merge GHC HEAD

[ghc-hetmet.git] / compiler / utils / State.hs

diff --git a/compiler/utils/State.hs b/compiler/utils/State.hs
index a0d21d6..0b6a285 100644 (file)
--- a/compiler/utils/State.hs
+++ b/compiler/utils/State.hs
@@ -1,63 +1,48 @@
-{-# OPTIONS -w #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
---     http://hackage.haskell.org/trac/ghc/wiki/CodingStyle#Warnings
--- for details
 
-module State where
+module State (module State, mapAccumLM {- XXX hack -}) where
 
-newtype State s a
-       = State
-       { runState' :: s -> (# a, s #) }
+import MonadUtils
+
+newtype State s a = State { runState' :: s -> (# a, s #) }
+
+instance Functor (State s) where
+    fmap f m  = State $ \s -> case runState' m s of
+                              (# r, s' #) -> (# f r, s' #)
+
+instance Applicative (State s) where
+   pure x   = State $ \s -> (# x, s #)
+   m <*> n  = State $ \s -> case runState' m s of
+                            (# f, s' #) -> case runState' n s' of
+                                           (# x, s'' #) -> (# f x, s'' #)
 
 instance Monad (State s) where
-    return x   = State $ \s -> (# x, s #)
-    m >>= n    = State $ \s ->
-                       case runState' m s of
-                         (# r, s' #)   -> runState' (n r) s'
+    return x = State $ \s -> (# x, s #)
+    m >>= n  = State $ \s -> case runState' m s of
+                             (# r, s' #) -> runState' (n r) s'
 
-get :: State s s
-get    = State $ \s -> (# s, s #)
+get :: State s s
+get = State $ \s -> (# s, s #)
 
 gets :: (s -> a) -> State s a
-gets f         = State $ \s -> (# f s, s #)
+gets f = State $ \s -> (# f s, s #)
 
-put ::         s -> State s ()
-put s' = State $ \s -> (# (), s' #)
+put :: s -> State s ()
+put s' = State $ \_ -> (# (), s' #)
 
 modify :: (s -> s) -> State s ()
 modify f = State $ \s -> (# (), f s #)
 
 
 evalState :: State s a -> s -> a
-evalState s i
-       = case runState' s i of
-               (# a, s' #)     -> a
+evalState s i = case runState' s i of
+                (# a, _ #) -> a
 
 
 execState :: State s a -> s -> s
-execState s i
-       = case runState' s i of
-               (# a, s' #)     -> s'
+execState s i = case runState' s i of
+                (# _, s' #) -> s'
 
 
 runState :: State s a -> s -> (a, s)
-runState s i
-       = case runState' s i of
-               (# a, s' #)     -> (a, s')
-
-
-mapAccumLM
-       :: Monad m
-       => (acc -> x -> m (acc, y))     -- ^ combining funcction
-       -> acc                          -- ^ initial state
-       -> [x]                          -- ^ inputs
-       -> m (acc, [y])                 -- ^ final state, outputs
-
-mapAccumLM _ s []      = return (s, [])
-mapAccumLM f s (x:xs)
- = do
-       (s1, x')        <- f s x
-       (s2, xs')       <- mapAccumLM f s1 xs
-       return          (s2, x' : xs')
+runState s i = case runState' s i of
+               (# a, s' #) -> (a, s')