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
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)
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
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
#include "MachDeps.h"
+-- #hide
module GHC.Base
(
module GHC.Base,
> 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
> 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
+ -- | 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
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,
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
"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
otherwise = True
\end{code}
-
%*********************************************************
%* *
\subsection{The @()@ type}
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 <http://www.unicode.org/> 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).
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}
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
+
--- | Assertion function. This simply ignores its boolean argument.
+-- | 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.
+
-- 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
-
+
+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
-- 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
{-# 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
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