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%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[UniqSupply]{The @UniqueSupply@ data type and a (monadic) supply thereof}
\begin{code}
module UniqSupply (
UniqSupply, -- Abstractly
uniqFromSupply, uniqsFromSupply, -- basic ops
UniqSM, -- type: unique supply monad
initUs, initUs_, thenUs, thenUs_, returnUs, fixUs, getUs, withUs,
getUniqueUs, getUniquesUs,
mapUs, mapAndUnzipUs, mapAndUnzip3Us,
thenMaybeUs, mapAccumLUs,
lazyThenUs, lazyMapUs,
mkSplitUniqSupply,
splitUniqSupply
) where
#include "HsVersions.h"
import Unique
import GLAEXTS
import UNSAFE_IO ( unsafeInterleaveIO )
w2i x = word2Int# x
i2w x = int2Word# x
i2w_s x = (x :: Int#)
\end{code}
%************************************************************************
%* *
\subsection{Splittable Unique supply: @UniqSupply@}
%* *
%************************************************************************
A value of type @UniqSupply@ is unique, and it can
supply {\em one} distinct @Unique@. Also, from the supply, one can
also manufacture an arbitrary number of further @UniqueSupplies@,
which will be distinct from the first and from all others.
\begin{code}
data UniqSupply
= MkSplitUniqSupply Int -- make the Unique with this
UniqSupply UniqSupply
-- when split => these two supplies
\end{code}
\begin{code}
mkSplitUniqSupply :: Char -> IO UniqSupply
splitUniqSupply :: UniqSupply -> (UniqSupply, UniqSupply)
uniqFromSupply :: UniqSupply -> Unique
uniqsFromSupply :: UniqSupply -> [Unique] -- Infinite
\end{code}
\begin{code}
mkSplitUniqSupply (C# c#)
= let
#if __GLASGOW_HASKELL__ >= 503
mask# = (i2w (ord# c#)) `uncheckedShiftL#` (i2w_s 24#)
#else
mask# = (i2w (ord# c#)) `shiftL#` (i2w_s 24#)
#endif
-- here comes THE MAGIC:
-- This is one of the most hammered bits in the whole compiler
mk_supply#
= unsafeInterleaveIO (
mk_unique >>= \ uniq ->
mk_supply# >>= \ s1 ->
mk_supply# >>= \ s2 ->
return (MkSplitUniqSupply uniq s1 s2)
)
mk_unique = genSymZh >>= \ (W# u#) ->
return (I# (w2i (mask# `or#` u#)))
in
mk_supply#
foreign import ccall unsafe "genSymZh" genSymZh :: IO Word
splitUniqSupply (MkSplitUniqSupply _ s1 s2) = (s1, s2)
\end{code}
\begin{code}
uniqFromSupply (MkSplitUniqSupply n _ _) = mkUniqueGrimily n
uniqsFromSupply (MkSplitUniqSupply n _ s2) = mkUniqueGrimily n : uniqsFromSupply s2
\end{code}
%************************************************************************
%* *
\subsubsection[UniqSupply-monad]{@UniqSupply@ monad: @UniqSM@}
%* *
%************************************************************************
\begin{code}
type UniqSM result = UniqSupply -> (result, UniqSupply)
-- the initUs function also returns the final UniqSupply; initUs_ drops it
initUs :: UniqSupply -> UniqSM a -> (a,UniqSupply)
initUs init_us m = case m init_us of { (r,us) -> (r,us) }
initUs_ :: UniqSupply -> UniqSM a -> a
initUs_ init_us m = case m init_us of { (r,us) -> r }
{-# INLINE thenUs #-}
{-# INLINE lazyThenUs #-}
{-# INLINE returnUs #-}
{-# INLINE splitUniqSupply #-}
\end{code}
@thenUs@ is where we split the @UniqSupply@.
\begin{code}
fixUs :: (a -> UniqSM a) -> UniqSM a
fixUs m us
= (r,us') where (r,us') = m r us
thenUs :: UniqSM a -> (a -> UniqSM b) -> UniqSM b
thenUs expr cont us
= case (expr us) of { (result, us') -> cont result us' }
lazyThenUs :: UniqSM a -> (a -> UniqSM b) -> UniqSM b
lazyThenUs expr cont us
= let (result, us') = expr us in cont result us'
thenUs_ :: UniqSM a -> UniqSM b -> UniqSM b
thenUs_ expr cont us
= case (expr us) of { (_, us') -> cont us' }
returnUs :: a -> UniqSM a
returnUs result us = (result, us)
withUs :: (UniqSupply -> (a, UniqSupply)) -> UniqSM a
withUs f us = f us -- Ha ha!
getUs :: UniqSM UniqSupply
getUs us = splitUniqSupply us
getUniqueUs :: UniqSM Unique
getUniqueUs us = case splitUniqSupply us of
(us1,us2) -> (uniqFromSupply us1, us2)
getUniquesUs :: UniqSM [Unique]
getUniquesUs us = case splitUniqSupply us of
(us1,us2) -> (uniqsFromSupply us1, us2)
\end{code}
\begin{code}
mapUs :: (a -> UniqSM b) -> [a] -> UniqSM [b]
mapUs f [] = returnUs []
mapUs f (x:xs)
= f x `thenUs` \ r ->
mapUs f xs `thenUs` \ rs ->
returnUs (r:rs)
lazyMapUs :: (a -> UniqSM b) -> [a] -> UniqSM [b]
lazyMapUs f [] = returnUs []
lazyMapUs f (x:xs)
= f x `lazyThenUs` \ r ->
lazyMapUs f xs `lazyThenUs` \ rs ->
returnUs (r:rs)
mapAndUnzipUs :: (a -> UniqSM (b,c)) -> [a] -> UniqSM ([b],[c])
mapAndUnzip3Us :: (a -> UniqSM (b,c,d)) -> [a] -> UniqSM ([b],[c],[d])
mapAndUnzipUs f [] = returnUs ([],[])
mapAndUnzipUs f (x:xs)
= f x `thenUs` \ (r1, r2) ->
mapAndUnzipUs f xs `thenUs` \ (rs1, rs2) ->
returnUs (r1:rs1, r2:rs2)
mapAndUnzip3Us f [] = returnUs ([],[],[])
mapAndUnzip3Us f (x:xs)
= f x `thenUs` \ (r1, r2, r3) ->
mapAndUnzip3Us f xs `thenUs` \ (rs1, rs2, rs3) ->
returnUs (r1:rs1, r2:rs2, r3:rs3)
thenMaybeUs :: UniqSM (Maybe a) -> (a -> UniqSM (Maybe b)) -> UniqSM (Maybe b)
thenMaybeUs m k
= m `thenUs` \ result ->
case result of
Nothing -> returnUs Nothing
Just x -> k x
mapAccumLUs :: (acc -> x -> UniqSM (acc, y))
-> acc
-> [x]
-> UniqSM (acc, [y])
mapAccumLUs f b [] = returnUs (b, [])
mapAccumLUs f b (x:xs)
= f b x `thenUs` \ (b__2, x__2) ->
mapAccumLUs f b__2 xs `thenUs` \ (b__3, xs__2) ->
returnUs (b__3, x__2:xs__2)
\end{code}
|
