%*********************************************************
\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}
-- |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}
-- 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
#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}
%*********************************************************
%* *
projects / ghc-base.git / blobdiff