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adding comparison #2360

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2019-06-28 21:14:58 -07:00
parent db274ebe01
commit 335543b374
9 changed files with 143 additions and 4 deletions
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61
src/smt/theory_seq.cpp
View file

@ -4941,6 +4941,7 @@ void theory_seq::add_extract_axiom(expr* e) {
TRACE("seq", tout << mk_pp(e, m) << "\n";);
expr* s = nullptr, *i = nullptr, *l = nullptr;
VERIFY(m_util.str.is_extract(e, s, i, l));
#if 0
if (is_tail(s, i, l)) {
add_tail_axiom(e, s);
return;
@ -4957,7 +4958,7 @@ void theory_seq::add_extract_axiom(expr* e) {
add_extract_suffix_axiom(e, s, i);
return;
}
#endif
expr_ref x(mk_skolem(m_pre, s, i), m);
expr_ref ls = mk_len(s);
expr_ref lx = mk_len(x);
@ -5450,6 +5451,22 @@ void theory_seq::assign_eh(bool_var v, bool is_true) {
m_ncs.push_back(nc(expr_ref(e, m), len_gt, dep));
}
}
else if (m_util.str.is_lt(e, e1, e2)) {
if (is_true) {
propagate_lt(lit, e1, e2);
}
else {
propagate_le(lit, e2, e1);
}
}
else if (m_util.str.is_le(e, e1, e2)) {
if (is_true) {
propagate_le(lit, e1, e2);
}
else {
propagate_lt(lit, e2, e1);
}
}
else if (is_accept(e)) {
if (is_true) {
propagate_accept(lit, e);
@ -5902,7 +5919,49 @@ void theory_seq::propagate_not_suffix(expr* e) {
add_axiom(lit, e1_gt_e2, ~mk_eq(c, d, false));
}
/**
lit == e1 < e2:
lit => e1 = empty or e1 = xcy
lit => e1 = empty or e2 = xdz
lit => e1 = empty or c < d
lit => e1 != empty or e2 != empty
*/
void theory_seq::propagate_lt(literal lit, expr* e1, expr* e2) {
sort* s = m.get_sort(e1);
sort* char_sort = nullptr;
VERIFY(m_util.is_seq(s, char_sort));
expr_ref x = mk_skolem(symbol("str.lt.x"), e1, e2);
expr_ref y = mk_skolem(symbol("str.lt.y"), e1, e2);
expr_ref z = mk_skolem(symbol("str.lt.z"), e1, e2);
expr_ref c = mk_skolem(symbol("str.lt.c"), e1, e2, nullptr, nullptr, char_sort);
expr_ref d = mk_skolem(symbol("str.lt.d"), e1, e2, nullptr, nullptr, char_sort);
expr_ref empty_string(m_util.str.mk_empty(s), m);
literal emp = mk_eq(e1, empty_string, false);
add_axiom(~lit, ~mk_eq(e1, e2, false));
add_axiom(~lit, emp, mk_eq(e1, mk_concat(x, m_util.str.mk_unit(c), y), false));
add_axiom(~lit, emp, mk_eq(e2, mk_concat(x, m_util.str.mk_unit(d), z), false));
add_axiom(~lit, emp, mk_literal(m_util.mk_lt(c, d)));
add_axiom(~lit, ~emp, ~mk_eq(e2, empty_string, false));
}
/**
lit => e1 <= e2
e1 < e2 or e1 = e2 or e2 < e1
!(e1 = e2) or !(e1 < e2)
!(e1 = e2) or !(e2 < e1)
!(e1 < e2) or !(e2 < e1)
lit => e1 < e2 or e1 = e2
*/
void theory_seq::propagate_le(literal lit, expr* e1, expr* e2) {
literal lt_e1e2 = mk_literal(m_util.mk_lt(e1, e2));
literal lt_e2e1 = mk_literal(m_util.mk_lt(e2, e1));
literal eq = mk_eq(e1, e2, false);
add_axiom(eq, lt_e1e2, lt_e2e1);
add_axiom(lit, eq, lt_e1e2);
add_axiom(~eq, ~lt_e1e2);
add_axiom(~eq, ~lt_e2e1);
add_axiom(~lt_e1e2, ~lt_e2e1);
}
bool theory_seq::canonizes(bool sign, expr* e) {
context& ctx = get_context();

2
src/smt/theory_seq.h
View file

@ -646,6 +646,8 @@ namespace smt {
void propagate_step(literal lit, expr* n);
void propagate_accept(literal lit, expr* e);
void new_eq_eh(dependency* dep, enode* n1, enode* n2);
void propagate_lt(literal lit, expr* e1, expr* e2);
void propagate_le(literal lit, expr* e1, expr* e2);
// diagnostics
std::ostream& display_equations(std::ostream& out) const;