module GHC.Base
(
module GHC.Base,
- module GHC.Prim, -- Re-export GHC.Prim and GHC.Err, to avoid lots
+ module GHC.Prim, -- Re-export GHC.Prim and GHC.Err, to avoid lots
module GHC.Err -- of people having to import it explicitly
)
where
%*********************************************************
\begin{code}
+{- | The 'Functor' class is used for types that can be mapped over.
+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.
+-}
+
class Functor f where
fmap :: (a -> b) -> f a -> f b
+{- | The 'Monad' class defines the basic operations over a /monad/.
+Instances of 'Monad' should satisfy the following laws:
+
+> return a >>= k == k a
+> m >>= return == m
+> m >>= (\x -> k x >>= h) == (m >>= k) >>= h
+
+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.
+-}
+
class Monad m where
(>>=) :: m a -> (a -> m b) -> m b
(>>) :: m a -> m b -> m b
----------------------------------------------
\begin{code}
+-- | 'foldr', applied to a binary operator, a starting value (typically
+-- the right-identity of the operator), and a list, reduces the list
+-- using the binary operator, from right to left:
+--
+-- > foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
+
foldr :: (a -> b -> b) -> b -> [a] -> b
-- foldr _ z [] = z
-- foldr f z (x:xs) = f x (foldr f z xs)
----------------------------------------------
\begin{code}
+-- | 'map' @f xs@ is the list obtained by applying @f@ to each element
+-- of @xs@, i.e.,
+--
+-- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
+-- > map f [x1, x2, ...] == [f x1, f x2, ...]
+
map :: (a -> b) -> [a] -> [b]
map _ [] = []
map f (x:xs) = f x : map f xs
-- append
----------------------------------------------
\begin{code}
+-- | Append two lists, i.e.,
+--
+-- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
+-- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
+--
+-- If the first list is not finite, the result is the first list.
+
(++) :: [a] -> [a] -> [a]
(++) [] ys = ys
(++) (x:xs) ys = x : xs ++ ys
\begin{code}
-- |The 'Bool' type is an enumeration. It is defined with 'False'
--- first so that the corresponding 'Enum' instance will give @'fromEnum'
--- False@ the value zero, and @'fromEnum' True@ the value 1.
+-- first so that the corresponding 'Prelude.Enum' instance will give
+-- 'Prelude.fromEnum' 'False' the value zero, and
+-- 'Prelude.fromEnum' 'True' the value 1.
data Bool = False | True deriving (Eq, Ord)
-- Read in GHC.Read, Show in GHC.Show
not True = False
not False = True
--- |'otherwise' is defined as the value 'True'; it helps to make
+-- |'otherwise' is defined as the value 'True'. It helps to make
-- guards more readable. eg.
--
--- > f x | x \< 0 = ...
+-- > f x | x < 0 = ...
-- > | otherwise = ...
otherwise :: Bool
otherwise = True
type String = [Char]
{-| The character type 'Char' is an enumeration whose values represent
-Unicode characters. A character literal in Haskell has type 'Char'.
-
-To convert a 'Char' to or from an 'Int', use 'Prelude.toEnum' and
-'Prelude.fromEnum' from the 'Enum' class respectively (equivalently
-'ord' and 'chr' also do the trick).
+Unicode (or equivalently ISO 10646) characters.
+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).
+A character literal in Haskell has type 'Char'.
+
+To convert a 'Char' to or from the corresponding 'Int' value defined
+by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
+'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
-}
data Char = C# Char#
"x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
#-}
+-- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.
chr :: Int -> Char
chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
| otherwise = error "Prelude.chr: bad argument"
unsafeChr :: Int -> Char
unsafeChr (I# i#) = C# (chr# i#)
+-- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.
ord :: Char -> Int
ord (C# c#) = I# (ord# c#)
\end{code}
lazy :: a -> a
lazy x = x
+-- 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
const :: a -> b -> a
const x _ = x
#endif
\end{code}
+%*********************************************************
+%* *
+\subsection{@getTag@}
+%* *
+%*********************************************************
+
+Returns the 'tag' of a constructor application; this function is used
+by the deriving code for Eq, Ord and Enum.
+
+The primitive dataToTag# requires an evaluated constructor application
+as its argument, so we provide getTag as a wrapper that performs the
+evaluation before calling dataToTag#. We could have dataToTag#
+evaluate its argument, but we prefer to do it this way because (a)
+dataToTag# can be an inline primop if it doesn't need to do any
+evaluation, and (b) we want to expose the evaluation to the
+simplifier, because it might be possible to eliminate the evaluation
+in the case when the argument is already known to be evaluated.
+
+\begin{code}
+{-# INLINE getTag #-}
+getTag :: a -> Int#
+getTag x = x `seq` dataToTag# x
+\end{code}
%*********************************************************
%* *
\begin{code}
divInt# :: Int# -> Int# -> Int#
x# `divInt#` y#
- -- careful NOT to overflow if we do any additional arithmetic
+ -- Be careful NOT to overflow if we do any additional arithmetic
-- on the arguments... the following previous version of this
-- code has problems with overflow:
-- | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
-- | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
- | (x# ># 0#) && (y# <# 0#) = (x# -# 1#) `quotInt#` y# -# 1#
- | (x# <# 0#) && (y# ># 0#) = (x# +# 1#) `quotInt#` y# -# 1#
+ | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
+ | (x# <# 0#) && (y# ># 0#) = ((x# +# 1#) `quotInt#` y#) -# 1#
| otherwise = x# `quotInt#` y#
modInt# :: Int# -> Int# -> Int#
| ch `eqChar#` '\0'# = []
| ch `leChar#` '\x7F'# = C# ch : unpack (nh +# 1#)
| ch `leChar#` '\xDF'# =
- C# (chr# ((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6# +#
- (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
+ C# (chr# (((ord# ch -# 0xC0#) `uncheckedIShiftL#` 6#) +#
+ (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#))) :
unpack (nh +# 2#)
| ch `leChar#` '\xEF'# =
- C# (chr# ((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12# +#
- (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6# +#
- (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
+ C# (chr# (((ord# ch -# 0xE0#) `uncheckedIShiftL#` 12#) +#
+ ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
+ (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#))) :
unpack (nh +# 3#)
| otherwise =
- C# (chr# ((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18# +#
- (ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12# +#
- (ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6# +#
- (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
+ C# (chr# (((ord# ch -# 0xF0#) `uncheckedIShiftL#` 18#) +#
+ ((ord# (indexCharOffAddr# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
+ ((ord# (indexCharOffAddr# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#` 6#) +#
+ (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
unpack (nh +# 4#)
where
ch = indexCharOffAddr# addr nh
#-}
\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