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_GHC -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 -----------------------------------------------------------------------------
88 module GHC.Prim, -- Re-export GHC.Prim and GHC.Err, to avoid lots
89 module GHC.Err -- of people having to import it explicitly
94 import {-# SOURCE #-} GHC.Err
98 infix 4 ==, /=, <, <=, >=, >
104 default () -- Double isn't available yet
108 %*********************************************************
110 \subsection{DEBUGGING STUFF}
111 %* (for use when compiling GHC.Base itself doesn't work)
113 %*********************************************************
117 data Bool = False | True
118 data Ordering = LT | EQ | GT
126 (&&) True True = True
132 unpackCString# :: Addr# -> [Char]
133 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
134 unpackAppendCString# :: Addr# -> [Char] -> [Char]
135 unpackCStringUtf8# :: Addr# -> [Char]
136 unpackCString# a = error "urk"
137 unpackFoldrCString# a = error "urk"
138 unpackAppendCString# a = error "urk"
139 unpackCStringUtf8# a = error "urk"
144 %*********************************************************
146 \subsection{Standard classes @Eq@, @Ord@}
148 %*********************************************************
152 -- | The 'Eq' class defines equality ('==') and inequality ('/=').
153 -- All the basic datatypes exported by the "Prelude" are instances of 'Eq',
154 -- and 'Eq' may be derived for any datatype whose constituents are also
155 -- instances of 'Eq'.
157 -- Minimal complete definition: either '==' or '/='.
160 (==), (/=) :: a -> a -> Bool
162 x /= y = not (x == y)
163 x == y = not (x /= y)
165 -- | The 'Ord' class is used for totally ordered datatypes.
167 -- Instances of 'Ord' can be derived for any user-defined
168 -- datatype whose constituent types are in 'Ord'. The declared order
169 -- of the constructors in the data declaration determines the ordering
170 -- in derived 'Ord' instances. The 'Ordering' datatype allows a single
171 -- comparison to determine the precise ordering of two objects.
173 -- Minimal complete definition: either 'compare' or '<='.
174 -- Using 'compare' can be more efficient for complex types.
176 class (Eq a) => Ord a where
177 compare :: a -> a -> Ordering
178 (<), (<=), (>), (>=) :: a -> a -> Bool
179 max, min :: a -> a -> a
183 | x <= y = LT -- NB: must be '<=' not '<' to validate the
184 -- above claim about the minimal things that
185 -- can be defined for an instance of Ord
188 x < y = case compare x y of { LT -> True; _other -> False }
189 x <= y = case compare x y of { GT -> False; _other -> True }
190 x > y = case compare x y of { GT -> True; _other -> False }
191 x >= y = case compare x y of { LT -> False; _other -> True }
193 -- These two default methods use '<=' rather than 'compare'
194 -- because the latter is often more expensive
195 max x y = if x <= y then y else x
196 min x y = if x <= y then x else y
199 %*********************************************************
201 \subsection{Monadic classes @Functor@, @Monad@ }
203 %*********************************************************
206 {- | The 'Functor' class is used for types that can be mapped over.
207 Instances of 'Functor' should satisfy the following laws:
210 > fmap (f . g) == fmap f . fmap g
212 The instances of 'Functor' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
213 defined in the "Prelude" satisfy these laws.
216 class Functor f where
217 fmap :: (a -> b) -> f a -> f b
219 {- | The 'Monad' class defines the basic operations over a /monad/,
220 a concept from a branch of mathematics known as /category theory/.
221 From the perspective of a Haskell programmer, however, it is best to
222 think of a monad as an /abstract datatype/ of actions.
223 Haskell's @do@ expressions provide a convenient syntax for writing
226 Minimal complete definition: '>>=' and 'return'.
228 Instances of 'Monad' should satisfy the following laws:
230 > return a >>= k == k a
232 > m >>= (\x -> k x >>= h) == (m >>= k) >>= h
234 Instances of both 'Monad' and 'Functor' should additionally satisfy the law:
236 > fmap f xs == xs >>= return . f
238 The instances of 'Monad' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
239 defined in the "Prelude" satisfy these laws.
243 -- | Sequentially compose two actions, passing any value produced
244 -- by the first as an argument to the second.
245 (>>=) :: forall a b. m a -> (a -> m b) -> m b
246 -- | Sequentially compose two actions, discarding any value produced
247 -- by the first, like sequencing operators (such as the semicolon)
248 -- in imperative languages.
249 (>>) :: forall a b. m a -> m b -> m b
250 -- Explicit for-alls so that we know what order to
251 -- give type arguments when desugaring
253 -- | Inject a value into the monadic type.
255 -- | Fail with a message. This operation is not part of the
256 -- mathematical definition of a monad, but is invoked on pattern-match
257 -- failure in a @do@ expression.
258 fail :: String -> m a
260 m >> k = m >>= \_ -> k
265 %*********************************************************
267 \subsection{The list type}
269 %*********************************************************
272 data [] a = [] | a : [a] -- do explicitly: deriving (Eq, Ord)
273 -- to avoid weird names like con2tag_[]#
276 instance (Eq a) => Eq [a] where
277 {-# SPECIALISE instance Eq [Char] #-}
279 (x:xs) == (y:ys) = x == y && xs == ys
282 instance (Ord a) => Ord [a] where
283 {-# SPECIALISE instance Ord [Char] #-}
285 compare [] (_:_) = LT
286 compare (_:_) [] = GT
287 compare (x:xs) (y:ys) = case compare x y of
291 instance Functor [] where
294 instance Monad [] where
295 m >>= k = foldr ((++) . k) [] m
296 m >> k = foldr ((++) . (\ _ -> k)) [] m
301 A few list functions that appear here because they are used here.
302 The rest of the prelude list functions are in GHC.List.
304 ----------------------------------------------
305 -- foldr/build/augment
306 ----------------------------------------------
309 -- | 'foldr', applied to a binary operator, a starting value (typically
310 -- the right-identity of the operator), and a list, reduces the list
311 -- using the binary operator, from right to left:
313 -- > foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
315 foldr :: (a -> b -> b) -> b -> [a] -> b
317 -- foldr f z (x:xs) = f x (foldr f z xs)
318 {-# INLINE [0] foldr #-}
319 -- Inline only in the final stage, after the foldr/cons rule has had a chance
323 go (y:ys) = y `k` go ys
325 -- | A list producer that can be fused with 'foldr'.
326 -- This function is merely
328 -- > build g = g (:) []
330 -- but GHC's simplifier will transform an expression of the form
331 -- @'foldr' k z ('build' g)@, which may arise after inlining, to @g k z@,
332 -- which avoids producing an intermediate list.
334 build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
335 {-# INLINE [1] build #-}
336 -- The INLINE is important, even though build is tiny,
337 -- because it prevents [] getting inlined in the version that
338 -- appears in the interface file. If [] *is* inlined, it
339 -- won't match with [] appearing in rules in an importing module.
341 -- The "1" says to inline in phase 1
345 -- | A list producer that can be fused with 'foldr'.
346 -- This function is merely
348 -- > augment g xs = g (:) xs
350 -- but GHC's simplifier will transform an expression of the form
351 -- @'foldr' k z ('augment' g xs)@, which may arise after inlining, to
352 -- @g k ('foldr' k z xs)@, which avoids producing an intermediate list.
354 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
355 {-# INLINE [1] augment #-}
356 augment g xs = g (:) xs
359 "fold/build" forall k z (g::forall b. (a->b->b) -> b -> b) .
360 foldr k z (build g) = g k z
362 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) .
363 foldr k z (augment g xs) = g k (foldr k z xs)
365 "foldr/id" foldr (:) [] = \x -> x
366 "foldr/app" [1] forall ys. foldr (:) ys = \xs -> xs ++ ys
367 -- Only activate this from phase 1, because that's
368 -- when we disable the rule that expands (++) into foldr
370 -- The foldr/cons rule looks nice, but it can give disastrously
371 -- bloated code when commpiling
372 -- array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]
373 -- i.e. when there are very very long literal lists
374 -- So I've disabled it for now. We could have special cases
375 -- for short lists, I suppose.
376 -- "foldr/cons" forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)
378 "foldr/single" forall k z x. foldr k z [x] = k x z
379 "foldr/nil" forall k z. foldr k z [] = z
381 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)
382 (h::forall b. (a->b->b) -> b -> b) .
383 augment g (build h) = build (\c n -> g c (h c n))
384 "augment/nil" forall (g::forall b. (a->b->b) -> b -> b) .
385 augment g [] = build g
388 -- This rule is true, but not (I think) useful:
389 -- augment g (augment h t) = augment (\cn -> g c (h c n)) t
393 ----------------------------------------------
395 ----------------------------------------------
398 -- | 'map' @f xs@ is the list obtained by applying @f@ to each element
401 -- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
402 -- > map f [x1, x2, ...] == [f x1, f x2, ...]
404 map :: (a -> b) -> [a] -> [b]
406 map f (x:xs) = f x : map f xs
409 mapFB :: (elt -> lst -> lst) -> (a -> elt) -> a -> lst -> lst
410 {-# INLINE [0] mapFB #-}
411 mapFB c f x ys = c (f x) ys
413 -- The rules for map work like this.
415 -- Up to (but not including) phase 1, we use the "map" rule to
416 -- rewrite all saturated applications of map with its build/fold
417 -- form, hoping for fusion to happen.
418 -- In phase 1 and 0, we switch off that rule, inline build, and
419 -- switch on the "mapList" rule, which rewrites the foldr/mapFB
420 -- thing back into plain map.
422 -- It's important that these two rules aren't both active at once
423 -- (along with build's unfolding) else we'd get an infinite loop
424 -- in the rules. Hence the activation control below.
426 -- The "mapFB" rule optimises compositions of map.
428 -- This same pattern is followed by many other functions:
429 -- e.g. append, filter, iterate, repeat, etc.
432 "map" [~1] forall f xs. map f xs = build (\c n -> foldr (mapFB c f) n xs)
433 "mapList" [1] forall f. foldr (mapFB (:) f) [] = map f
434 "mapFB" forall c f g. mapFB (mapFB c f) g = mapFB c (f.g)
439 ----------------------------------------------
441 ----------------------------------------------
443 -- | Append two lists, i.e.,
445 -- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
446 -- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
448 -- If the first list is not finite, the result is the first list.
450 (++) :: [a] -> [a] -> [a]
452 (++) (x:xs) ys = x : xs ++ ys
455 "++" [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys
461 %*********************************************************
463 \subsection{Type @Bool@}
465 %*********************************************************
468 -- |The 'Bool' type is an enumeration. It is defined with 'False'
469 -- first so that the corresponding 'Prelude.Enum' instance will give
470 -- 'Prelude.fromEnum' 'False' the value zero, and
471 -- 'Prelude.fromEnum' 'True' the value 1.
472 data Bool = False | True deriving (Eq, Ord)
473 -- Read in GHC.Read, Show in GHC.Show
478 (&&) :: Bool -> Bool -> Bool
483 (||) :: Bool -> Bool -> Bool
492 -- |'otherwise' is defined as the value 'True'. It helps to make
493 -- guards more readable. eg.
495 -- > f x | x < 0 = ...
496 -- > | otherwise = ...
502 %*********************************************************
504 \subsection{The @()@ type}
506 %*********************************************************
508 The Unit type is here because virtually any program needs it (whereas
509 some programs may get away without consulting GHC.Tup). Furthermore,
510 the renamer currently *always* asks for () to be in scope, so that
511 ccalls can use () as their default type; so when compiling GHC.Base we
512 need (). (We could arrange suck in () only if -fglasgow-exts, but putting
513 it here seems more direct.)
516 -- | The unit datatype @()@ has one non-undefined member, the nullary
524 instance Ord () where
535 %*********************************************************
537 \subsection{Type @Ordering@}
539 %*********************************************************
542 -- | Represents an ordering relationship between two values: less
543 -- than, equal to, or greater than. An 'Ordering' is returned by
545 data Ordering = LT | EQ | GT deriving (Eq, Ord)
546 -- Read in GHC.Read, Show in GHC.Show
550 %*********************************************************
552 \subsection{Type @Char@ and @String@}
554 %*********************************************************
557 -- | A 'String' is a list of characters. String constants in Haskell are values
562 {-| The character type 'Char' is an enumeration whose values represent
563 Unicode (or equivalently ISO\/IEC 10646) characters
564 (see <http://www.unicode.org/> for details).
565 This set extends the ISO 8859-1 (Latin-1) character set
566 (the first 256 charachers), which is itself an extension of the ASCII
567 character set (the first 128 characters).
568 A character literal in Haskell has type 'Char'.
570 To convert a 'Char' to or from the corresponding 'Int' value defined
571 by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
572 'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
576 -- We don't use deriving for Eq and Ord, because for Ord the derived
577 -- instance defines only compare, which takes two primops. Then
578 -- '>' uses compare, and therefore takes two primops instead of one.
580 instance Eq Char where
581 (C# c1) == (C# c2) = c1 `eqChar#` c2
582 (C# c1) /= (C# c2) = c1 `neChar#` c2
584 instance Ord Char where
585 (C# c1) > (C# c2) = c1 `gtChar#` c2
586 (C# c1) >= (C# c2) = c1 `geChar#` c2
587 (C# c1) <= (C# c2) = c1 `leChar#` c2
588 (C# c1) < (C# c2) = c1 `ltChar#` c2
591 "x# `eqChar#` x#" forall x#. x# `eqChar#` x# = True
592 "x# `neChar#` x#" forall x#. x# `neChar#` x# = False
593 "x# `gtChar#` x#" forall x#. x# `gtChar#` x# = False
594 "x# `geChar#` x#" forall x#. x# `geChar#` x# = True
595 "x# `leChar#` x#" forall x#. x# `leChar#` x# = True
596 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
599 -- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
601 chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
602 | otherwise = error "Prelude.chr: bad argument"
604 unsafeChr :: Int -> Char
605 unsafeChr (I# i#) = C# (chr# i#)
607 -- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
609 ord (C# c#) = I# (ord# c#)
612 String equality is used when desugaring pattern-matches against strings.
615 eqString :: String -> String -> Bool
616 eqString [] [] = True
617 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
618 eqString cs1 cs2 = False
620 {-# RULES "eqString" (==) = eqString #-}
621 -- eqString also has a BuiltInRule in PrelRules.lhs:
622 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
626 %*********************************************************
628 \subsection{Type @Int@}
630 %*********************************************************
634 -- ^A fixed-precision integer type with at least the range @[-2^29 .. 2^29-1]@.
635 -- The exact range for a given implementation can be determined by using
636 -- 'Prelude.minBound' and 'Prelude.maxBound' from the 'Prelude.Bounded' class.
638 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
643 {- Seems clumsy. Should perhaps put minInt and MaxInt directly into MachDeps.h -}
644 #if WORD_SIZE_IN_BITS == 31
645 minInt = I# (-0x40000000#)
646 maxInt = I# 0x3FFFFFFF#
647 #elif WORD_SIZE_IN_BITS == 32
648 minInt = I# (-0x80000000#)
649 maxInt = I# 0x7FFFFFFF#
651 minInt = I# (-0x8000000000000000#)
652 maxInt = I# 0x7FFFFFFFFFFFFFFF#
655 instance Eq Int where
659 instance Ord Int where
666 compareInt :: Int -> Int -> Ordering
667 (I# x#) `compareInt` (I# y#) = compareInt# x# y#
669 compareInt# :: Int# -> Int# -> Ordering
677 %*********************************************************
679 \subsection{The function type}
681 %*********************************************************
684 -- | Identity function.
688 -- | The call '(lazy e)' means the same as 'e', but 'lazy' has a
689 -- magical strictness property: it is lazy in its first argument,
690 -- even though its semantics is strict.
693 -- Implementation note: its strictness and unfolding are over-ridden
694 -- by the definition in MkId.lhs; in both cases to nothing at all.
695 -- That way, 'lazy' does not get inlined, and the strictness analyser
696 -- sees it as lazy. Then the worker/wrapper phase inlines it.
700 -- | The call '(inline f)' reduces to 'f', but 'inline' has a BuiltInRule
701 -- that tries to inline 'f' (if it has an unfolding) unconditionally
702 -- The 'NOINLINE' pragma arranges that inline only gets inlined (and
703 -- hence eliminated) late in compilation, after the rule has had
704 -- a god chance to fire.
706 {-# NOINLINE[0] inline #-}
709 -- Assertion function. This simply ignores its boolean argument.
710 -- The compiler may rewrite it to @('assertError' line)@.
712 -- | If the first argument evaluates to 'True', then the result is the
713 -- second argument. Otherwise an 'AssertionFailed' exception is raised,
714 -- containing a 'String' with the source file and line number of the
717 -- Assertions can normally be turned on or off with a compiler flag
718 -- (for GHC, assertions are normally on unless optimisation is turned on
719 -- with @-O@ or the @-fignore-asserts@
720 -- option is given). When assertions are turned off, the first
721 -- argument to 'assert' is ignored, and the second argument is
722 -- returned as the result.
724 -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
725 -- but from Template Haskell onwards it's simply
726 -- defined here in Base.lhs
727 assert :: Bool -> a -> a
733 breakpointCond :: Bool -> a -> a
734 breakpointCond _ r = r
736 -- | Constant function.
740 -- | Function composition.
742 (.) :: (b -> c) -> (a -> b) -> a -> c
745 -- | @'flip' f@ takes its (first) two arguments in the reverse order of @f@.
746 flip :: (a -> b -> c) -> b -> a -> c
749 -- | Application operator. This operator is redundant, since ordinary
750 -- application @(f x)@ means the same as @(f '$' x)@. However, '$' has
751 -- low, right-associative binding precedence, so it sometimes allows
752 -- parentheses to be omitted; for example:
754 -- > f $ g $ h x = f (g (h x))
756 -- It is also useful in higher-order situations, such as @'map' ('$' 0) xs@,
757 -- or @'Data.List.zipWith' ('$') fs xs@.
759 ($) :: (a -> b) -> a -> b
762 -- | @'until' p f@ yields the result of applying @f@ until @p@ holds.
763 until :: (a -> Bool) -> (a -> a) -> a -> a
764 until p f x | p x = x
765 | otherwise = until p f (f x)
767 -- | 'asTypeOf' is a type-restricted version of 'const'. It is usually
768 -- used as an infix operator, and its typing forces its first argument
769 -- (which is usually overloaded) to have the same type as the second.
770 asTypeOf :: a -> a -> a
774 %*********************************************************
776 \subsection{Generics}
778 %*********************************************************
783 data (:+:) a b = Inl a | Inr b
784 data (:*:) a b = a :*: b
788 %*********************************************************
790 \subsection{@getTag@}
792 %*********************************************************
794 Returns the 'tag' of a constructor application; this function is used
795 by the deriving code for Eq, Ord and Enum.
797 The primitive dataToTag# requires an evaluated constructor application
798 as its argument, so we provide getTag as a wrapper that performs the
799 evaluation before calling dataToTag#. We could have dataToTag#
800 evaluate its argument, but we prefer to do it this way because (a)
801 dataToTag# can be an inline primop if it doesn't need to do any
802 evaluation, and (b) we want to expose the evaluation to the
803 simplifier, because it might be possible to eliminate the evaluation
804 in the case when the argument is already known to be evaluated.
807 {-# INLINE getTag #-}
809 getTag x = x `seq` dataToTag# x
812 %*********************************************************
814 \subsection{Numeric primops}
816 %*********************************************************
819 divInt# :: Int# -> Int# -> Int#
821 -- Be careful NOT to overflow if we do any additional arithmetic
822 -- on the arguments... the following previous version of this
823 -- code has problems with overflow:
824 -- | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
825 -- | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
826 | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
827 | (x# <# 0#) && (y# ># 0#) = ((x# +# 1#) `quotInt#` y#) -# 1#
828 | otherwise = x# `quotInt#` y#
830 modInt# :: Int# -> Int# -> Int#
832 | (x# ># 0#) && (y# <# 0#) ||
833 (x# <# 0#) && (y# ># 0#) = if r# /=# 0# then r# +# y# else 0#
839 Definitions of the boxed PrimOps; these will be
840 used in the case of partial applications, etc.
849 {-# INLINE plusInt #-}
850 {-# INLINE minusInt #-}
851 {-# INLINE timesInt #-}
852 {-# INLINE quotInt #-}
853 {-# INLINE remInt #-}
854 {-# INLINE negateInt #-}
856 plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt, gcdInt :: Int -> Int -> Int
857 (I# x) `plusInt` (I# y) = I# (x +# y)
858 (I# x) `minusInt` (I# y) = I# (x -# y)
859 (I# x) `timesInt` (I# y) = I# (x *# y)
860 (I# x) `quotInt` (I# y) = I# (x `quotInt#` y)
861 (I# x) `remInt` (I# y) = I# (x `remInt#` y)
862 (I# x) `divInt` (I# y) = I# (x `divInt#` y)
863 (I# x) `modInt` (I# y) = I# (x `modInt#` y)
866 "x# +# 0#" forall x#. x# +# 0# = x#
867 "0# +# x#" forall x#. 0# +# x# = x#
868 "x# -# 0#" forall x#. x# -# 0# = x#
869 "x# -# x#" forall x#. x# -# x# = 0#
870 "x# *# 0#" forall x#. x# *# 0# = 0#
871 "0# *# x#" forall x#. 0# *# x# = 0#
872 "x# *# 1#" forall x#. x# *# 1# = x#
873 "1# *# x#" forall x#. 1# *# x# = x#
876 gcdInt (I# a) (I# b) = g a b
877 where g 0# 0# = error "GHC.Base.gcdInt: gcd 0 0 is undefined"
880 g _ _ = I# (gcdInt# absA absB)
882 absInt x = if x <# 0# then negateInt# x else x
887 negateInt :: Int -> Int
888 negateInt (I# x) = I# (negateInt# x)
890 gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
891 (I# x) `gtInt` (I# y) = x ># y
892 (I# x) `geInt` (I# y) = x >=# y
893 (I# x) `eqInt` (I# y) = x ==# y
894 (I# x) `neInt` (I# y) = x /=# y
895 (I# x) `ltInt` (I# y) = x <# y
896 (I# x) `leInt` (I# y) = x <=# y
899 "x# ># x#" forall x#. x# ># x# = False
900 "x# >=# x#" forall x#. x# >=# x# = True
901 "x# ==# x#" forall x#. x# ==# x# = True
902 "x# /=# x#" forall x#. x# /=# x# = False
903 "x# <# x#" forall x#. x# <# x# = False
904 "x# <=# x#" forall x#. x# <=# x# = True
908 "plusFloat x 0.0" forall x#. plusFloat# x# 0.0# = x#
909 "plusFloat 0.0 x" forall x#. plusFloat# 0.0# x# = x#
910 "minusFloat x 0.0" forall x#. minusFloat# x# 0.0# = x#
911 "minusFloat x x" forall x#. minusFloat# x# x# = 0.0#
912 "timesFloat x 0.0" forall x#. timesFloat# x# 0.0# = 0.0#
913 "timesFloat0.0 x" forall x#. timesFloat# 0.0# x# = 0.0#
914 "timesFloat x 1.0" forall x#. timesFloat# x# 1.0# = x#
915 "timesFloat 1.0 x" forall x#. timesFloat# 1.0# x# = x#
916 "divideFloat x 1.0" forall x#. divideFloat# x# 1.0# = x#
920 "plusDouble x 0.0" forall x#. (+##) x# 0.0## = x#
921 "plusDouble 0.0 x" forall x#. (+##) 0.0## x# = x#
922 "minusDouble x 0.0" forall x#. (-##) x# 0.0## = x#
923 "minusDouble x x" forall x#. (-##) x# x# = 0.0##
924 "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
925 "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
926 "timesDouble x 1.0" forall x#. (*##) x# 1.0## = x#
927 "timesDouble 1.0 x" forall x#. (*##) 1.0## x# = x#
928 "divideDouble x 1.0" forall x#. (/##) x# 1.0## = x#
931 -- Wrappers for the shift operations. The uncheckedShift# family are
932 -- undefined when the amount being shifted by is greater than the size
933 -- in bits of Int#, so these wrappers perform a check and return
934 -- either zero or -1 appropriately.
936 -- Note that these wrappers still produce undefined results when the
937 -- second argument (the shift amount) is negative.
939 -- | Shift the argument left by the specified number of bits
940 -- (which must be non-negative).
941 shiftL# :: Word# -> Int# -> Word#
942 a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
943 | otherwise = a `uncheckedShiftL#` b
945 -- | Shift the argument right by the specified number of bits
946 -- (which must be non-negative).
947 shiftRL# :: Word# -> Int# -> Word#
948 a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
949 | otherwise = a `uncheckedShiftRL#` b
951 -- | Shift the argument left by the specified number of bits
952 -- (which must be non-negative).
953 iShiftL# :: Int# -> Int# -> Int#
954 a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
955 | otherwise = a `uncheckedIShiftL#` b
957 -- | Shift the argument right (signed) by the specified number of bits
958 -- (which must be non-negative).
959 iShiftRA# :: Int# -> Int# -> Int#
960 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
961 | otherwise = a `uncheckedIShiftRA#` b
963 -- | Shift the argument right (unsigned) by the specified number of bits
964 -- (which must be non-negative).
965 iShiftRL# :: Int# -> Int# -> Int#
966 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
967 | otherwise = a `uncheckedIShiftRL#` b
969 #if WORD_SIZE_IN_BITS == 32
971 "narrow32Int#" forall x#. narrow32Int# x# = x#
972 "narrow32Word#" forall x#. narrow32Word# x# = x#
977 "int2Word2Int" forall x#. int2Word# (word2Int# x#) = x#
978 "word2Int2Word" forall x#. word2Int# (int2Word# x#) = x#
983 %********************************************************
985 \subsection{Unpacking C strings}
987 %********************************************************
989 This code is needed for virtually all programs, since it's used for
990 unpacking the strings of error messages.
993 unpackCString# :: Addr# -> [Char]
994 {-# NOINLINE [1] unpackCString# #-}
999 | ch `eqChar#` '\0'# = []
1000 | otherwise = C# ch : unpack (nh +# 1#)
1002 ch = indexCharOffAddr# addr nh
1004 unpackAppendCString# :: Addr# -> [Char] -> [Char]
1005 unpackAppendCString# addr rest
1009 | ch `eqChar#` '\0'# = rest
1010 | otherwise = C# ch : unpack (nh +# 1#)
1012 ch = indexCharOffAddr# addr nh
1014 unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a
1015 {-# NOINLINE [0] unpackFoldrCString# #-}
1016 -- Don't inline till right at the end;
1017 -- usually the unpack-list rule turns it into unpackCStringList
1018 -- It also has a BuiltInRule in PrelRules.lhs:
1019 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n)
1020 -- = unpackFoldrCString# "foobaz" c n
1021 unpackFoldrCString# addr f z
1025 | ch `eqChar#` '\0'# = z
1026 | otherwise = C# ch `f` unpack (nh +# 1#)
1028 ch = indexCharOffAddr# addr nh
1030 unpackCStringUtf8# :: Addr# -> [Char]
1031 unpackCStringUtf8# addr
1035 | ch `eqChar#` '\0'# = []
1036 | ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
1037 | ch `leChar#` '\xDF'# =
1038 C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
1039 (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
1041 | ch `leChar#` '\xEF'# =
1042 C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
1043 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
1044 (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
1047 C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
1048 ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
1049 ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
1050 (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
1053 ch = indexCharOffAddr# addr nh
1055 unpackNBytes# :: Addr# -> Int# -> [Char]
1056 unpackNBytes# _addr 0# = []
1057 unpackNBytes# addr len# = unpack [] (len# -# 1#)
1062 case indexCharOffAddr# addr i# of
1063 ch -> unpack (C# ch : acc) (i# -# 1#)
1066 "unpack" [~1] forall a . unpackCString# a = build (unpackFoldrCString# a)
1067 "unpack-list" [1] forall a . unpackFoldrCString# a (:) [] = unpackCString# a
1068 "unpack-append" forall a n . unpackFoldrCString# a (:) n = unpackAppendCString# a n
1070 -- There's a built-in rule (in PrelRules.lhs) for
1071 -- unpackFoldr "foo" c (unpackFoldr "baz" c n) = unpackFoldr "foobaz" c n
1078 -- | A special argument for the 'Control.Monad.ST.ST' type constructor,
1079 -- indexing a state embedded in the 'Prelude.IO' monad by
1080 -- 'Control.Monad.ST.stToIO'.