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_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 -----------------------------------------------------------------------------
90 module GHC.Prim, -- Re-export GHC.Prim and GHC.Err, to avoid lots
91 module GHC.Err -- of people having to import it explicitly
99 import {-# SOURCE #-} GHC.Err
103 infix 4 ==, /=, <, <=, >=, >
109 default () -- Double isn't available yet
113 %*********************************************************
115 \subsection{DEBUGGING STUFF}
116 %* (for use when compiling GHC.Base itself doesn't work)
118 %*********************************************************
122 data Bool = False | True
123 data Ordering = LT | EQ | GT
131 (&&) True True = True
137 unpackCString# :: Addr# -> [Char]
138 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
139 unpackAppendCString# :: Addr# -> [Char] -> [Char]
140 unpackCStringUtf8# :: Addr# -> [Char]
141 unpackCString# a = error "urk"
142 unpackFoldrCString# a = error "urk"
143 unpackAppendCString# a = error "urk"
144 unpackCStringUtf8# a = error "urk"
149 %*********************************************************
151 \subsection{Standard classes @Eq@, @Ord@}
153 %*********************************************************
157 -- | The 'Eq' class defines equality ('==') and inequality ('/=').
158 -- All the basic datatypes exported by the "Prelude" are instances of 'Eq',
159 -- and 'Eq' may be derived for any datatype whose constituents are also
160 -- instances of 'Eq'.
162 -- Minimal complete definition: either '==' or '/='.
165 (==), (/=) :: a -> a -> Bool
167 x /= y = not (x == y)
168 x == y = not (x /= y)
170 -- | The 'Ord' class is used for totally ordered datatypes.
172 -- Instances of 'Ord' can be derived for any user-defined
173 -- datatype whose constituent types are in 'Ord'. The declared order
174 -- of the constructors in the data declaration determines the ordering
175 -- in derived 'Ord' instances. The 'Ordering' datatype allows a single
176 -- comparison to determine the precise ordering of two objects.
178 -- Minimal complete definition: either 'compare' or '<='.
179 -- Using 'compare' can be more efficient for complex types.
181 class (Eq a) => Ord a where
182 compare :: a -> a -> Ordering
183 (<), (<=), (>), (>=) :: a -> a -> Bool
184 max, min :: a -> a -> a
188 | x <= y = LT -- NB: must be '<=' not '<' to validate the
189 -- above claim about the minimal things that
190 -- can be defined for an instance of Ord
193 x < y = case compare x y of { LT -> True; _other -> False }
194 x <= y = case compare x y of { GT -> False; _other -> True }
195 x > y = case compare x y of { GT -> True; _other -> False }
196 x >= y = case compare x y of { LT -> False; _other -> True }
198 -- These two default methods use '<=' rather than 'compare'
199 -- because the latter is often more expensive
200 max x y = if x <= y then y else x
201 min x y = if x <= y then x else y
204 %*********************************************************
206 \subsection{Monadic classes @Functor@, @Monad@ }
208 %*********************************************************
211 {- | The 'Functor' class is used for types that can be mapped over.
212 Instances of 'Functor' should satisfy the following laws:
215 > fmap (f . g) == fmap f . fmap g
217 The instances of 'Functor' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
218 defined in the "Prelude" satisfy these laws.
221 class Functor f where
222 fmap :: (a -> b) -> f a -> f b
224 {- | The 'Monad' class defines the basic operations over a /monad/,
225 a concept from a branch of mathematics known as /category theory/.
226 From the perspective of a Haskell programmer, however, it is best to
227 think of a monad as an /abstract datatype/ of actions.
228 Haskell's @do@ expressions provide a convenient syntax for writing
231 Minimal complete definition: '>>=' and 'return'.
233 Instances of 'Monad' should satisfy the following laws:
235 > return a >>= k == k a
237 > m >>= (\x -> k x >>= h) == (m >>= k) >>= h
239 Instances of both 'Monad' and 'Functor' should additionally satisfy the law:
241 > fmap f xs == xs >>= return . f
243 The instances of 'Monad' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
244 defined in the "Prelude" satisfy these laws.
248 -- | Sequentially compose two actions, passing any value produced
249 -- by the first as an argument to the second.
250 (>>=) :: forall a b. m a -> (a -> m b) -> m b
251 -- | Sequentially compose two actions, discarding any value produced
252 -- by the first, like sequencing operators (such as the semicolon)
253 -- in imperative languages.
254 (>>) :: forall a b. m a -> m b -> m b
255 -- Explicit for-alls so that we know what order to
256 -- give type arguments when desugaring
258 -- | Inject a value into the monadic type.
260 -- | Fail with a message. This operation is not part of the
261 -- mathematical definition of a monad, but is invoked on pattern-match
262 -- failure in a @do@ expression.
263 fail :: String -> m a
265 m >> k = m >>= \_ -> k
270 %*********************************************************
272 \subsection{The list type}
274 %*********************************************************
277 data [] a = [] | a : [a] -- do explicitly: deriving (Eq, Ord)
278 -- to avoid weird names like con2tag_[]#
281 instance (Eq a) => Eq [a] where
282 {-# SPECIALISE instance Eq [Char] #-}
284 (x:xs) == (y:ys) = x == y && xs == ys
287 instance (Ord a) => Ord [a] where
288 {-# SPECIALISE instance Ord [Char] #-}
290 compare [] (_:_) = LT
291 compare (_:_) [] = GT
292 compare (x:xs) (y:ys) = case compare x y of
296 instance Functor [] where
299 instance Monad [] where
300 m >>= k = foldr ((++) . k) [] m
301 m >> k = foldr ((++) . (\ _ -> k)) [] m
306 A few list functions that appear here because they are used here.
307 The rest of the prelude list functions are in GHC.List.
309 ----------------------------------------------
310 -- foldr/build/augment
311 ----------------------------------------------
314 -- | 'foldr', applied to a binary operator, a starting value (typically
315 -- the right-identity of the operator), and a list, reduces the list
316 -- using the binary operator, from right to left:
318 -- > foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
320 foldr :: (a -> b -> b) -> b -> [a] -> b
322 -- foldr f z (x:xs) = f x (foldr f z xs)
323 {-# INLINE [0] foldr #-}
324 -- Inline only in the final stage, after the foldr/cons rule has had a chance
328 go (y:ys) = y `k` go ys
330 -- | A list producer that can be fused with 'foldr'.
331 -- This function is merely
333 -- > build g = g (:) []
335 -- but GHC's simplifier will transform an expression of the form
336 -- @'foldr' k z ('build' g)@, which may arise after inlining, to @g k z@,
337 -- which avoids producing an intermediate list.
339 build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
340 {-# INLINE [1] build #-}
341 -- The INLINE is important, even though build is tiny,
342 -- because it prevents [] getting inlined in the version that
343 -- appears in the interface file. If [] *is* inlined, it
344 -- won't match with [] appearing in rules in an importing module.
346 -- The "1" says to inline in phase 1
350 -- | A list producer that can be fused with 'foldr'.
351 -- This function is merely
353 -- > augment g xs = g (:) xs
355 -- but GHC's simplifier will transform an expression of the form
356 -- @'foldr' k z ('augment' g xs)@, which may arise after inlining, to
357 -- @g k ('foldr' k z xs)@, which avoids producing an intermediate list.
359 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
360 {-# INLINE [1] augment #-}
361 augment g xs = g (:) xs
364 "fold/build" forall k z (g::forall b. (a->b->b) -> b -> b) .
365 foldr k z (build g) = g k z
367 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) .
368 foldr k z (augment g xs) = g k (foldr k z xs)
370 "foldr/id" foldr (:) [] = \x -> x
371 "foldr/app" [1] forall ys. foldr (:) ys = \xs -> xs ++ ys
372 -- Only activate this from phase 1, because that's
373 -- when we disable the rule that expands (++) into foldr
375 -- The foldr/cons rule looks nice, but it can give disastrously
376 -- bloated code when commpiling
377 -- array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]
378 -- i.e. when there are very very long literal lists
379 -- So I've disabled it for now. We could have special cases
380 -- for short lists, I suppose.
381 -- "foldr/cons" forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)
383 "foldr/single" forall k z x. foldr k z [x] = k x z
384 "foldr/nil" forall k z. foldr k z [] = z
386 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)
387 (h::forall b. (a->b->b) -> b -> b) .
388 augment g (build h) = build (\c n -> g c (h c n))
389 "augment/nil" forall (g::forall b. (a->b->b) -> b -> b) .
390 augment g [] = build g
393 -- This rule is true, but not (I think) useful:
394 -- augment g (augment h t) = augment (\cn -> g c (h c n)) t
398 ----------------------------------------------
400 ----------------------------------------------
403 -- | 'map' @f xs@ is the list obtained by applying @f@ to each element
406 -- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
407 -- > map f [x1, x2, ...] == [f x1, f x2, ...]
409 map :: (a -> b) -> [a] -> [b]
411 map f (x:xs) = f x : map f xs
414 mapFB :: (elt -> lst -> lst) -> (a -> elt) -> a -> lst -> lst
415 {-# INLINE [0] mapFB #-}
416 mapFB c f x ys = c (f x) ys
418 -- The rules for map work like this.
420 -- Up to (but not including) phase 1, we use the "map" rule to
421 -- rewrite all saturated applications of map with its build/fold
422 -- form, hoping for fusion to happen.
423 -- In phase 1 and 0, we switch off that rule, inline build, and
424 -- switch on the "mapList" rule, which rewrites the foldr/mapFB
425 -- thing back into plain map.
427 -- It's important that these two rules aren't both active at once
428 -- (along with build's unfolding) else we'd get an infinite loop
429 -- in the rules. Hence the activation control below.
431 -- The "mapFB" rule optimises compositions of map.
433 -- This same pattern is followed by many other functions:
434 -- e.g. append, filter, iterate, repeat, etc.
437 "map" [~1] forall f xs. map f xs = build (\c n -> foldr (mapFB c f) n xs)
438 "mapList" [1] forall f. foldr (mapFB (:) f) [] = map f
439 "mapFB" forall c f g. mapFB (mapFB c f) g = mapFB c (f.g)
444 ----------------------------------------------
446 ----------------------------------------------
448 -- | Append two lists, i.e.,
450 -- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
451 -- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
453 -- If the first list is not finite, the result is the first list.
455 (++) :: [a] -> [a] -> [a]
457 (++) (x:xs) ys = x : xs ++ ys
460 "++" [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys
466 %*********************************************************
468 \subsection{Type @Bool@}
470 %*********************************************************
473 -- |The 'Bool' type is an enumeration. It is defined with 'False'
474 -- first so that the corresponding 'Prelude.Enum' instance will give
475 -- 'Prelude.fromEnum' 'False' the value zero, and
476 -- 'Prelude.fromEnum' 'True' the value 1.
477 -- The actual definition is in the ghc-prim package.
479 -- XXX These don't work:
480 -- deriving instance Eq Bool
481 -- deriving instance Ord Bool
482 -- <wired into compiler>:
483 -- Illegal binding of built-in syntax: con2tag_Bool#
485 instance Eq Bool where
487 False == False = True
490 instance Ord Bool where
491 compare False True = LT
492 compare True False = GT
495 -- Read is in GHC.Read, Show in GHC.Show
500 (&&) :: Bool -> Bool -> Bool
505 (||) :: Bool -> Bool -> Bool
514 -- |'otherwise' is defined as the value 'True'. It helps to make
515 -- guards more readable. eg.
517 -- > f x | x < 0 = ...
518 -- > | otherwise = ...
523 %*********************************************************
525 \subsection{The @()@ type}
527 %*********************************************************
529 The Unit type is here because virtually any program needs it (whereas
530 some programs may get away without consulting GHC.Tup). Furthermore,
531 the renamer currently *always* asks for () to be in scope, so that
532 ccalls can use () as their default type; so when compiling GHC.Base we
533 need (). (We could arrange suck in () only if -fglasgow-exts, but putting
534 it here seems more direct.)
537 -- | The unit datatype @()@ has one non-undefined member, the nullary
545 instance Ord () where
556 %*********************************************************
558 \subsection{Type @Ordering@}
560 %*********************************************************
563 -- | Represents an ordering relationship between two values: less
564 -- than, equal to, or greater than. An 'Ordering' is returned by
566 -- XXX These don't work:
567 -- deriving instance Eq Ordering
568 -- deriving instance Ord Ordering
569 -- Illegal binding of built-in syntax: con2tag_Ordering#
570 instance Eq Ordering where
575 -- Read in GHC.Read, Show in GHC.Show
577 instance Ord Ordering where
586 %*********************************************************
588 \subsection{Type @Char@ and @String@}
590 %*********************************************************
593 -- | A 'String' is a list of characters. String constants in Haskell are values
598 {-| The character type 'Char' is an enumeration whose values represent
599 Unicode (or equivalently ISO\/IEC 10646) characters
600 (see <http://www.unicode.org/> for details).
601 This set extends the ISO 8859-1 (Latin-1) character set
602 (the first 256 charachers), which is itself an extension of the ASCII
603 character set (the first 128 characters).
604 A character literal in Haskell has type 'Char'.
606 To convert a 'Char' to or from the corresponding 'Int' value defined
607 by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
608 'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
612 -- We don't use deriving for Eq and Ord, because for Ord the derived
613 -- instance defines only compare, which takes two primops. Then
614 -- '>' uses compare, and therefore takes two primops instead of one.
616 instance Eq Char where
617 (C# c1) == (C# c2) = c1 `eqChar#` c2
618 (C# c1) /= (C# c2) = c1 `neChar#` c2
620 instance Ord Char where
621 (C# c1) > (C# c2) = c1 `gtChar#` c2
622 (C# c1) >= (C# c2) = c1 `geChar#` c2
623 (C# c1) <= (C# c2) = c1 `leChar#` c2
624 (C# c1) < (C# c2) = c1 `ltChar#` c2
627 "x# `eqChar#` x#" forall x#. x# `eqChar#` x# = True
628 "x# `neChar#` x#" forall x#. x# `neChar#` x# = False
629 "x# `gtChar#` x#" forall x#. x# `gtChar#` x# = False
630 "x# `geChar#` x#" forall x#. x# `geChar#` x# = True
631 "x# `leChar#` x#" forall x#. x# `leChar#` x# = True
632 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
635 -- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
637 chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
638 | otherwise = error "Prelude.chr: bad argument"
640 unsafeChr :: Int -> Char
641 unsafeChr (I# i#) = C# (chr# i#)
643 -- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
645 ord (C# c#) = I# (ord# c#)
648 String equality is used when desugaring pattern-matches against strings.
651 eqString :: String -> String -> Bool
652 eqString [] [] = True
653 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
654 eqString cs1 cs2 = False
656 {-# RULES "eqString" (==) = eqString #-}
657 -- eqString also has a BuiltInRule in PrelRules.lhs:
658 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
662 %*********************************************************
664 \subsection{Type @Int@}
666 %*********************************************************
670 -- ^A fixed-precision integer type with at least the range @[-2^29 .. 2^29-1]@.
671 -- The exact range for a given implementation can be determined by using
672 -- 'Prelude.minBound' and 'Prelude.maxBound' from the 'Prelude.Bounded' class.
674 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
679 {- Seems clumsy. Should perhaps put minInt and MaxInt directly into MachDeps.h -}
680 #if WORD_SIZE_IN_BITS == 31
681 minInt = I# (-0x40000000#)
682 maxInt = I# 0x3FFFFFFF#
683 #elif WORD_SIZE_IN_BITS == 32
684 minInt = I# (-0x80000000#)
685 maxInt = I# 0x7FFFFFFF#
687 minInt = I# (-0x8000000000000000#)
688 maxInt = I# 0x7FFFFFFFFFFFFFFF#
691 instance Eq Int where
695 instance Ord Int where
702 compareInt :: Int -> Int -> Ordering
703 (I# x#) `compareInt` (I# y#) = compareInt# x# y#
705 compareInt# :: Int# -> Int# -> Ordering
713 %*********************************************************
715 \subsection{The function type}
717 %*********************************************************
720 -- | Identity function.
724 -- | The call '(lazy e)' means the same as 'e', but 'lazy' has a
725 -- magical strictness property: it is lazy in its first argument,
726 -- even though its semantics is strict.
729 -- Implementation note: its strictness and unfolding are over-ridden
730 -- by the definition in MkId.lhs; in both cases to nothing at all.
731 -- That way, 'lazy' does not get inlined, and the strictness analyser
732 -- sees it as lazy. Then the worker/wrapper phase inlines it.
736 -- | The call '(inline f)' reduces to 'f', but 'inline' has a BuiltInRule
737 -- that tries to inline 'f' (if it has an unfolding) unconditionally
738 -- The 'NOINLINE' pragma arranges that inline only gets inlined (and
739 -- hence eliminated) late in compilation, after the rule has had
740 -- a god chance to fire.
742 {-# NOINLINE[0] inline #-}
745 -- Assertion function. This simply ignores its boolean argument.
746 -- The compiler may rewrite it to @('assertError' line)@.
748 -- | If the first argument evaluates to 'True', then the result is the
749 -- second argument. Otherwise an 'AssertionFailed' exception is raised,
750 -- containing a 'String' with the source file and line number of the
753 -- Assertions can normally be turned on or off with a compiler flag
754 -- (for GHC, assertions are normally on unless optimisation is turned on
755 -- with @-O@ or the @-fignore-asserts@
756 -- option is given). When assertions are turned off, the first
757 -- argument to 'assert' is ignored, and the second argument is
758 -- returned as the result.
760 -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
761 -- but from Template Haskell onwards it's simply
762 -- defined here in Base.lhs
763 assert :: Bool -> a -> a
769 breakpointCond :: Bool -> a -> a
770 breakpointCond _ r = r
772 data Opaque = forall a. O a
774 -- | Constant function.
778 -- | Function composition.
780 (.) :: (b -> c) -> (a -> b) -> a -> c
783 -- | @'flip' f@ takes its (first) two arguments in the reverse order of @f@.
784 flip :: (a -> b -> c) -> b -> a -> c
787 -- | Application operator. This operator is redundant, since ordinary
788 -- application @(f x)@ means the same as @(f '$' x)@. However, '$' has
789 -- low, right-associative binding precedence, so it sometimes allows
790 -- parentheses to be omitted; for example:
792 -- > f $ g $ h x = f (g (h x))
794 -- It is also useful in higher-order situations, such as @'map' ('$' 0) xs@,
795 -- or @'Data.List.zipWith' ('$') fs xs@.
797 ($) :: (a -> b) -> a -> b
800 -- | @'until' p f@ yields the result of applying @f@ until @p@ holds.
801 until :: (a -> Bool) -> (a -> a) -> a -> a
802 until p f x | p x = x
803 | otherwise = until p f (f x)
805 -- | 'asTypeOf' is a type-restricted version of 'const'. It is usually
806 -- used as an infix operator, and its typing forces its first argument
807 -- (which is usually overloaded) to have the same type as the second.
808 asTypeOf :: a -> a -> a
812 %*********************************************************
814 \subsection{@getTag@}
816 %*********************************************************
818 Returns the 'tag' of a constructor application; this function is used
819 by the deriving code for Eq, Ord and Enum.
821 The primitive dataToTag# requires an evaluated constructor application
822 as its argument, so we provide getTag as a wrapper that performs the
823 evaluation before calling dataToTag#. We could have dataToTag#
824 evaluate its argument, but we prefer to do it this way because (a)
825 dataToTag# can be an inline primop if it doesn't need to do any
826 evaluation, and (b) we want to expose the evaluation to the
827 simplifier, because it might be possible to eliminate the evaluation
828 in the case when the argument is already known to be evaluated.
831 {-# INLINE getTag #-}
833 getTag x = x `seq` dataToTag# x
836 %*********************************************************
838 \subsection{Numeric primops}
840 %*********************************************************
843 divInt# :: Int# -> Int# -> Int#
845 -- Be careful NOT to overflow if we do any additional arithmetic
846 -- on the arguments... the following previous version of this
847 -- code has problems with overflow:
848 -- | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
849 -- | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
850 | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
851 | (x# <# 0#) && (y# ># 0#) = ((x# +# 1#) `quotInt#` y#) -# 1#
852 | otherwise = x# `quotInt#` y#
854 modInt# :: Int# -> Int# -> Int#
856 | (x# ># 0#) && (y# <# 0#) ||
857 (x# <# 0#) && (y# ># 0#) = if r# /=# 0# then r# +# y# else 0#
863 Definitions of the boxed PrimOps; these will be
864 used in the case of partial applications, etc.
873 {-# INLINE plusInt #-}
874 {-# INLINE minusInt #-}
875 {-# INLINE timesInt #-}
876 {-# INLINE quotInt #-}
877 {-# INLINE remInt #-}
878 {-# INLINE negateInt #-}
880 plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt, gcdInt :: Int -> Int -> Int
881 (I# x) `plusInt` (I# y) = I# (x +# y)
882 (I# x) `minusInt` (I# y) = I# (x -# y)
883 (I# x) `timesInt` (I# y) = I# (x *# y)
884 (I# x) `quotInt` (I# y) = I# (x `quotInt#` y)
885 (I# x) `remInt` (I# y) = I# (x `remInt#` y)
886 (I# x) `divInt` (I# y) = I# (x `divInt#` y)
887 (I# x) `modInt` (I# y) = I# (x `modInt#` y)
890 "x# +# 0#" forall x#. x# +# 0# = x#
891 "0# +# x#" forall x#. 0# +# x# = x#
892 "x# -# 0#" forall x#. x# -# 0# = x#
893 "x# -# x#" forall x#. x# -# x# = 0#
894 "x# *# 0#" forall x#. x# *# 0# = 0#
895 "0# *# x#" forall x#. 0# *# x# = 0#
896 "x# *# 1#" forall x#. x# *# 1# = x#
897 "1# *# x#" forall x#. 1# *# x# = x#
900 gcdInt (I# a) (I# b) = g a b
901 where g 0# 0# = error "GHC.Base.gcdInt: gcd 0 0 is undefined"
904 g _ _ = I# (gcdInt# absA absB)
906 absInt x = if x <# 0# then negateInt# x else x
911 negateInt :: Int -> Int
912 negateInt (I# x) = I# (negateInt# x)
914 gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
915 (I# x) `gtInt` (I# y) = x ># y
916 (I# x) `geInt` (I# y) = x >=# y
917 (I# x) `eqInt` (I# y) = x ==# y
918 (I# x) `neInt` (I# y) = x /=# y
919 (I# x) `ltInt` (I# y) = x <# y
920 (I# x) `leInt` (I# y) = x <=# y
923 "x# ># x#" forall x#. x# ># x# = False
924 "x# >=# x#" forall x#. x# >=# x# = True
925 "x# ==# x#" forall x#. x# ==# x# = True
926 "x# /=# x#" forall x#. x# /=# x# = False
927 "x# <# x#" forall x#. x# <# x# = False
928 "x# <=# x#" forall x#. x# <=# x# = True
932 "plusFloat x 0.0" forall x#. plusFloat# x# 0.0# = x#
933 "plusFloat 0.0 x" forall x#. plusFloat# 0.0# x# = x#
934 "minusFloat x 0.0" forall x#. minusFloat# x# 0.0# = x#
935 "minusFloat x x" forall x#. minusFloat# x# x# = 0.0#
936 "timesFloat x 0.0" forall x#. timesFloat# x# 0.0# = 0.0#
937 "timesFloat0.0 x" forall x#. timesFloat# 0.0# x# = 0.0#
938 "timesFloat x 1.0" forall x#. timesFloat# x# 1.0# = x#
939 "timesFloat 1.0 x" forall x#. timesFloat# 1.0# x# = x#
940 "divideFloat x 1.0" forall x#. divideFloat# x# 1.0# = x#
944 "plusDouble x 0.0" forall x#. (+##) x# 0.0## = x#
945 "plusDouble 0.0 x" forall x#. (+##) 0.0## x# = x#
946 "minusDouble x 0.0" forall x#. (-##) x# 0.0## = x#
947 "timesDouble x 1.0" forall x#. (*##) x# 1.0## = x#
948 "timesDouble 1.0 x" forall x#. (*##) 1.0## x# = x#
949 "divideDouble x 1.0" forall x#. (/##) x# 1.0## = x#
953 We'd like to have more rules, but for example:
955 This gives wrong answer (0) for NaN - NaN (should be NaN):
956 "minusDouble x x" forall x#. (-##) x# x# = 0.0##
958 This gives wrong answer (0) for 0 * NaN (should be NaN):
959 "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
961 This gives wrong answer (0) for NaN * 0 (should be NaN):
962 "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
964 These are tested by num014.
967 -- Wrappers for the shift operations. The uncheckedShift# family are
968 -- undefined when the amount being shifted by is greater than the size
969 -- in bits of Int#, so these wrappers perform a check and return
970 -- either zero or -1 appropriately.
972 -- Note that these wrappers still produce undefined results when the
973 -- second argument (the shift amount) is negative.
975 -- | Shift the argument left by the specified number of bits
976 -- (which must be non-negative).
977 shiftL# :: Word# -> Int# -> Word#
978 a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
979 | otherwise = a `uncheckedShiftL#` b
981 -- | Shift the argument right by the specified number of bits
982 -- (which must be non-negative).
983 shiftRL# :: Word# -> Int# -> Word#
984 a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
985 | otherwise = a `uncheckedShiftRL#` b
987 -- | Shift the argument left by the specified number of bits
988 -- (which must be non-negative).
989 iShiftL# :: Int# -> Int# -> Int#
990 a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
991 | otherwise = a `uncheckedIShiftL#` b
993 -- | Shift the argument right (signed) by the specified number of bits
994 -- (which must be non-negative).
995 iShiftRA# :: Int# -> Int# -> Int#
996 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
997 | otherwise = a `uncheckedIShiftRA#` b
999 -- | Shift the argument right (unsigned) by the specified number of bits
1000 -- (which must be non-negative).
1001 iShiftRL# :: Int# -> Int# -> Int#
1002 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
1003 | otherwise = a `uncheckedIShiftRL#` b
1005 #if WORD_SIZE_IN_BITS == 32
1007 "narrow32Int#" forall x#. narrow32Int# x# = x#
1008 "narrow32Word#" forall x#. narrow32Word# x# = x#
1013 "int2Word2Int" forall x#. int2Word# (word2Int# x#) = x#
1014 "word2Int2Word" forall x#. word2Int# (int2Word# x#) = x#
1019 %********************************************************
1021 \subsection{Unpacking C strings}
1023 %********************************************************
1025 This code is needed for virtually all programs, since it's used for
1026 unpacking the strings of error messages.
1029 unpackCString# :: Addr# -> [Char]
1030 {-# NOINLINE [1] unpackCString# #-}
1035 | ch `eqChar#` '\0'# = []
1036 | otherwise = C# ch : unpack (nh +# 1#)
1038 ch = indexCharOffAddr# addr nh
1040 unpackAppendCString# :: Addr# -> [Char] -> [Char]
1041 unpackAppendCString# addr rest
1045 | ch `eqChar#` '\0'# = rest
1046 | otherwise = C# ch : unpack (nh +# 1#)
1048 ch = indexCharOffAddr# addr nh
1050 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
1051 {-# NOINLINE [0] unpackFoldrCString# #-}
1052 -- Don't inline till right at the end;
1053 -- usually the unpack-list rule turns it into unpackCStringList
1054 -- It also has a BuiltInRule in PrelRules.lhs:
1055 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n)
1056 -- = unpackFoldrCString# "foobaz" c n
1057 unpackFoldrCString# addr f z
1061 | ch `eqChar#` '\0'# = z
1062 | otherwise = C# ch `f` unpack (nh +# 1#)
1064 ch = indexCharOffAddr# addr nh
1066 unpackCStringUtf8# :: Addr# -> [Char]
1067 unpackCStringUtf8# addr
1071 | ch `eqChar#` '\0'# = []
1072 | ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
1073 | ch `leChar#` '\xDF'# =
1074 C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
1075 (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
1077 | ch `leChar#` '\xEF'# =
1078 C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
1079 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
1080 (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
1083 C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
1084 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
1085 ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
1086 (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
1089 ch = indexCharOffAddr# addr nh
1091 unpackNBytes# :: Addr# -> Int# -> [Char]
1092 unpackNBytes# _addr 0# = []
1093 unpackNBytes# addr len# = unpack [] (len# -# 1#)
1098 case indexCharOffAddr# addr i# of
1099 ch -> unpack (C# ch : acc) (i# -# 1#)
1102 "unpack" [~1] forall a . unpackCString# a = build (unpackFoldrCString# a)
1103 "unpack-list" [1] forall a . unpackFoldrCString# a (:) [] = unpackCString# a
1104 "unpack-append" forall a n . unpackFoldrCString# a (:) n = unpackAppendCString# a n
1106 -- There's a built-in rule (in PrelRules.lhs) for
1107 -- unpackFoldr "foo" c (unpackFoldr "baz" c n) = unpackFoldr "foobaz" c n
1114 -- | A special argument for the 'Control.Monad.ST.ST' type constructor,
1115 -- indexing a state embedded in the 'Prelude.IO' monad by
1116 -- 'Control.Monad.ST.stToIO'.