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re.range with non-unit arguments is the empty language (#4360)

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Murphy Berzish 2020-05-17 21:08:50 -05:00 • committed by GitHub
parent 152d6338f8
commit 1c760b04cf
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2 changed files with 14 additions and 7 deletions
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3
src/ast/rewriter/seq_rewriter.cpp
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@ -308,7 +308,8 @@ eautomaton* re2automaton::re2aut(expr* e) {
return a.detach();
}
else {
TRACE("seq", tout << "Range expression is not handled: " << mk_pp(e, m) << "\n";);
// if e1/e2 are not unit, (re.range e1 e2) is defined to be the empty language
return alloc(eautomaton, sm);
}
}
else if (u.re.is_complement(e, e0) && (a = re2aut(e0)) && m_sa) {

18
src/smt/theory_str_regex.cpp
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@ -812,9 +812,11 @@ namespace smt {
zstring str1, str2;
u.str.is_string(sub1, str1);
u.str.is_string(sub2, str2);
SASSERT(str1.length() == 1);
SASSERT(str2.length() == 1);
return 1 + str2[0] - str1[0];
if (str1.length() == 1 && str2.length() == 1) {
return 1 + str2[0] - str1[0];
} else {
return 1;
}
} else if (u.re.is_full_char(re) || u.re.is_full_seq(re)) {
return 1;
} else {
@ -964,9 +966,13 @@ namespace smt {
zstring str1, str2;
u.str.is_string(sub1, str1);
u.str.is_string(sub2, str2);
SASSERT(str1.length() == 1);
SASSERT(str2.length() == 1);
lens.insert(1);
// re.range is a language of singleton strings if both of its arguments are;
// otherwise it is the empty language
if (str1.length() == 1 && str2.length() == 1) {
lens.insert(1);
} else {
lens.insert(0);
}
} else if (u.re.is_full_char(re)) {
lens.insert(1);
} else if (u.re.is_full_seq(re)) {