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
|
/********************* */
/*! \file node_traversal.cpp
** \verbatim
** Top contributors (to current version):
** Alex Ozdemir, Andres Noetzli
** This file is part of the CVC4 project.
** Copyright (c) 2009-2020 by the authors listed in the file AUTHORS
** in the top-level source directory) and their institutional affiliations.
** All rights reserved. See the file COPYING in the top-level source
** directory for licensing information.\endverbatim
**
** \brief Iterators for traversing nodes.
**/
#include "node_traversal.h"
namespace CVC4 {
NodeDfsIterator::NodeDfsIterator(TNode n,
VisitOrder order,
std::function<bool(TNode)> skipIf)
: d_stack{n},
d_visited(),
d_order(order),
d_current(TNode()),
d_skipIf(skipIf)
{
}
NodeDfsIterator::NodeDfsIterator(VisitOrder order)
: d_stack(),
d_visited(),
d_order(order),
d_current(TNode()),
d_skipIf([](TNode) { return false; })
{
}
NodeDfsIterator& NodeDfsIterator::operator++()
{
// If we were just constructed, advance to first visit, **before**
// advancing past it to the next visit (below).
initializeIfUninitialized();
// Advance to the next visit
advanceToNextVisit();
return *this;
}
NodeDfsIterator NodeDfsIterator::operator++(int)
{
NodeDfsIterator copyOfOld(*this);
++*this;
return copyOfOld;
}
TNode& NodeDfsIterator::operator*()
{
// If we were just constructed, advance to first visit
initializeIfUninitialized();
Assert(!d_current.isNull());
return d_current;
}
bool NodeDfsIterator::operator==(const NodeDfsIterator& other) const
{
// The stack and current node uniquely represent traversal state. We need not
// use the scheduled node set.
//
// Users should not compare iterators for traversals of different nodes, or
// traversals with different skipIfs.
Assert(d_order == other.d_order);
return d_stack == other.d_stack && d_current == other.d_current;
}
bool NodeDfsIterator::operator!=(const NodeDfsIterator& other) const
{
return !(*this == other);
}
void NodeDfsIterator::advanceToNextVisit()
{
// While a node is enqueued and we're not at the right visit type
while (!d_stack.empty())
{
TNode back = d_stack.back();
auto visitEntry = d_visited.find(back);
if (visitEntry == d_visited.end())
{
// if we haven't pre-visited this node, pre-visit it
if (d_skipIf(back))
{
// actually, skip it if the skip predicate says so...
d_stack.pop_back();
continue;
}
d_visited[back] = false;
d_current = back;
// Use integer underflow to reverse-iterate
for (size_t n = back.getNumChildren(), i = n - 1; i < n; --i)
{
d_stack.push_back(back[i]);
}
if (d_order == VisitOrder::PREORDER)
{
return;
}
}
else if (d_order == VisitOrder::PREORDER || visitEntry->second)
{
// if we're previsiting or we've already post-visited this node: skip it
d_stack.pop_back();
}
else
{
// otherwise, this is a post-visit
visitEntry->second = true;
d_current = back;
d_stack.pop_back();
return;
}
}
// We're at the end of the traversal: nullify the current node to agree
// with the "end" iterator.
d_current = TNode();
}
void NodeDfsIterator::initializeIfUninitialized()
{
if (d_current.isNull())
{
advanceToNextVisit();
}
}
NodeDfsIterable::NodeDfsIterable(TNode n,
VisitOrder order,
std::function<bool(TNode)> skipIf)
: d_node(n), d_order(order), d_skipIf(skipIf)
{
}
NodeDfsIterator NodeDfsIterable::begin() const
{
return NodeDfsIterator(d_node, d_order, d_skipIf);
}
NodeDfsIterator NodeDfsIterable::end() const
{
return NodeDfsIterator(d_order);
}
} // namespace CVC4
|
