar#` x#" forall x#. x# `neChar#` x# = False
555 "x# `gtChar#` x#" forall x#. x# `gtChar#` x# = False
556 "x# `geChar#` x#" forall x#. x# `geChar#` x# = True
557 "x# `leChar#` x#" forall x#. x# `leChar#` x# = True
558 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
561 -- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
563 chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
564 | otherwise = error "Prelude.chr: bad argument"
566 unsafeChr :: Int -> Char
567 unsafeChr (I# i#) = C# (chr# i#)
569 -- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
571 ord (C# c#) = I# (ord# c#)
574 String equality is used when desugaring pattern-matches against strings.
577 eqString :: String -> String -> Bool
578 eqString [] [] = True
579 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
580 eqString cs1 cs2 = False
582 {-# RULES "eqString" (==) = eqString #-}
586 %*********************************************************
588 \subsection{Type @Int@}
590 %*********************************************************
594 -- ^A fixed-precision integer type with at least the range @[-2^29 .. 2^29-1]@.
595 -- The exact range for a given implementation can be determined by using
596 -- 'Prelude.minBound' and 'Prelude.maxBound' from the 'Prelude.Bounded' class.
598 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
603 {- Seems clumsy. Should perhaps put minInt and MaxInt directly into MachDeps.h -}
604 #if WORD_SIZE_IN_BITS == 31
605 minInt = I# (-0x40000000#)
606 maxInt = I# 0x3FFFFFFF#
607 #elif WORD_SIZE_IN_BITS == 32
608 minInt = I# (-0x80000000#)
609 maxInt = I# 0x7FFFFFFF#
611 minInt = I# (-0x8000000000000000#)
612 maxInt = I# 0x7FFFFFFFFFFFFFFF#
615 instance Eq Int where
619 instance Ord Int where
626 compareInt :: Int -> Int -> Ordering
627 (I# x#) `compareInt` (I# y#) = compareInt# x# y#
629 compareInt# :: Int# -> Int# -> Ordering
637 %*********************************************************
639 \subsection{The function type}
641 %*********************************************************
648 -- lazy function; this is just the same as id, but its unfolding
649 -- and strictness are over-ridden by the definition in MkId.lhs
650 -- That way, it does not get inlined, and the strictness analyser
651 -- sees it as lazy. Then the worker/wrapper phase inlines it.
656 -- Assertion function. This simply ignores its boolean argument.
657 -- The compiler may rewrite it to (assertError line)
658 -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
659 -- but from Template Haskell onwards it's simply
660 -- defined here in Base.lhs
661 assert :: Bool -> a -> a
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 -- right-associating infix application operator (useful in continuation-
680 ($) :: (a -> b) -> a -> b
683 -- until p f yields the result of applying f until p holds.
684 until :: (a -> Bool) -> (a -> a) -> a -> a
685 until p f x | p x = x
686 | otherwise = until p f (f x)
688 -- asTypeOf is a type-restricted version of const. It is usually used
689 -- as an infix operator, and its typing forces its first argument
690 -- (which is usually overloaded) to have the same type as the second.
691 asTypeOf :: a -> a -> a
695 %*********************************************************
697 \subsection{Generics}
699 %*********************************************************
704 data (:+:) a b = Inl a | Inr b
705 data (:*:) a b = a :*: b
709 %*********************************************************
711 \subsection{@getTag@}
713 %*********************************************************
715 Returns the 'tag' of a constructor application; this function is used
716 by the deriving code for Eq, Ord and Enum.
718 The primitive dataToTag# requires an evaluated constructor application
719 as its argument, so we provide getTag as a wrapper that performs the
720 evaluation before calling dataToTag#. We could have dataToTag#
721 evaluate its argument, but we prefer to do it this way because (a)
722 dataToTag# can be an inline primop if it doesn't need to do any
723 evaluation, and (b) we want to expose the evaluation to the
724 simplifier, because it might be possible to eliminate the evaluation
725 in the case when the argument is already known to be evaluated.
728 {-# INLINE getTag #-}
730 getTag x = x `seq` dataToTag# x
733 %*********************************************************
735 \subsection{Numeric primops}
737 %*********************************************************
740 divInt# :: Int# -> Int# -> Int#
742 -- Be careful NOT to overflow if we do any additional arithmetic
743 -- on the arguments... the following previous version of this
744 -- code has problems with overflow:
745 -- | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
746 -- | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
747 | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
748 | (x# <# 0#) && (y# ># 0#) = ((x# +# 1#) `quotInt#` y#) -# 1#
749 | otherwise = x# `quotInt#` y#
751 modInt# :: Int# -> Int# -> Int#
753 | (x# ># 0#) && (y# <# 0#) ||
754 (x# <# 0#) && (y# ># 0#) = if r# /=# 0# then r# +# y# else 0#
760 Definitions of the boxed PrimOps; these will be
761 used in the case of partial applications, etc.
770 {-# INLINE plusInt #-}
771 {-# INLINE minusInt #-}
772 {-# INLINE timesInt #-}
773 {-# INLINE quotInt #-}
774 {-# INLINE remInt #-}
775 {-# INLINE negateInt #-}
777 plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt, gcdInt :: Int -> Int -> Int
778 (I# x) `plusInt` (I# y) = I# (x +# y)
779 (I# x) `minusInt` (I# y) = I# (x -# y)
780 (I# x) `timesInt` (I# y) = I# (x *# y)
781 (I# x) `quotInt` (I# y) = I# (x `quotInt#` y)
782 (I# x) `remInt` (I# y) = I# (x `remInt#` y)
783 (I# x) `divInt` (I# y) = I# (x `divInt#` y)
784 (I# x) `modInt` (I# y) = I# (x `modInt#` y)
787 "x# +# 0#" forall x#. x# +# 0# = x#
788 "0# +# x#" forall x#. 0# +# x# = x#
789 "x# -# 0#" forall x#. x# -# 0# = x#
790 "x# -# x#" forall x#. x# -# x# = 0#
791 "x# *# 0#" forall x#. x# *# 0# = 0#
792 "0# *# x#" forall x#. 0# *# x# = 0#
793 "x# *# 1#" forall x#. x# *# 1# = x#
794 "1# *# x#" forall x#. 1# *# x# = x#
797 gcdInt (I# a) (I# b) = g a b
798 where g 0# 0# = error "GHC.Base.gcdInt: gcd 0 0 is undefined"
801 g _ _ = I# (gcdInt# absA absB)
803 absInt x = if x <# 0# then negateInt# x else x
808 negateInt :: Int -> Int
809 negateInt (I# x) = I# (negateInt# x)
811 gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
812 (I# x) `gtInt` (I# y) = x ># y
813 (I# x) `geInt` (I# y) = x >=# y
814 (I# x) `eqInt` (I# y) = x ==# y
815 (I# x) `neInt` (I# y) = x /=# y
816 (I# x) `ltInt` (I# y) = x <# y
817 (I# x) `leInt` (I# y) = x <=# y
820 "x# ># x#" forall x#. x# ># x# = False
821 "x# >=# x#" forall x#. x# >=# x# = True
822 "x# ==# x#" forall x#. x# ==# x# = True
823 "x# /=# x#" forall x#. x# /=# x# = False
824 "x# <# x#" forall x#. x# <# x# = False
825 "x# <=# x#" forall x#. x# <=# x# = True
829 "plusFloat x 0.0" forall x#. plusFloat# x# 0.0# = x#
830 "plusFloat 0.0 x" forall x#. plusFloat# 0.0# x# = x#
831 "minusFloat x 0.0" forall x#. minusFloat# x# 0.0# = x#
832 "minusFloat x x" forall x#. minusFloat# x# x# = 0.0#
833 "timesFloat x 0.0" forall x#. timesFloat# x# 0.0# = 0.0#
834 "timesFloat0.0 x" forall x#. timesFloat# 0.0# x# = 0.0#
835 "timesFloat x 1.0" forall x#. timesFloat# x# 1.0# = x#
836 "timesFloat 1.0 x" forall x#. timesFloat# 1.0# x# = x#
837 "divideFloat x 1.0" forall x#. divideFloat# x# 1.0# = x#
841 "plusDouble x 0.0" forall x#. (+##) x# 0.0## = x#
842 "plusDouble 0.0 x" forall x#. (+##) 0.0## x# = x#
843 "minusDouble x 0.0" forall x#. (-##) x# 0.0## = x#
844 "minusDouble x x" forall x#. (-##) x# x# = 0.0##
845 "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
846 "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
847 "timesDouble x 1.0" forall x#. (*##) x# 1.0## = x#
848 "timesDouble 1.0 x" forall x#. (*##) 1.0## x# = x#
849 "divideDouble x 1.0" forall x#. (/##) x# 1.0## = x#
852 -- Wrappers for the shift operations. The uncheckedShift# family are
853 -- undefined when the amount being shifted by is greater than the size
854 -- in bits of Int#, so these wrappers perform a check and return
855 -- either zero or -1 appropriately.
857 -- Note that these wrappers still produce undefined results when the
858 -- second argument (the shift amount) is negative.
860 shiftL#, shiftRL# :: Word# -> Int# -> Word#
862 a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
863 | otherwise = a `uncheckedShiftL#` b
865 a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
866 | otherwise = a `uncheckedShiftRL#` b
868 iShiftL#, iShiftRA#, iShiftRL# :: Int# -> Int# -> Int#
870 a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
871 | otherwise = a `uncheckedIShiftL#` b
873 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
874 | otherwise = a `uncheckedIShiftRA#` b
876 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
877 | otherwise = a `uncheckedIShiftRL#` b
879 #if WORD_SIZE_IN_BITS == 32
881 "narrow32Int#" forall x#. narrow32Int# x# = x#
882 "narrow32Word#" forall x#. narrow32Word# x# = x#
887 "int2Word2Int" forall x#. int2Word# (word2Int# x#) = x#
888 "word2Int2Word" forall x#. word2Int# (int2Word# x#) = x#
893 %********************************************************
895 \subsection{Unpacking C strings}
897 %********************************************************
899 This code is needed for virtually all programs, since it's used for
900 unpacking the strings of error messages.
903 unpackCString# :: Addr# -> [Char]
904 {-# NOINLINE [1] unpackCString# #-}
909 | ch `eqChar#` '\0'# = []
910 | otherwise = C# ch : unpack (nh +# 1#)
912 ch = indexCharOffAddr# addr nh
914 unpackAppendCString# :: Addr# -> [Char] -> [Char]
915 unpackAppendCString# addr rest
919 | ch `eqChar#` '\0'# = rest
920 | otherwise = C# ch : unpack (nh +# 1#)
922 ch = indexCharOffAddr# addr nh
924 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
925 {-# NOINLINE [0] unpackFoldrCString# #-}
926 -- Don't inline till right at the end;
927 -- usually the unpack-list rule turns it into unpackCStringList
928 unpackFoldrCString# addr f z
932 | ch `eqChar#` '\0'# = z
933 | otherwise = C# ch `f` unpack (nh +# 1#)
935 ch = indexCharOffAddr# addr nh
937 unpackCStringUtf8# :: Addr# -> [Char]
938 unpackCStringUtf8# addr
942 | ch `eqChar#` '\0'# = []
943 | ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
944 | ch `leChar#` '\xDF'# =
945 C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
946 (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
948 | ch `leChar#` '\xEF'# =
949 C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
950 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
951 (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
954 C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
955 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
956 ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
957 (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
960 ch = indexCharOffAddr# addr nh
962 unpackNBytes# :: Addr# -> Int# -> [Char]
963 unpackNBytes# _addr 0# = []
964 unpackNBytes# addr len# = unpack [] (len# -# 1#)
969 case indexCharOffAddr# addr i# of
970 ch -> unpack (C# ch : acc) (i# -# 1#)
973 "unpack" [~1] forall a . unpackCString# a = build (unpackFoldrCString# a)
974 "unpack-list" [1] forall a . unpackFoldrCString# a (:) [] = unpackCString# a
975 "unpack-append" forall a n . unpackFoldrCString# a (:) n = unpackAppendCString# a n
977 -- There's a built-in rule (in PrelRules.lhs) for
978 -- unpackFoldr "foo" c (unpackFoldr "baz" c n) = unpackFoldr "foobaz" c n
985 -- | A special argument for the 'Control.Monad.ST.ST' type constructor,
986 -- indexing a state embedded in the 'Prelude.IO' monad by
987 -- 'Control.Monad.ST.stToIO'.