UniqSupply.lhs 4.74 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
%
% (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

	UniqSM(..),		-- type: unique supply monad
	initUs, thenUs, returnUs,
17
	mapUs, mapAndUnzipUs, mapAndUnzip3Us,
18
	thenMaybeUs, mapAccumLUs,
19
20

	mkSplitUniqSupply,
21
	splitUniqSupply
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
  ) where

import Ubiq{-uitous-}

import Unique
import Util

import PreludeGlaST

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}
62
mkSplitUniqSupply :: Char -> IO UniqSupply
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95

splitUniqSupply :: UniqSupply -> (UniqSupply, UniqSupply)
getUnique :: UniqSupply -> Unique
getUniques :: Int -> UniqSupply -> [Unique]
\end{code}

\begin{code}
mkSplitUniqSupply (MkChar c#)
  = let
	mask# = (i2w (ord# c#)) `shiftL#` (i2w_s 24#)

	-- here comes THE MAGIC:

	mk_supply#
	  = 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....
	    unsafe_interleave m s
	      = let
		    (r, new_s) = m s
		in
		(r, s)

	mk_unique = _ccall_ genSymZh		`thenPrimIO` \ (W# u#) ->
		    returnPrimIO (MkInt (w2i (mask# `or#` u#)))
    in
96
97
    mk_supply#	`thenPrimIO` \ s ->
    return s
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156

splitUniqSupply (MkSplitUniqSupply _ s1 s2) = (s1, s2)
\end{code}

\begin{code}
getUnique (MkSplitUniqSupply (MkInt n) _ _) = mkUniqueGrimily n

getUniques i@(MkInt i#) supply = i# `get_from` supply
  where
    get_from 0# _ = []
    get_from n# (MkSplitUniqSupply (MkInt 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])
157
mapAndUnzip3Us :: (a -> UniqSM (b,c,d)) -> [a] -> UniqSM ([b],[c],[d])
158
159
160
161
162
163

mapAndUnzipUs f [] = returnUs ([],[])
mapAndUnzipUs f (x:xs)
  = f x		    	`thenUs` \ (r1,  r2)  ->
    mapAndUnzipUs f xs	`thenUs` \ (rs1, rs2) ->
    returnUs (r1:rs1, r2:rs2)
164
165
166
167
168
169

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)
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187

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)
188
\end{code}