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%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
%
\section[UniqSupply]{The @UniqueSupply@ data type and a (monadic) supply thereof}
\begin{code}
#include "HsVersions.h"
module UniqSupply (
UniqSupply, -- Abstractly
getUnique, getUniques, -- basic ops
SYN_IE(UniqSM), -- type: unique supply monad
initUs, thenUs, returnUs,
mapUs, mapAndUnzipUs, mapAndUnzip3Us,
thenMaybeUs, mapAccumLUs,
mkSplitUniqSupply,
splitUniqSupply
) where
IMP_Ubiq(){-uitous-}
import Unique
import Util
import PreludeGlaST
#if __GLASGOW_HASKELL__ >= 200
# define WHASH GHCbase.W#
#else
# define WHASH W#
#endif
w2i x = word2Int# x
i2w x = int2Word# x
i2w_s x = (x :: Int#)
\end{code}
%************************************************************************
%* *
\subsection{Splittable Unique supply: @UniqSupply@}
%* *
%************************************************************************
%************************************************************************
%* *
\subsubsection[UniqSupply-type]{@UniqSupply@ type and operations}
%* *
%************************************************************************
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)
getUnique :: UniqSupply -> Unique
getUniques :: Int -> UniqSupply -> [Unique]
\end{code}
\begin{code}
mkSplitUniqSupply (C# c#)
= let
mask# = (i2w (ord# c#)) `shiftL#` (i2w_s 24#)
-- here comes THE MAGIC:
mk_supply#
= unsafeInterleavePrimIO {-unsafe_interleave-} (
mk_unique `thenPrimIO` \ uniq ->
mk_supply# `thenPrimIO` \ s1 ->
mk_supply# `thenPrimIO` \ s2 ->
returnPrimIO (MkSplitUniqSupply uniq s1 s2)
)
where
{-
-- inlined copy of unsafeInterleavePrimIO;
-- this is the single-most-hammered bit of code
-- in the compiler....
-- Too bad it's not 1.3-portable...
unsafe_interleave m s
= let
(r, new_s) = m s
in
(r, s)
-}
mk_unique = _ccall_ genSymZh `thenPrimIO` \ (WHASH u#) ->
returnPrimIO (I# (w2i (mask# `or#` u#)))
in
#if __GLASGOW_HASKELL__ >= 200
primIOToIO mk_supply#
#else
mk_supply# `thenPrimIO` \ s ->
return s
#endif
splitUniqSupply (MkSplitUniqSupply _ s1 s2) = (s1, s2)
\end{code}
\begin{code}
getUnique (MkSplitUniqSupply (I# n) _ _) = mkUniqueGrimily n
getUniques (I# i) supply = i `get_from` supply
where
get_from 0# _ = []
get_from n (MkSplitUniqSupply (I# u) _ s2)
= mkUniqueGrimily u : get_from (n `minusInt#` 1#) s2
\end{code}
%************************************************************************
%* *
\subsubsection[UniqSupply-monad]{@UniqSupply@ monad: @UniqSM@}
%* *
%************************************************************************
\begin{code}
type UniqSM result = UniqSupply -> result
-- the initUs function also returns the final UniqSupply
initUs :: UniqSupply -> UniqSM a -> (UniqSupply, a)
initUs init_us m
= case (splitUniqSupply init_us) of { (s1, s2) ->
(s2, m s1) }
{-# INLINE thenUs #-}
{-# INLINE returnUs #-}
{-# INLINE splitUniqSupply #-}
\end{code}
@thenUs@ is where we split the @UniqSupply@.
\begin{code}
thenUs :: UniqSM a -> (a -> UniqSM b) -> UniqSM b
thenUs expr cont us
= case (splitUniqSupply us) of { (s1, s2) ->
case (expr s1) of { result ->
cont result s2 }}
\end{code}
\begin{code}
returnUs :: a -> UniqSM a
returnUs result us = result
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)
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}
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