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fixes for #4688

Browse source 
https://github.com/Z3Prover/z3/issues/4866#issuecomment-778721073
This commit is contained in:
Nikolaj Bjorner 2021-04-11 17:42:12 -07:00
parent 2dcfe799bc
commit 804f065215
4 changed files with 59 additions and 6 deletions
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34
src/ast/rewriter/seq_rewriter.cpp
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@ -1157,6 +1157,17 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
return BR_REWRITE3;
}
// (extract (extract a p l) 0 (len a)) -> (extract a p l)
if (str().is_extract(a, a1, b1, c1) && constantPos && pos == 0 && str().is_length(c, b1) && a1 == b1) {
result = a;
return BR_DONE;
}
// (extract (extract a p l) 0 l) -> (extract a p l)
if (str().is_extract(a, a1, b1, c1) && constantPos && pos == 0 && c == c1) {
result = a;
return BR_DONE;
}
// extract(extract(a, 3, 6), 1, len(extract(a, 3, 6)) - 1) -> extract(a, 4, 5)
if (str().is_extract(a, a1, b1, c1) && is_suffix(a, b, c) &&
@ -4382,6 +4393,29 @@ br_status seq_rewriter::reduce_re_eq(expr* l, expr* r, expr_ref& result) {
return BR_FAILED;
}
br_status seq_rewriter::mk_le_core(expr * l, expr * r, expr_ref & result) {
// k <= len(x) -> true if k <= 0
rational n;
if (str().is_length(r) && m_autil.is_numeral(l, n) && n <= 0) {
result = m().mk_true();
return BR_DONE;
}
// len(x) <= 0 -> x = ""
// len(x) <= k -> false if k < 0
expr* e = nullptr;
if (str().is_length(l, e) && m_autil.is_numeral(r, n)) {
if (n == 0)
result = str().mk_is_empty(e);
else if (n < 0)
result = m().mk_false();
else
return BR_FAILED;
return BR_REWRITE1;
}
return BR_FAILED;
}
br_status seq_rewriter::mk_eq_core(expr * l, expr * r, expr_ref & result) {
expr_ref_vector res(m());
expr_ref_pair_vector new_eqs(m());