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detect unit('a') in addition to a

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2026-06-25 20:15:13 -07:00
parent c530faab4e
commit ee6e4e2821
1 changed files with 36 additions and 11 deletions
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47
src/ast/rewriter/seq_rewriter.cpp
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@ -4117,14 +4117,10 @@ br_status seq_rewriter::mk_re_star(expr* a, expr_ref& result) {
*/
br_status seq_rewriter::mk_re_range(expr* lo, expr* hi, expr_ref& result) {
zstring slo, shi;
unsigned clo, chi;
expr *lo1, *hi1;
unsigned len = 0;
bool is_empty = false;
if (str().is_string(lo, slo) && slo.length() != 1)
is_empty = true;
if (str().is_string(hi, shi) && shi.length() != 1)
is_empty = true;
if (slo.length() == 1 && shi.length() == 1 && slo[0] > shi[0])
is_empty = true;
len = min_length(lo).second;
if (len > 1)
is_empty = true;
@ -4135,16 +4131,45 @@ br_status seq_rewriter::mk_re_range(expr* lo, expr* hi, expr_ref& result) {
is_empty = true;
if (max_length(hi) == std::make_pair(true, rational(0)))
is_empty = true;
if (!is_empty) {
if (str().is_string(lo, slo)) {
if (slo.length() != 1)
is_empty = true;
else
clo = slo[0];
}
else if (str().is_unit(lo, lo1) && m_util.is_const_char(lo1, clo))
;
else
is_empty = true;
}
if (!is_empty) {
if (str().is_string(hi, shi)) {
if (shi.length() != 1)
is_empty = true;
else
chi = shi[0];
}
else if (str().is_unit(hi, hi1) && m_util.is_const_char(hi1, chi))
;
else
is_empty = true;
}
if (clo > chi)
is_empty = true;
// Singleton: re.range "a" "a" → str.to_re "a"
if (clo == chi) {
result = re().mk_to_re(str().mk_string(slo));
return BR_DONE;
}
if (is_empty) {
sort* srt = re().mk_re(lo->get_sort());
result = re().mk_empty(srt);
return BR_DONE;
}
// Singleton: re.range "a" "a" → str.to_re "a"
if (slo.length() == 1 && shi.length() == 1 && slo[0] == shi[0]) {
result = re().mk_to_re(lo);
return BR_DONE;
}
return BR_FAILED;
}