X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=GHC%2FBase.lhs;h=c590366b6829914b6139b3d99df8d902324cd431;hb=4b26136ab82fb1ff12e49477c4833a9586d368c5;hp=f957a6d55cffc743fe8d1285e5d8897e28feb369;hpb=69daab60bb6f89433a0394182481d721dc2f42fd;p=haskell-directory.git diff --git a/GHC/Base.lhs b/GHC/Base.lhs index f957a6d..c590366 100644 --- a/GHC/Base.lhs +++ b/GHC/Base.lhs @@ -16,12 +16,10 @@ GHC.Prim Has no implementation. It defines built-in things, and The source file is GHC.Prim.hi-boot, which is just copied to make GHC.Prim.hi - Classes: CCallable, CReturnable - GHC.Base Classes: Eq, Ord, Functor, Monad Types: list, (), Int, Bool, Ordering, Char, String -Data.Tup Types: tuples, plus instances for GHC.Base classes +Data.Tuple Types: tuples, plus instances for GHC.Base classes GHC.Show Class: Show, plus instances for GHC.Base/GHC.Tup types @@ -29,6 +27,8 @@ GHC.Enum Class: Enum, plus instances for GHC.Base/GHC.Tup types Data.Maybe Type: Maybe, plus instances for GHC.Base classes +GHC.List List functions + GHC.Num Class: Num, plus instances for Int Type: Integer, plus instances for all classes so far (Eq, Ord, Num, Show) @@ -43,11 +43,12 @@ GHC.Real Classes: Real, Integral, Fractional, RealFrac Rational is needed here because it is mentioned in the signature of 'toRational' in class Real +GHC.ST The ST monad, instances and a few helper functions + Ix Classes: Ix, plus instances for Int, Bool, Char, Integer, Ordering, tuples GHC.Arr Types: Array, MutableArray, MutableVar - Does *not* contain any ByteArray stuff (see GHC.ByteArr) Arrays are used by a function in GHC.Float GHC.Float Classes: Floating, RealFloat @@ -57,16 +58,11 @@ GHC.Float Classes: Floating, RealFloat It is a big module (900 lines) With a bit of luck, many modules can be compiled without ever reading GHC.Float.hi -GHC.ByteArr Types: ByteArray, MutableByteArray - - We want this one to be after GHC.Float, because it defines arrays - of unboxed floats. - Other Prelude modules are much easier with fewer complex dependencies. \begin{code} -{-# OPTIONS -fno-implicit-prelude #-} +{-# OPTIONS_GHC -fno-implicit-prelude #-} ----------------------------------------------------------------------------- -- | -- Module : GHC.Base @@ -83,6 +79,7 @@ Other Prelude modules are much easier with fewer complex dependencies. #include "MachDeps.h" +-- #hide module GHC.Base ( module GHC.Base, @@ -163,14 +160,22 @@ class Eq a where x /= y = not (x == y) x == y = not (x /= y) +-- | The 'Ord' class is used for totally ordered datatypes. +-- +-- Instances of 'Ord' can be derived for any user-defined +-- datatype whose constituent types are in 'Ord'. The declared order +-- of the constructors in the data declaration determines the ordering +-- in derived 'Ord' instances. The 'Ordering' datatype allows a single +-- comparison to determine the precise ordering of two objects. +-- +-- Minimal complete definition: either 'compare' or '<='. +-- Using 'compare' can be more efficient for complex types. +-- class (Eq a) => Ord a where compare :: a -> a -> Ordering (<), (<=), (>), (>=) :: a -> a -> Bool max, min :: a -> a -> a - -- An instance of Ord should define either 'compare' or '<='. - -- Using 'compare' can be more efficient for complex types. - compare x y | x == y = EQ | x <= y = LT -- NB: must be '<=' not '<' to validate the @@ -202,14 +207,22 @@ Instances of 'Functor' should satisfy the following laws: > fmap id == id > fmap (f . g) == fmap f . fmap g -The instances of 'Functor' for lists, 'Maybe' and 'IO' defined in the "Prelude" -satisfy these laws. +The instances of 'Functor' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO' +defined in the "Prelude" satisfy these laws. -} class Functor f where fmap :: (a -> b) -> f a -> f b -{- | The 'Monad' class defines the basic operations over a /monad/. +{- | The 'Monad' class defines the basic operations over a /monad/, +a concept from a branch of mathematics known as /category theory/. +From the perspective of a Haskell programmer, however, it is best to +think of a monad as an /abstract datatype/ of actions. +Haskell's @do@ expressions provide a convenient syntax for writing +monadic expressions. + +Minimal complete definition: '>>=' and 'return'. + Instances of 'Monad' should satisfy the following laws: > return a >>= k == k a @@ -220,14 +233,26 @@ Instances of both 'Monad' and 'Functor' should additionally satisfy the law: > fmap f xs == xs >>= return . f -The instances of 'Monad' for lists, 'Maybe' and 'IO' defined in the "Prelude" -satisfy these laws. +The instances of 'Monad' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO' +defined in the "Prelude" satisfy these laws. -} class Monad m where - (>>=) :: m a -> (a -> m b) -> m b - (>>) :: m a -> m b -> m b + -- | Sequentially compose two actions, passing any value produced + -- by the first as an argument to the second. + (>>=) :: forall a b. m a -> (a -> m b) -> m b + -- | Sequentially compose two actions, discarding any value produced + -- by the first, like sequencing operators (such as the semicolon) + -- in imperative languages. + (>>) :: forall a b. m a -> m b -> m b + -- Explicit for-alls so that we know what order to + -- give type arguments when desugaring + + -- | Inject a value into the monadic type. return :: a -> m a + -- | Fail with a message. This operation is not part of the + -- mathematical definition of a monad, but is invoked on pattern-match + -- failure in a @do@ expression. fail :: String -> m a m >> k = m >>= \_ -> k @@ -295,6 +320,15 @@ foldr k z xs = go xs go [] = z go (y:ys) = y `k` go ys +-- | A list producer that can be fused with 'foldr'. +-- This function is merely +-- +-- > build g = g (:) [] +-- +-- but GHC's simplifier will transform an expression of the form +-- @'foldr' k z ('build' g)@, which may arise after inlining, to @g k z@, +-- which avoids producing an intermediate list. + build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a] {-# INLINE [1] build #-} -- The INLINE is important, even though build is tiny, @@ -306,6 +340,15 @@ build :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a] build g = g (:) [] +-- | A list producer that can be fused with 'foldr'. +-- This function is merely +-- +-- > augment g xs = g (:) xs +-- +-- but GHC's simplifier will transform an expression of the form +-- @'foldr' k z ('augment' g xs)@, which may arise after inlining, to +-- @g k ('foldr' k z xs)@, which avoids producing an intermediate list. + augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a] {-# INLINE [1] augment #-} augment g xs = g (:) xs @@ -317,8 +360,8 @@ augment g xs = g (:) xs "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) . foldr k z (augment g xs) = g k (foldr k z xs) -"foldr/id" foldr (:) [] = \x->x -"foldr/app" [1] forall xs ys. foldr (:) ys xs = xs ++ ys +"foldr/id" foldr (:) [] = \x -> x +"foldr/app" [1] forall ys. foldr (:) ys = \xs -> xs ++ ys -- Only activate this from phase 1, because that's -- when we disable the rule that expands (++) into foldr @@ -453,7 +496,6 @@ otherwise :: Bool otherwise = True \end{code} - %********************************************************* %* * \subsection{The @()@ type} @@ -515,7 +557,8 @@ data Ordering = LT | EQ | GT deriving (Eq, Ord) type String = [Char] {-| The character type 'Char' is an enumeration whose values represent -Unicode (or equivalently ISO 10646) characters. +Unicode (or equivalently ISO\/IEC 10646) characters +(see for details). This set extends the ISO 8859-1 (Latin-1) character set (the first 256 charachers), which is itself an extension of the ASCII character set (the first 128 characters). @@ -572,6 +615,8 @@ eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2 eqString cs1 cs2 = False {-# RULES "eqString" (==) = eqString #-} +-- eqString also has a BuiltInRule in PrelRules.lhs: +-- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2 \end{code} @@ -583,10 +628,9 @@ eqString cs1 cs2 = False \begin{code} data Int = I# Int# --- ^A fixed-precision integer type with at least the range @[-2^29 --- .. 2^29-1]@. The exact range for a given implementation can be --- determined by using 'minBound' and 'maxBound' from the 'Bounded' --- class. +-- ^A fixed-precision integer type with at least the range @[-2^29 .. 2^29-1]@. +-- The exact range for a given implementation can be determined by using +-- 'Prelude.minBound' and 'Prelude.maxBound' from the 'Prelude.Bounded' class. zeroInt, oneInt, twoInt, maxInt, minInt :: Int zeroInt = I# 0# @@ -634,52 +678,99 @@ compareInt# x# y# %********************************************************* \begin{code} --- identity function +-- | Identity function. id :: a -> a id x = x --- lazy function; this is just the same as id, but its unfolding --- and strictness are over-ridden by the definition in MkId.lhs --- That way, it does not get inlined, and the strictness analyser --- sees it as lazy. Then the worker/wrapper phase inlines it. --- Result: happiness +-- | The call '(lazy e)' means the same as 'e', but 'lazy' has a +-- magical strictness property: it is lazy in its first argument, +-- even though its semantics is strict. lazy :: a -> a lazy x = x +-- Implementation note: its strictness and unfolding are over-ridden +-- by the definition in MkId.lhs; in both cases to nothing at all. +-- That way, 'lazy' does not get inlined, and the strictness analyser +-- sees it as lazy. Then the worker/wrapper phase inlines it. +-- Result: happiness + + +-- | The call '(inline f)' reduces to 'f', but 'inline' has a BuiltInRule +-- that tries to inline 'f' (if it has an unfolding) unconditionally +-- The 'NOINLINE' pragma arranges that inline only gets inlined (and +-- hence eliminated) late in compilation, after the rule has had +-- a god chance to fire. +inline :: a -> a +{-# NOINLINE[0] inline #-} +inline x = x + +-- Assertion function. This simply ignores its boolean argument. +-- The compiler may rewrite it to @('assertError' line)@. + +-- | If the first argument evaluates to 'True', then the result is the +-- second argument. Otherwise an 'AssertionFailed' exception is raised, +-- containing a 'String' with the source file and line number of the +-- call to 'assert'. +-- +-- Assertions can normally be turned on or off with a compiler flag +-- (for GHC, assertions are normally on unless optimisation is turned on +-- with @-O@ or the @-fignore-asserts@ +-- option is given). When assertions are turned off, the first +-- argument to 'assert' is ignored, and the second argument is +-- returned as the result. --- Assertion function. This simply ignores its boolean argument. --- The compiler may rewrite it to (assertError line) -- SLPJ: in 5.04 etc 'assert' is in GHC.Prim, -- but from Template Haskell onwards it's simply -- defined here in Base.lhs assert :: Bool -> a -> a assert pred r = r - --- constant function + +breakpoint :: a -> a +breakpoint r = r + +breakpointCond :: Bool -> a -> a +breakpointCond _ r = r + +data Unknown +data Unknown1 a +data Unknown2 a b +data Unknown3 a b c +data Unknown4 a b c d + +data Opaque = forall a. O a + +-- | Constant function. const :: a -> b -> a const x _ = x --- function composition +-- | Function composition. {-# INLINE (.) #-} (.) :: (b -> c) -> (a -> b) -> a -> c (.) f g x = f (g x) --- flip f takes its (first) two arguments in the reverse order of f. +-- | @'flip' f@ takes its (first) two arguments in the reverse order of @f@. flip :: (a -> b -> c) -> b -> a -> c flip f x y = f y x --- right-associating infix application operator (useful in continuation- --- passing style) +-- | Application operator. This operator is redundant, since ordinary +-- application @(f x)@ means the same as @(f '$' x)@. However, '$' has +-- low, right-associative binding precedence, so it sometimes allows +-- parentheses to be omitted; for example: +-- +-- > f $ g $ h x = f (g (h x)) +-- +-- It is also useful in higher-order situations, such as @'map' ('$' 0) xs@, +-- or @'Data.List.zipWith' ('$') fs xs@. {-# INLINE ($) #-} ($) :: (a -> b) -> a -> b f $ x = f x --- until p f yields the result of applying f until p holds. +-- | @'until' p f@ yields the result of applying @f@ until @p@ holds. until :: (a -> Bool) -> (a -> a) -> a -> a until p f x | p x = x | otherwise = until p f (f x) --- asTypeOf is a type-restricted version of const. It is usually used --- as an infix operator, and its typing forces its first argument +-- | 'asTypeOf' is a type-restricted version of 'const'. It is usually +-- used as an infix operator, and its typing forces its first argument -- (which is usually overloaded) to have the same type as the second. asTypeOf :: a -> a -> a asTypeOf = const @@ -687,25 +778,6 @@ asTypeOf = const %********************************************************* %* * -\subsection{CCallable instances} -%* * -%********************************************************* - -Defined here to avoid orphans - -\begin{code} -instance CCallable Char -instance CReturnable Char - -instance CCallable Int -instance CReturnable Int - -instance CReturnable () -- Why, exactly? -\end{code} - - -%********************************************************* -%* * \subsection{Generics} %* * %********************************************************* @@ -869,22 +941,33 @@ gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool -- Note that these wrappers still produce undefined results when the -- second argument (the shift amount) is negative. -shiftL#, shiftRL# :: Word# -> Int# -> Word# - +-- | Shift the argument left by the specified number of bits +-- (which must be non-negative). +shiftL# :: Word# -> Int# -> Word# a `shiftL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0# | otherwise = a `uncheckedShiftL#` b +-- | Shift the argument right by the specified number of bits +-- (which must be non-negative). +shiftRL# :: Word# -> Int# -> Word# a `shiftRL#` b | b >=# WORD_SIZE_IN_BITS# = int2Word# 0# | otherwise = a `uncheckedShiftRL#` b -iShiftL#, iShiftRA#, iShiftRL# :: Int# -> Int# -> Int# - +-- | Shift the argument left by the specified number of bits +-- (which must be non-negative). +iShiftL# :: Int# -> Int# -> Int# a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0# | otherwise = a `uncheckedIShiftL#` b +-- | Shift the argument right (signed) by the specified number of bits +-- (which must be non-negative). +iShiftRA# :: Int# -> Int# -> Int# a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0# | otherwise = a `uncheckedIShiftRA#` b +-- | Shift the argument right (unsigned) by the specified number of bits +-- (which must be non-negative). +iShiftRL# :: Int# -> Int# -> Int# a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0# | otherwise = a `uncheckedIShiftRL#` b @@ -937,6 +1020,9 @@ unpackFoldrCString# :: Addr# -> (Char -> a -> a) -> a -> a {-# NOINLINE [0] unpackFoldrCString# #-} -- Don't inline till right at the end; -- usually the unpack-list rule turns it into unpackCStringList +-- It also has a BuiltInRule in PrelRules.lhs: +-- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n) +-- = unpackFoldrCString# "foobaz" c n unpackFoldrCString# addr f z = unpack 0# where @@ -991,3 +1077,12 @@ unpackNBytes# addr len# = unpack [] (len# -# 1#) #-} \end{code} + +#ifdef __HADDOCK__ +\begin{code} +-- | A special argument for the 'Control.Monad.ST.ST' type constructor, +-- indexing a state embedded in the 'Prelude.IO' monad by +-- 'Control.Monad.ST.stToIO'. +data RealWorld +\end{code} +#endif