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fix #4019

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2020-04-19 12:36:34 -07:00
parent 339a2568b2
commit fcc34a07b2
1 changed files with 16 additions and 12 deletions
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28
src/smt/seq_axioms.cpp
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@ -401,15 +401,19 @@ void seq_axioms::add_last_indexof_axiom(expr* i) {
} }
/* /*
let r = replace(a, s, t) let r = replace(u, s, t)
a = "" => s = "" or r = a
contains(a, s) or r = a - if s is empty, the result is to prepend t to u;
s = "" => r = t+a - if s does not occur in u then the result is u.
s = "" => r = t+u
u = "" => s = "" or r = u
~contains(u,s) => r = u
tightest_prefix(s, x) tightest_prefix(s, x)
(contains(a, s) -> r = xty & a = xsy) & contains(u, s) => r = xty & u = xsy
(!contains(a, s) -> r = a) ~contains(u, s) => r = u
*/ */
void seq_axioms::add_replace_axiom(expr* r) { void seq_axioms::add_replace_axiom(expr* r) {
@ -419,14 +423,14 @@ void seq_axioms::add_replace_axiom(expr* r) {
expr_ref y = m_sk.mk_indexof_right(u, s); expr_ref y = m_sk.mk_indexof_right(u, s);
expr_ref xty = mk_concat(x, t, y); expr_ref xty = mk_concat(x, t, y);
expr_ref xsy = mk_concat(x, s, y); expr_ref xsy = mk_concat(x, s, y);
literal a_emp = mk_eq_empty(u, true); literal u_emp = mk_eq_empty(u, true);
literal s_emp = mk_eq_empty(u, true); literal s_emp = mk_eq_empty(s, true);
literal cnt = mk_literal(seq.str.mk_contains(u, s)); literal cnt = mk_literal(seq.str.mk_contains(u, s));
add_axiom(~a_emp, s_emp, mk_seq_eq(r, u));
add_axiom(cnt, mk_seq_eq(r, u));
add_axiom(~s_emp, mk_seq_eq(r, mk_concat(t, u))); add_axiom(~s_emp, mk_seq_eq(r, mk_concat(t, u)));
add_axiom(~cnt, a_emp, s_emp, mk_seq_eq(u, xsy)); add_axiom(~u_emp, s_emp, mk_seq_eq(r, u));
add_axiom(~cnt, a_emp, s_emp, mk_seq_eq(r, xty)); add_axiom(cnt, mk_seq_eq(r, u));
add_axiom(~cnt, u_emp, s_emp, mk_seq_eq(u, xsy));
add_axiom(~cnt, u_emp, s_emp, mk_seq_eq(r, xty));
ctx().force_phase(cnt); ctx().force_phase(cnt);
tightest_prefix(s, x); tightest_prefix(s, x);
} }