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add length axioms

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2021-07-13 14:22:58 +02:00
parent a49a5b3a0b
commit 0752b1385c
4 changed files with 43 additions and 10 deletions
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26
src/ast/rewriter/seq_axioms.cpp
View file

@ -786,15 +786,37 @@ namespace seq {
unsigned sz = bv.get_bv_size(b);
expr_ref_vector es(m);
expr_ref bb(b, m), ten(bv.mk_numeral(10, sz), m);
for (unsigned i = 0; i < k; ++i) {
pow = 1;
for (unsigned i = 0; i <= k; ++i) {
if (pow > 1)
bb = bv.mk_bv_udiv(b, bv.mk_numeral(pow, bv_sort));
es.push_back(seq.str.mk_unit(m_sk.mk_ubv2ch(bv.mk_bv_urem(bb, ten))));
bb = bv.mk_bv_udiv(bb, ten);
pow *= 10;
}
es.reverse();
eq = m.mk_eq(seq.str.mk_ubv2s(b), seq.str.mk_concat(es, seq.str.mk_string_sort()));
add_clause(~ge10k, ge10k1, eq);
}
/*
* len(ubv2s(b)) = k => 10^k-1 <= b < 10^{k} k > 1
* len(ubv2s(b)) = 1 => b < 10^{1} k = 1
*/
void axioms::ubv2s_len_axiom(expr* b, unsigned k) {
expr_ref ge10k(m), ge10k1(m), eq(m);
bv_util bv(m);
sort* bv_sort = b->get_sort();
rational pow(1);
for (unsigned i = 1; i < k; ++i)
pow *= 10;
ge10k = bv.mk_ule(bv.mk_numeral(pow, bv_sort), b);
ge10k1 = bv.mk_ule(bv.mk_numeral(pow * 10, bv_sort), b);
eq = m.mk_eq(seq.str.mk_length(seq.str.mk_ubv2s(b)), a.mk_int(k));
add_clause(~eq, ~ge10k1);
if (k > 1)
add_clause(~eq, ge10k);
}
void axioms::ubv2ch_axiom(sort* bv_sort) {
bv_util bv(m);
expr_ref eq(m);

1
src/ast/rewriter/seq_axioms.h
View file

@ -95,6 +95,7 @@ namespace seq {
void stoi_axiom(expr* e, unsigned k);
void itos_axiom(expr* s, unsigned k);
void ubv2s_axiom(expr* b, unsigned k);
void ubv2s_len_axiom(expr* b, unsigned k);
void ubv2ch_axiom(sort* bv_sort);
void lt_axiom(expr* n);
void le_axiom(expr* n);

1
src/smt/seq_axioms.h
View file

@ -80,6 +80,7 @@ namespace smt {
void add_stoi_axiom(expr* e, unsigned k) { m_ax.stoi_axiom(e, k); }
void add_itos_axiom(expr* s, unsigned k) { m_ax.itos_axiom(s, k); }
void add_ubv2s_axiom(expr* b, unsigned k) { m_ax.ubv2s_axiom(b, k); }
void add_ubv2s_len_axiom(expr* b, unsigned k) { m_ax.ubv2s_len_axiom(b, k); }
void add_ubv2ch_axioms(sort* s) { m_ax.ubv2ch_axiom(s); }
void add_lt_axiom(expr* n) { m_ax.lt_axiom(n); }
void add_le_axiom(expr* n) { m_ax.le_axiom(n); }

25
src/smt/theory_seq.cpp
View file

@ -1532,8 +1532,19 @@ bool theory_seq::add_length_to_eqc(expr* e) {
}
void theory_seq::add_ubv_string(expr* e) {
bool has_sort = false;
expr* b = nullptr;
VERIFY(m_util.str.is_ubv2s(e, b));
for (auto* e2 : m_ubv_string) {
expr* b2 = nullptr;
VERIFY(m_util.str.is_ubv2s(e2, b2));
has_sort |= b2->get_sort() == b->get_sort();
}
if (!has_sort)
m_ax.add_ubv2ch_axioms(b->get_sort());
m_ubv_string.push_back(e);
m_trail_stack.push(push_back_vector<expr_ref_vector>(m_ubv_string));
add_length_to_eqc(e);
}
bool theory_seq::check_ubv_string() {
@ -1554,6 +1565,11 @@ bool theory_seq::check_ubv_string(expr* e) {
expr* b = nullptr;
bv_util bv(m);
VERIFY(m_util.str.is_ubv2s(e, b));
rational len;
if (get_length(e, len) && len.is_unsigned())
m_ax.add_ubv2s_len_axiom(b, len.get_unsigned());
unsigned sz = bv.get_bv_size(b);
rational value(0);
bool all_bits_assigned = true;
@ -1579,14 +1595,7 @@ bool theory_seq::check_ubv_string(expr* e) {
k++;
value = div(value, rational(10));
}
bool has_sort = false;
for (auto* e2 : m_has_ubv_axiom) {
expr* b2 = nullptr;
VERIFY(m_util.str.is_ubv2s(e2, b2));
has_sort |= b2->get_sort() == b->get_sort();
}
if (!has_sort)
m_ax.add_ubv2ch_axioms(b->get_sort());
m_has_ubv_axiom.insert(e);
m_trail_stack.push(insert_obj_trail<expr>(m_has_ubv_axiom, e));
m_ax.add_ubv2s_axiom(b, k);