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fix #4478

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2020-05-31 11:16:11 -07:00
parent 31e75d1401
commit 7f7663a3b4
3 changed files with 26 additions and 3 deletions
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26
src/ast/rewriter/seq_rewriter.cpp
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@ -735,6 +735,12 @@ br_status seq_rewriter::mk_seq_unit(expr* e, expr_ref& result) {
"" + a = a
string + (string + a) = string + a
*/
expr_ref seq_rewriter::mk_seq_concat(expr* a, expr* b) {
expr_ref result(m());
if (BR_FAILED == mk_seq_concat(a, b, result))
result = str().mk_concat(a, b);
return result;
}
br_status seq_rewriter::mk_seq_concat(expr* a, expr* b, expr_ref& result) {
zstring s1, s2;
expr* c, *d;
@ -2074,7 +2080,7 @@ bool seq_rewriter::get_head_tail(expr* s, expr_ref& head, expr_ref& tail) {
return true;
}
if (str().is_concat(s, h, t) && get_head_tail(h, head, tail)) {
tail = str().mk_concat(tail, t);
tail = mk_seq_concat(tail, t);
return true;
}
return false;
@ -2097,7 +2103,7 @@ bool seq_rewriter::get_head_tail_reversed(expr* s, expr_ref& head, expr_ref& tai
return true;
}
if (str().is_concat(s, h, t) && get_head_tail_reversed(t, head, tail)) {
head = str().mk_concat(h, head);
head = mk_seq_concat(h, head);
return true;
}
return false;
@ -2179,6 +2185,7 @@ br_status seq_rewriter::mk_re_reverse(expr* r, expr_ref& result) {
sort* seq_sort = nullptr;
VERIFY(m_util.is_re(r, seq_sort));
expr* r1 = nullptr, *r2 = nullptr, *p = nullptr, *s = nullptr;
expr* s1 = nullptr, *s2 = nullptr;
zstring zs;
unsigned lo = 0, hi = 0;
if (re().is_concat(r, r1, r2)) {
@ -2241,6 +2248,15 @@ br_status seq_rewriter::mk_re_reverse(expr* r, expr_ref& result) {
result = re().mk_to_re(str().mk_string(zs.reverse()));
return BR_DONE;
}
else if (re().is_to_re(r, s) && str().is_unit(s)) {
result = r;
return BR_DONE;
}
else if (re().is_to_re(r, s) && str().is_concat(s, s1, s2)) {
result = re().mk_concat(re().mk_reverse(re().mk_to_re(s2)),
re().mk_reverse(re().mk_to_re(s1)));
return BR_REWRITE3;
}
else {
// stuck cases: variable, re().is_to_re, re().is_derivative, ...
return BR_FAILED;
@ -2402,6 +2418,12 @@ br_status seq_rewriter::mk_re_derivative(expr* ele, expr* r, expr_ref& result) {
return BR_DONE;
}
}
expr* e1 = nullptr, *e2 = nullptr;
if (str().is_unit(r1, e1) && str().is_unit(r2, e2)) {
result = m().mk_and(m_util.mk_le(e1, ele), m_util.mk_le(ele, e2));
result = re_predicate(result, seq_sort);
return BR_REWRITE2;
}
}
else if (re().is_full_char(r)) {
result = re().mk_to_re(str().mk_empty(seq_sort));