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fix #4589

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2020-07-24 15:46:54 -07:00
parent 780346c7ca
commit e63992c8bd
3 changed files with 14 additions and 3 deletions
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6
src/smt/seq_axioms.cpp
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@ -252,10 +252,14 @@ void seq_axioms::add_extract_suffix_axiom(expr* e, expr* s, expr* i) {
s = "" or !contains(x*s1, s)
*/
void seq_axioms::tightest_prefix(expr* s, expr* x) {
literal s_eq_emp = mk_eq_empty(s);
if (seq.str.max_length(s) <= 1) {
add_axiom(s_eq_emp, ~mk_literal(seq.str.mk_contains(x, s)));
return;
}
expr_ref s1 = m_sk.mk_first(s);
expr_ref c = m_sk.mk_last(s);
expr_ref s1c = mk_concat(s1, seq.str.mk_unit(c));
literal s_eq_emp = mk_eq_empty(s);
add_axiom(s_eq_emp, mk_seq_eq(s, s1c));
add_axiom(s_eq_emp, ~mk_literal(seq.str.mk_contains(mk_concat(x, s1), s)));
}