1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
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
62
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
96
97
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
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
|
/********************* */
/*! \file theory_bool.cpp
** \verbatim
** Original author: mdeters
** Major contributors: none
** Minor contributors (to current version): none
** This file is part of the CVC4 prototype.
** Copyright (c) 2009, 2010 The Analysis of Computer Systems Group (ACSys)
** Courant Institute of Mathematical Sciences
** New York University
** See the file COPYING in the top-level source directory for licensing
** information.\endverbatim
**
** \brief The theory of booleans.
**
** The theory of booleans.
**/
#include "theory/theory.h"
#include "theory/booleans/theory_bool.h"
#include "theory/theory_engine.h"
namespace CVC4 {
namespace theory {
namespace booleans {
RewriteResponse TheoryBool::preRewrite(TNode n, bool topLevel) {
if(n.getKind() == kind::IFF) {
NodeManager* nodeManager = NodeManager::currentNM();
Node tt = nodeManager->mkConst(true);
Node ff = nodeManager->mkConst(false);
// rewrite simple cases of IFF
if(n[0] == tt) {
// IFF true x
return RewriteAgain(n[1]);
} else if(n[1] == tt) {
// IFF x true
return RewriteAgain(n[0]);
} else if(n[0] == ff) {
// IFF false x
return RewriteAgain(n[1].notNode());
} else if(n[1] == ff) {
// IFF x false
return RewriteAgain(n[0].notNode());
} else if(n[0] == n[1]) {
// IFF x x
return RewriteComplete(tt);
} else if(n[0].getKind() == kind::NOT && n[0][0] == n[1]) {
// IFF (NOT x) x
return RewriteComplete(ff);
} else if(n[1].getKind() == kind::NOT && n[1][0] == n[0]) {
// IFF x (NOT x)
return RewriteComplete(ff);
}
} else if(n.getKind() == kind::ITE) {
// non-Boolean-valued ITEs should have been removed in place of
// a variable
Assert(n.getType().isBoolean());
NodeManager* nodeManager = NodeManager::currentNM();
// rewrite simple cases of ITE
if(n[0] == nodeManager->mkConst(true)) {
// ITE true x y
return RewriteAgain(n[1]);
} else if(n[0] == nodeManager->mkConst(false)) {
// ITE false x y
return RewriteAgain(n[2]);
} else if(n[1] == n[2]) {
// ITE c x x
return RewriteAgain(n[1]);
}
}
return RewriteComplete(n);
}
RewriteResponse TheoryBool::postRewrite(TNode n, bool topLevel) {
if(n.getKind() == kind::IFF) {
NodeManager* nodeManager = NodeManager::currentNM();
Node tt = nodeManager->mkConst(true);
Node ff = nodeManager->mkConst(false);
// rewrite simple cases of IFF
if(n[0] == tt) {
// IFF true x
return RewriteComplete(n[1]);
} else if(n[1] == tt) {
// IFF x true
return RewriteComplete(n[0]);
} else if(n[0] == ff) {
// IFF false x
return RewriteAgain(n[1].notNode());
} else if(n[1] == ff) {
// IFF x false
return RewriteAgain(n[0].notNode());
} else if(n[0] == n[1]) {
// IFF x x
return RewriteComplete(tt);
} else if(n[0].getKind() == kind::NOT && n[0][0] == n[1]) {
// IFF (NOT x) x
return RewriteComplete(ff);
} else if(n[1].getKind() == kind::NOT && n[1][0] == n[0]) {
// IFF x (NOT x)
return RewriteComplete(ff);
}
if(n[1] < n[0]) {
// normalize (IFF x y) ==> (IFF y x), if y < x
return RewriteComplete(n[1].iffNode(n[0]));
}
} else if(n.getKind() == kind::ITE) {
// non-Boolean-valued ITEs should have been removed in place of
// a variable
Assert(n.getType().isBoolean());
NodeManager* nodeManager = NodeManager::currentNM();
// rewrite simple cases of ITE
if(n[0] == nodeManager->mkConst(true)) {
// ITE true x y
return RewriteComplete(n[1]);
} else if(n[0] == nodeManager->mkConst(false)) {
// ITE false x y
return RewriteComplete(n[2]);
} else if(n[1] == n[2]) {
// ITE c x x
return RewriteComplete(n[1]);
}
if(n[0].getKind() == kind::NOT) {
// rewrite (ITE (NOT c) x y) to (ITE c y x)
Node out = nodeManager->mkNode(kind::ITE, n[0][0], n[2], n[1]);
return RewriteComplete(out);
}
}
return RewriteComplete(n);
}
Node TheoryBool::getValue(TNode n, TheoryEngine* engine) {
NodeManager* nodeManager = NodeManager::currentNM();
switch(n.getKind()) {
case kind::VARIABLE:
// case for Boolean vars is implemented in TheoryEngine (since it
// appeals to the PropEngine to get the value)
Unreachable();
case kind::EQUAL: // 2 args
// should be handled by IFF
Unreachable();
case kind::NOT: // 1 arg
return nodeManager->mkConst(! engine->getValue(n[0]).getConst<bool>());
case kind::AND: { // 2+ args
for(TNode::iterator i = n.begin(),
iend = n.end();
i != iend;
++i) {
if(! engine->getValue(*i).getConst<bool>()) {
return nodeManager->mkConst(false);
}
}
return nodeManager->mkConst(true);
}
case kind::IFF: // 2 args
return nodeManager->mkConst( engine->getValue(n[0]).getConst<bool>() ==
engine->getValue(n[1]).getConst<bool>() );
case kind::IMPLIES: // 2 args
return nodeManager->mkConst( (! engine->getValue(n[0]).getConst<bool>()) ||
engine->getValue(n[1]).getConst<bool>() );
case kind::OR: { // 2+ args
for(TNode::iterator i = n.begin(),
iend = n.end();
i != iend;
++i) {
if(engine->getValue(*i).getConst<bool>()) {
return nodeManager->mkConst(true);
}
}
return nodeManager->mkConst(false);
}
case kind::XOR: // 2 args
return nodeManager->mkConst( engine->getValue(n[0]).getConst<bool>() !=
engine->getValue(n[1]).getConst<bool>() );
case kind::ITE: // 3 args
// all ITEs should be gone except (bool,bool,bool) ones
Assert( n[1].getType() == nodeManager->booleanType() &&
n[2].getType() == nodeManager->booleanType() );
return nodeManager->mkConst( engine->getValue(n[0]).getConst<bool>() ?
engine->getValue(n[1]).getConst<bool>() :
engine->getValue(n[2]).getConst<bool>() );
default:
Unhandled(n.getKind());
}
}
}/* CVC4::theory::booleans namespace */
}/* CVC4::theory namespace */
}/* CVC4 namespace */
|
