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
|
/*
* richard-atp-engine: A saturation-based automated theorem prover for first-order logic.
* Copyright (C) 2026 Richard Qin
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include "atp/infer/unification.h"
#include "atp/core/types.h"
#include "atp/infer/substitution.h"
namespace atp {
bool unify(const TermBank& bank, TermId t1, TermId t2, Substitution& subst,
const UnificationConfig& config) {
t1 = subst.resolve(t1, bank);
t2 = subst.resolve(t2, bank);
if (t1 == t2) {
return true;
}
if (bank.isVariable(t1)) {
if (config.enable_occurs_check && subst.occursIn(t1, t2, bank)) {
return false;
}
subst.bind(t1, t2);
return true;
}
if (bank.isVariable(t2)) {
if (config.enable_occurs_check && subst.occursIn(t2, t1, bank)) {
return false;
}
subst.bind(t2, t1);
return true;
}
const Term& term1 = bank.getTerm(t1);
const Term& term2 = bank.getTerm(t2);
if (term1.symbol_id != term2.symbol_id || term1.arity() != term2.arity()) {
return false;
}
for (size_t i = 0; i < term1.arity(); ++i) {
if (!unify(bank, term1.args[i], term2.args[i], subst, config)) {
return false;
}
}
return true;
}
TermId applySubstitution(const Substitution& subst, TermId term, TermBank& bank) {
term = subst.resolve(term, bank);
if (bank.isVariable(term)) {
return term;
}
// IMPORTANT: Copy args and symbol_id BEFORE recursing.
// Recursive calls may call bank.makeTerm() → realloc terms_ → invalidate refs.
const Term& t = bank.getTerm(term);
SymbolId sym = t.symbol_id;
std::vector<TermId> old_args(t.args); // copy!
std::vector<TermId> new_args;
new_args.reserve(old_args.size());
for (TermId arg : old_args) {
new_args.push_back(applySubstitution(subst, arg, bank));
}
return bank.makeTerm(sym, new_args);
}
} // namespace atp
|
