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 -fno-implicit-prelude #-}
66 {-# OPTIONS_HADDOCK hide #-}
67 -----------------------------------------------------------------------------
70 -- Copyright : (c) The University of Glasgow, 1992-2002
71 -- License : see libraries/base/LICENSE
73 -- Maintainer : cvs-ghc@haskell.org
74 -- Stability : internal
75 -- Portability : non-portable (GHC extensions)
77 -- Basic data types and classes.
79 -----------------------------------------------------------------------------
89 module GHC.Prim, -- Re-export GHC.Prim and GHC.Err, to avoid lots
90 module GHC.Err -- of people having to import it explicitly
97 import {-# SOURCE #-} GHC.Err
101 infix 4 ==, /=, <, <=, >=, >
107 default () -- Double isn't available yet
111 %*********************************************************
113 \subsection{DEBUGGING STUFF}
114 %* (for use when compiling GHC.Base itself doesn't work)
116 %*********************************************************
120 data Bool = False | True
121 data Ordering = LT | EQ | GT
129 (&&) True True = True
135 unpackCString# :: Addr# -> [Char]
136 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
137 unpackAppendCString# :: Addr# -> [Char] -> [Char]
138 unpackCStringUtf8# :: Addr# -> [Char]
139 unpackCString# a = error "urk"
140 unpackFoldrCString# a = error "urk"
141 unpackAppendCString# a = error "urk"
142 unpackCStringUtf8# a = error "urk"
147 %*********************************************************
149 \subsection{Standard classes @Eq@, @Ord@}
151 %*********************************************************
155 -- | The 'Eq' class defines equality ('==') and inequality ('/=').
156 -- All the basic datatypes exported by the "Prelude" are instances of 'Eq',
157 -- and 'Eq' may be derived for any datatype whose constituents are also
158 -- instances of 'Eq'.
160 -- Minimal complete definition: either '==' or '/='.
163 (==), (/=) :: a -> a -> Bool
165 x /= y = not (x == y)
166 x == y = not (x /= y)
168 -- | The 'Ord' class is used for totally ordered datatypes.
170 -- Instances of 'Ord' can be derived for any user-defined
171 -- datatype whose constituent types are in 'Ord'. The declared order
172 -- of the constructors in the data declaration determines the ordering
173 -- in derived 'Ord' instances. The 'Ordering' datatype allows a single
174 -- comparison to determine the precise ordering of two objects.
176 -- Minimal complete definition: either 'compare' or '<='.
177 -- Using 'compare' can be more efficient for complex types.
179 class (Eq a) => Ord a where
180 compare :: a -> a -> Ordering
181 (<), (<=), (>), (>=) :: a -> a -> Bool
182 max, min :: a -> a -> a
186 | x <= y = LT -- NB: must be '<=' not '<' to validate the
187 -- above claim about the minimal things that
188 -- can be defined for an instance of Ord
191 x < y = case compare x y of { LT -> True; _other -> False }
192 x <= y = case compare x y of { GT -> False; _other -> True }
193 x > y = case compare x y of { GT -> True; _other -> False }
194 x >= y = case compare x y of { LT -> False; _other -> True }
196 -- These two default methods use '<=' rather than 'compare'
197 -- because the latter is often more expensive
198 max x y = if x <= y then y else x
199 min x y = if x <= y then x else y
202 %*********************************************************
204 \subsection{Monadic classes @Functor@, @Monad@ }
206 %*********************************************************
209 {- | The 'Functor' class is used for types that can be mapped over.
210 Instances of 'Functor' should satisfy the following laws:
213 > fmap (f . g) == fmap f . fmap g
215 The instances of 'Functor' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
216 defined in the "Prelude" satisfy these laws.
219 class Functor f where
220 fmap :: (a -> b) -> f a -> f b
222 {- | The 'Monad' class defines the basic operations over a /monad/,
223 a concept from a branch of mathematics known as /category theory/.
224 From the perspective of a Haskell programmer, however, it is best to
225 think of a monad as an /abstract datatype/ of actions.
226 Haskell's @do@ expressions provide a convenient syntax for writing
229 Minimal complete definition: '>>=' and 'return'.
231 Instances of 'Monad' should satisfy the following laws:
233 > return a >>= k == k a
235 > m >>= (\x -> k x >>= h) == (m >>= k) >>= h
237 Instances of both 'Monad' and 'Functor' should additionally satisfy the law:
239 > fmap f xs == xs >>= return . f
241 The instances of 'Monad' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
242 defined in the "Prelude" satisfy these laws.
246 -- | Sequentially compose two actions, passing any value produced
247 -- by the first as an argument to the second.
248 (>>=) :: forall a b. m a -> (a -> m b) -> m b
249 -- | Sequentially compose two actions, discarding any value produced
250 -- by the first, like sequencing operators (such as the semicolon)
251 -- in imperative languages.
252 (>>) :: forall a b. m a -> m b -> m b
253 -- Explicit for-alls so that we know what order to
254 -- give type arguments when desugaring
256 -- | Inject a value into the monadic type.
258 -- | Fail with a message. This operation is not part of the
259 -- mathematical definition of a monad, but is invoked on pattern-match
260 -- failure in a @do@ expression.
261 fail :: String -> m a
263 m >> k = m >>= \_ -> k
268 %*********************************************************
270 \subsection{The list type}
272 %*********************************************************
275 data [] a = [] | a : [a] -- do explicitly: deriving (Eq, Ord)
276 -- to avoid weird names like con2tag_[]#
279 instance (Eq a) => Eq [a] where
280 {-# SPECIALISE instance Eq [Char] #-}
282 (x:xs) == (y:ys) = x == y && xs == ys
285 instance (Ord a) => Ord [a] where
286 {-# SPECIALISE instance Ord [Char] #-}
288 compare [] (_:_) = LT
289 compare (_:_) [] = GT
290 compare (x:xs) (y:ys) = case compare x y of
294 instance Functor [] where
297 instance Monad [] where
298 m >>= k = foldr ((++) . k) [] m
299 m >> k = foldr ((++) . (\ _ -> k)) [] m
304 A few list functions that appear here because they are used here.
305 The rest of the prelude list functions are in GHC.List.
307 ----------------------------------------------
308 -- foldr/build/augment
309 ----------------------------------------------
312 -- | 'foldr', applied to a binary operator, a starting value (typically
313 -- the right-identity of the operator), and a list, reduces the list
314 -- using the binary operator, from right to left:
316 -- > foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
318 foldr :: (a -> b -> b) -> b -> [a] -> b
320 -- foldr f z (x:xs) = f x (foldr f z xs)
321 {-# INLINE [0] foldr #-}
322 -- Inline only in the final stage, after the foldr/cons rule has had a chance
326 go (y:ys) = y `k` go ys
328 -- | A list producer that can be fused with 'foldr'.
329 -- This function is merely
331 -- > build g = g (:) []
333 -- but GHC's simplifier will transform an expression of the form
334 -- @'foldr' k z ('build' g)@, which may arise after inlining, to @g k z@,
335 -- which avoids producing an intermediate list.
337 build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
338 {-# INLINE [1] build #-}
339 -- The INLINE is important, even though build is tiny,
340 -- because it prevents [] getting inlined in the version that
341 -- appears in the interface file. If [] *is* inlined, it
342 -- won't match with [] appearing in rules in an importing module.
344 -- The "1" says to inline in phase 1
348 -- | A list producer that can be fused with 'foldr'.
349 -- This function is merely
351 -- > augment g xs = g (:) xs
353 -- but GHC's simplifier will transform an expression of the form
354 -- @'foldr' k z ('augment' g xs)@, which may arise after inlining, to
355 -- @g k ('foldr' k z xs)@, which avoids producing an intermediate list.
357 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
358 {-# INLINE [1] augment #-}
359 augment g xs = g (:) xs
362 "fold/build" forall k z (g::forall b. (a->b->b) -> b -> b) .
363 foldr k z (build g) = g k z
365 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) .
366 foldr k z (augment g xs) = g k (foldr k z xs)
368 "foldr/id" foldr (:) [] = \x -> x
369 "foldr/app" [1] forall ys. foldr (:) ys = \xs -> xs ++ ys
370 -- Only activate this from phase 1, because that's
371 -- when we disable the rule that expands (++) into foldr
373 -- The foldr/cons rule looks nice, but it can give disastrously
374 -- bloated code when commpiling
375 -- array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]
376 -- i.e. when there are very very long literal lists
377 -- So I've disabled it for now. We could have special cases
378 -- for short lists, I suppose.
379 -- "foldr/cons" forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)
381 "foldr/single" forall k z x. foldr k z [x] = k x z
382 "foldr/nil" forall k z. foldr k z [] = z
384 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)
385 (h::forall b. (a->b->b) -> b -> b) .
386 augment g (build h) = build (\c n -> g c (h c n))
387 "augment/nil" forall (g::forall b. (a->b->b) -> b -> b) .
388 augment g [] = build g
391 -- This rule is true, but not (I think) useful:
392 -- augment g (augment h t) = augment (\cn -> g c (h c n)) t
396 ----------------------------------------------
398 ----------------------------------------------
401 -- | 'map' @f xs@ is the list obtained by applying @f@ to each element
404 -- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
405 -- > map f [x1, x2, ...] == [f x1, f x2, ...]
407 map :: (a -> b) -> [a] -> [b]
409 map f (x:xs) = f x : map f xs
412 mapFB :: (elt -> lst -> lst) -> (a -> elt) -> a -> lst -> lst
413 {-# INLINE [0] mapFB #-}
414 mapFB c f x ys = c (f x) ys
416 -- The rules for map work like this.
418 -- Up to (but not including) phase 1, we use the "map" rule to
419 -- rewrite all saturated applications of map with its build/fold
420 -- form, hoping for fusion to happen.
421 -- In phase 1 and 0, we switch off that rule, inline build, and
422 -- switch on the "mapList" rule, which rewrites the foldr/mapFB
423 -- thing back into plain map.
425 -- It's important that these two rules aren't both active at once
426 -- (along with build's unfolding) else we'd get an infinite loop
427 -- in the rules. Hence the activation control below.
429 -- The "mapFB" rule optimises compositions of map.
431 -- This same pattern is followed by many other functions:
432 -- e.g. append, filter, iterate, repeat, etc.
435 "map" [~1] forall f xs. map f xs = build (\c n -> foldr (mapFB c f) n xs)
436 "mapList" [1] forall f. foldr (mapFB (:) f) [] = map f
437 "mapFB" forall c f g. mapFB (mapFB c f) g = mapFB c (f.g)
442 ----------------------------------------------
444 ----------------------------------------------
446 -- | Append two lists, i.e.,
448 -- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
449 -- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
451 -- If the first list is not finite, the result is the first list.
453 (++) :: [a] -> [a] -> [a]
455 (++) (x:xs) ys = x : xs ++ ys
458 "++" [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys
464 %*********************************************************
466 \subsection{Type @Bool@}
468 %*********************************************************
471 -- |The 'Bool' type is an enumeration. It is defined with 'False'
472 -- first so that the corresponding 'Prelude.Enum' instance will give
473 -- 'Prelude.fromEnum' 'False' the value zero, and
474 -- 'Prelude.fromEnum' 'True' the value 1.
475 -- The actual definition is in the ghc-prim package.
477 -- XXX These don't work:
478 -- deriving instance Eq Bool
479 -- deriving instance Ord Bool
480 -- <wired into compiler>:
481 -- Illegal binding of built-in syntax: con2tag_Bool#
483 instance Eq Bool where
485 False == False = True
488 instance Ord Bool where
489 compare False True = LT
490 compare True False = GT
493 -- Read is in GHC.Read, Show in GHC.Show
498 (&&) :: Bool -> Bool -> Bool
503 (||) :: Bool -> Bool -> Bool
512 -- |'otherwise' is defined as the value 'True'. It helps to make
513 -- guards more readable. eg.
515 -- > f x | x < 0 = ...
516 -- > | otherwise = ...
521 %*********************************************************
523 \subsection{The @()@ type}
525 %*********************************************************
527 The Unit type is here because virtually any program needs it (whereas
528 some programs may get away without consulting GHC.Tup). Furthermore,
529 the renamer currently *always* asks for () to be in scope, so that
530 ccalls can use () as their default type; so when compiling GHC.Base we
531 need (). (We could arrange suck in () only if -fglasgow-exts, but putting
532 it here seems more direct.)
535 -- | The unit datatype @()@ has one non-undefined member, the nullary
543 instance Ord () where
554 %*********************************************************
556 \subsection{Type @Ordering@}
558 %*********************************************************
561 -- | Represents an ordering relationship between two values: less
562 -- than, equal to, or greater than. An 'Ordering' is returned by
564 data Ordering = LT | EQ | GT deriving (Eq, Ord)
565 -- Read in GHC.Read, Show in GHC.Show
569 %*********************************************************
571 \subsection{Type @Char@ and @String@}
573 %*********************************************************
576 -- | A 'String' is a list of characters. String constants in Haskell are values
581 {-| The character type 'Char' is an enumeration whose values represent
582 Unicode (or equivalently ISO\/IEC 10646) characters
583 (see <http://www.unicode.org/> for details).
584 This set extends the ISO 8859-1 (Latin-1) character set
585 (the first 256 charachers), which is itself an extension of the ASCII
586 character set (the first 128 characters).
587 A character literal in Haskell has type 'Char'.
589 To convert a 'Char' to or from the corresponding 'Int' value defined
590 by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
591 'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
595 -- We don't use deriving for Eq and Ord, because for Ord the derived
596 -- instance defines only compare, which takes two primops. Then
597 -- '>' uses compare, and therefore takes two primops instead of one.
599 instance Eq Char where
600 (C# c1) == (C# c2) = c1 `eqChar#` c2
601 (C# c1) /= (C# c2) = c1 `neChar#` c2
603 instance Ord Char where
604 (C# c1) > (C# c2) = c1 `gtChar#` c2
605 (C# c1) >= (C# c2) = c1 `geChar#` c2
606 (C# c1) <= (C# c2) = c1 `leChar#` c2
607 (C# c1) < (C# c2) = c1 `ltChar#` c2
610 "x# `eqChar#` x#" forall x#. x# `eqChar#` x# = True
611 "x# `neChar#` x#" forall x#. x# `neChar#` x# = False
612 "x# `gtChar#` x#" forall x#. x# `gtChar#` x# = False
613 "x# `geChar#` x#" forall x#. x# `geChar#` x# = True
614 "x# `leChar#` x#" forall x#. x# `leChar#` x# = True
615 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
618 -- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
620 chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
621 | otherwise = error "Prelude.chr: bad argument"
623 unsafeChr :: Int -> Char
624 unsafeChr (I# i#) = C# (chr# i#)
626 -- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
628 ord (C# c#) = I# (ord# c#)
631 String equality is used when desugaring pattern-matches against strings.
634 eqString :: String -> String -> Bool
635 eqString [] [] = True
636 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
637 eqString cs1 cs2 = False
639 {-# RULES "eqString" (==) = eqString #-}
640 -- eqString also has a BuiltInRule in PrelRules.lhs:
641 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
645 %*********************************************************
647 \subsection{Type @Int@}
649 %*********************************************************
653 -- ^A fixed-precision integer type with at least the range @[-2^29 .. 2^29-1]@.
654 -- The exact range for a given implementation can be determined by using
655 -- 'Prelude.minBound' and 'Prelude.maxBound' from the 'Prelude.Bounded' class.
657 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
662 {- Seems clumsy. Should perhaps put minInt and MaxInt directly into MachDeps.h -}
663 #if WORD_SIZE_IN_BITS == 31
664 minInt = I# (-0x40000000#)
665 maxInt = I# 0x3FFFFFFF#
666 #elif WORD_SIZE_IN_BITS == 32
667 minInt = I# (-0x80000000#)
668 maxInt = I# 0x7FFFFFFF#
670 minInt = I# (-0x8000000000000000#)
671 maxInt = I# 0x7FFFFFFFFFFFFFFF#
674 instance Eq Int where
678 instance Ord Int where
685 compareInt :: Int -> Int -> Ordering
686 (I# x#) `compareInt` (I# y#) = compareInt# x# y#
688 compareInt# :: Int# -> Int# -> Ordering
696 %*********************************************************
698 \subsection{The function type}
700 %*********************************************************
703 -- | Identity function.
707 -- | The call '(lazy e)' means the same as 'e', but 'lazy' has a
708 -- magical strictness property: it is lazy in its first argument,
709 -- even though its semantics is strict.
712 -- Implementation note: its strictness and unfolding are over-ridden
713 -- by the definition in MkId.lhs; in both cases to nothing at all.
714 -- That way, 'lazy' does not get inlined, and the strictness analyser
715 -- sees it as lazy. Then the worker/wrapper phase inlines it.
719 -- | The call '(inline f)' reduces to 'f', but 'inline' has a BuiltInRule
720 -- that tries to inline 'f' (if it has an unfolding) unconditionally
721 -- The 'NOINLINE' pragma arranges that inline only gets inlined (and
722 -- hence eliminated) late in compilation, after the rule has had
723 -- a god chance to fire.
725 {-# NOINLINE[0] inline #-}
728 -- Assertion function. This simply ignores its boolean argument.
729 -- The compiler may rewrite it to @('assertError' line)@.
731 -- | If the first argument evaluates to 'True', then the result is the
732 -- second argument. Otherwise an 'AssertionFailed' exception is raised,
733 -- containing a 'String' with the source file and line number of the
736 -- Assertions can normally be turned on or off with a compiler flag
737 -- (for GHC, assertions are normally on unless optimisation is turned on
738 -- with @-O@ or the @-fignore-asserts@
739 -- option is given). When assertions are turned off, the first
740 -- argument to 'assert' is ignored, and the second argument is
741 -- returned as the result.
743 -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
744 -- but from Template Haskell onwards it's simply
745 -- defined here in Base.lhs
746 assert :: Bool -> a -> a
752 breakpointCond :: Bool -> a -> a
753 breakpointCond _ r = r
755 data Opaque = forall a. O a
757 -- | Constant function.
761 -- | Function composition.
763 (.) :: (b -> c) -> (a -> b) -> a -> c
766 -- | @'flip' f@ takes its (first) two arguments in the reverse order of @f@.
767 flip :: (a -> b -> c) -> b -> a -> c
770 -- | Application operator. This operator is redundant, since ordinary
771 -- application @(f x)@ means the same as @(f '$' x)@. However, '$' has
772 -- low, right-associative binding precedence, so it sometimes allows
773 -- parentheses to be omitted; for example:
775 -- > f $ g $ h x = f (g (h x))
777 -- It is also useful in higher-order situations, such as @'map' ('$' 0) xs@,
778 -- or @'Data.List.zipWith' ('$') fs xs@.
780 ($) :: (a -> b) -> a -> b
783 -- | @'until' p f@ yields the result of applying @f@ until @p@ holds.
784 until :: (a -> Bool) -> (a -> a) -> a -> a
785 until p f x | p x = x
786 | otherwise = until p f (f x)
788 -- | 'asTypeOf' is a type-restricted version of 'const'. It is usually
789 -- used as an infix operator, and its typing forces its first argument
790 -- (which is usually overloaded) to have the same type as the second.
791 asTypeOf :: a -> a -> a
795 %*********************************************************
797 \subsection{@getTag@}
799 %*********************************************************
801 Returns the 'tag' of a constructor application; this function is used
802 by the deriving code for Eq, Ord and Enum.
804 The primitive dataToTag# requires an evaluated constructor application
805 as its argument, so we provide getTag as a wrapper that performs the
806 evaluation before calling dataToTag#. We could have dataToTag#
807 evaluate its argument, but we prefer to do it this way because (a)
808 dataToTag# can be an inline primop if it doesn't need to do any
809 evaluation, and (b) we want to expose the evaluation to the
810 simplifier, because it might be possible to eliminate the evaluation
811 in the case when the argument is already known to be evaluated.
814 {-# INLINE getTag #-}
816 getTag x = x `seq` dataToTag# x
819 %*********************************************************
821 \subsection{Numeric primops}
823 %*********************************************************
826 divInt# :: Int# -> Int# -> Int#
828 -- Be careful NOT to overflow if we do any additional arithmetic
829 -- on the arguments... the following previous version of this
830 -- code has problems with overflow:
831 -- | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
832 -- | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
833 | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
834 | (x# <# 0#) && (y# ># 0#) = ((x# +# 1#) `quotInt#` y#) -# 1#
835 | otherwise = x# `quotInt#` y#
837 modInt# :: Int# -> Int# -> Int#
839 | (x# ># 0#) && (y# <# 0#) ||
840 (x# <# 0#) && (y# ># 0#) = if r# /=# 0# then r# +# y# else 0#
846 Definitions of the boxed PrimOps; these will be
847 used in the case of partial applications, etc.
856 {-# INLINE plusInt #-}
857 {-# INLINE minusInt #-}
858 {-# INLINE timesInt #-}
859 {-# INLINE quotInt #-}
860 {-# INLINE remInt #-}
861 {-# INLINE negateInt #-}
863 plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt, gcdInt :: Int -> Int -> Int
864 (I# x) `plusInt` (I# y) = I# (x +# y)
865 (I# x) `minusInt` (I# y) = I# (x -# y)
866 (I# x) `timesInt` (I# y) = I# (x *# y)
867 (I# x) `quotInt` (I# y) = I# (x `quotInt#` y)
868 (I# x) `remInt` (I# y) = I# (x `remInt#` y)
869 (I# x) `divInt` (I# y) = I# (x `divInt#` y)
870 (I# x) `modInt` (I# y) = I# (x `modInt#` y)
873 "x# +# 0#" forall x#. x# +# 0# = x#
874 "0# +# x#" forall x#. 0# +# x# = x#
875 "x# -# 0#" forall x#. x# -# 0# = x#
876 "x# -# x#" forall x#. x# -# x# = 0#
877 "x# *# 0#" forall x#. x# *# 0# = 0#
878 "0# *# x#" forall x#. 0# *# x# = 0#
879 "x# *# 1#" forall x#. x# *# 1# = x#
880 "1# *# x#" forall x#. 1# *# x# = x#
883 gcdInt (I# a) (I# b) = g a b
884 where g 0# 0# = error "GHC.Base.gcdInt: gcd 0 0 is undefined"
887 g _ _ = I# (gcdInt# absA absB)
889 absInt x = if x <# 0# then negateInt# x else x
894 negateInt :: Int -> Int
895 negateInt (I# x) = I# (negateInt# x)
897 gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
898 (I# x) `gtInt` (I# y) = x ># y
899 (I# x) `geInt` (I# y) = x >=# y
900 (I# x) `eqInt` (I# y) = x ==# y
901 (I# x) `neInt` (I# y) = x /=# y
902 (I# x) `ltInt` (I# y) = x <# y
903 (I# x) `leInt` (I# y) = x <=# y
906 "x# ># x#" forall x#. x# ># x# = False
907 "x# >=# x#" forall x#. x# >=# x# = True
908 "x# ==# x#" forall x#. x# ==# x# = True
909 "x# /=# x#" forall x#. x# /=# x# = False
910 "x# <# x#" forall x#. x# <# x# = False
911 "x# <=# x#" forall x#. x# <=# x# = True
915 "plusFloat x 0.0" forall x#. plusFloat# x# 0.0# = x#
916 "plusFloat 0.0 x" forall x#. plusFloat# 0.0# x# = x#
917 "minusFloat x 0.0" forall x#. minusFloat# x# 0.0# = x#
918 "minusFloat x x" forall x#. minusFloat# x# x# = 0.0#
919 "timesFloat x 0.0" forall x#. timesFloat# x# 0.0# = 0.0#
920 "timesFloat0.0 x" forall x#. timesFloat# 0.0# x# = 0.0#
921 "timesFloat x 1.0" forall x#. timesFloat# x# 1.0# = x#
922 "timesFloat 1.0 x" forall x#. timesFloat# 1.0# x# = x#
923 "divideFloat x 1.0" forall x#. divideFloat# x# 1.0# = x#
927 "plusDouble x 0.0" forall x#. (+##) x# 0.0## = x#
928 "plusDouble 0.0 x" forall x#. (+##) 0.0## x# = x#
929 "minusDouble x 0.0" forall x#. (-##) x# 0.0## = x#
930 "timesDouble x 1.0" forall x#. (*##) x# 1.0## = x#
931 "timesDouble 1.0 x" forall x#. (*##) 1.0## x# = x#
932 "divideDouble x 1.0" forall x#. (/##) x# 1.0## = x#
936 We'd like to have more rules, but for example:
938 This gives wrong answer (0) for NaN - NaN (should be NaN):
939 "minusDouble x x" forall x#. (-##) x# x# = 0.0##
941 This gives wrong answer (0) for 0 * NaN (should be NaN):
942 "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
944 This gives wrong answer (0) for NaN * 0 (should be NaN):
945 "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
947 These are tested by num014.
950 -- Wrappers for the shift operations. The uncheckedShift# family are
951 -- undefined when the amount being shifted by is greater than the size
952 -- in bits of Int#, so these wrappers perform a check and return
953 -- either zero or -1 appropriately.
955 -- Note that these wrappers still produce undefined results when the
956 -- second argument (the shift amount) is negative.
958 -- | Shift the argument left by the specified number of bits
959 -- (which must be non-negative).
960 shiftL# :: Word# -> Int# -> Word#
961 a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
962 | otherwise = a `uncheckedShiftL#` b
964 -- | Shift the argument right by the specified number of bits
965 -- (which must be non-negative).
966 shiftRL# :: Word# -> Int# -> Word#
967 a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
968 | otherwise = a `uncheckedShiftRL#` b
970 -- | Shift the argument left by the specified number of bits
971 -- (which must be non-negative).
972 iShiftL# :: Int# -> Int# -> Int#
973 a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
974 | otherwise = a `uncheckedIShiftL#` b
976 -- | Shift the argument right (signed) by the specified number of bits
977 -- (which must be non-negative).
978 iShiftRA# :: Int# -> Int# -> Int#
979 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
980 | otherwise = a `uncheckedIShiftRA#` b
982 -- | Shift the argument right (unsigned) by the specified number of bits
983 -- (which must be non-negative).
984 iShiftRL# :: Int# -> Int# -> Int#
985 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
986 | otherwise = a `uncheckedIShiftRL#` b
988 #if WORD_SIZE_IN_BITS == 32
990 "narrow32Int#" forall x#. narrow32Int# x# = x#
991 "narrow32Word#" forall x#. narrow32Word# x# = x#
996 "int2Word2Int" forall x#. int2Word# (word2Int# x#) = x#
997 "word2Int2Word" forall x#. word2Int# (int2Word# x#) = x#
1002 %********************************************************
1004 \subsection{Unpacking C strings}
1006 %********************************************************
1008 This code is needed for virtually all programs, since it's used for
1009 unpacking the strings of error messages.
1012 unpackCString# :: Addr# -> [Char]
1013 {-# NOINLINE [1] unpackCString# #-}
1018 | ch `eqChar#` '\0'# = []
1019 | otherwise = C# ch : unpack (nh +# 1#)
1021 ch = indexCharOffAddr# addr nh
1023 unpackAppendCString# :: Addr# -> [Char] -> [Char]
1024 unpackAppendCString# addr rest
1028 | ch `eqChar#` '\0'# = rest
1029 | otherwise = C# ch : unpack (nh +# 1#)
1031 ch = indexCharOffAddr# addr nh
1033 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
1034 {-# NOINLINE [0] unpackFoldrCString# #-}
1035 -- Don't inline till right at the end;
1036 -- usually the unpack-list rule turns it into unpackCStringList
1037 -- It also has a BuiltInRule in PrelRules.lhs:
1038 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n)
1039 -- = unpackFoldrCString# "foobaz" c n
1040 unpackFoldrCString# addr f z
1044 | ch `eqChar#` '\0'# = z
1045 | otherwise = C# ch `f` unpack (nh +# 1#)
1047 ch = indexCharOffAddr# addr nh
1049 unpackCStringUtf8# :: Addr# -> [Char]
1050 unpackCStringUtf8# addr
1054 | ch `eqChar#` '\0'# = []
1055 | ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
1056 | ch `leChar#` '\xDF'# =
1057 C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
1058 (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
1060 | ch `leChar#` '\xEF'# =
1061 C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
1062 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
1063 (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
1066 C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
1067 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
1068 ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
1069 (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
1072 ch = indexCharOffAddr# addr nh
1074 unpackNBytes# :: Addr# -> Int# -> [Char]
1075 unpackNBytes# _addr 0# = []
1076 unpackNBytes# addr len# = unpack [] (len# -# 1#)
1081 case indexCharOffAddr# addr i# of
1082 ch -> unpack (C# ch : acc) (i# -# 1#)
1085 "unpack" [~1] forall a . unpackCString# a = build (unpackFoldrCString# a)
1086 "unpack-list" [1] forall a . unpackFoldrCString# a (:) [] = unpackCString# a
1087 "unpack-append" forall a n . unpackFoldrCString# a (:) n = unpackAppendCString# a n
1089 -- There's a built-in rule (in PrelRules.lhs) for
1090 -- unpackFoldr "foo" c (unpackFoldr "baz" c n) = unpackFoldr "foobaz" c n
1097 -- | A special argument for the 'Control.Monad.ST.ST' type constructor,
1098 -- indexing a state embedded in the 'Prelude.IO' monad by
1099 -- 'Control.Monad.ST.stToIO'.