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fix #2035 regression. correct axiom is |extract(s,i,l)| <= l or l < 0, but it is subsumed by encoding of extract, so new axiom is not useful

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2018-12-11 20:27:28 -08:00
parent c1b03e8ca6
commit b3d0ed6143
1 changed files with 1 additions and 6 deletions
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7
src/smt/theory_seq.cpp
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@ -4454,7 +4454,6 @@ expr_ref theory_seq::add_elim_string_axiom(expr* n) {
- len(str) = str.length() if x = str
- len(empty) = 0 if x = empty
- len(int.to.str(i)) >= 1 if x = int.to.str(i) and more generally if i = 0 then 1 else 1+floor(log(|i|))
- len(substr(s,i,l)) <= l if x = substr(s,i,l)
- len(x) >= 0 otherwise
*/
void theory_seq::add_length_axiom(expr* n) {
@ -4474,11 +4473,6 @@ void theory_seq::add_length_axiom(expr* n) {
add_itos_length_axiom(n);
}
else {
expr* s = nullptr, *i = nullptr, *l = nullptr;
if (m_util.str.is_extract(x, s, i, l)) {
literal len_le_l = mk_simplified_literal(m_autil.mk_ge(mk_sub(l, n), m_autil.mk_int(0)));
add_axiom(len_le_l);
}
add_axiom(mk_literal(m_autil.mk_ge(n, m_autil.mk_int(0))));
}
if (!ctx.at_base_level()) {
@ -4801,6 +4795,7 @@ void theory_seq::add_extract_axiom(expr* e) {
add_extract_suffix_axiom(e, s, i);
return;
}
expr_ref x(mk_skolem(m_pre, s, i), m);
expr_ref ls = mk_len(s);
expr_ref lx = mk_len(x);