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Merge pull request #1220 from mtrberzi/regex-fixes

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Small regex fixes in theory_str
This commit is contained in:
Nikolaj Bjorner 2017-08-20 08:01:59 -07:00 • committed by GitHub
commit 04084e21c8
1 changed files with 48 additions and 17 deletions
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65
src/smt/theory_str.cpp
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@ -1683,6 +1683,8 @@ namespace smt {
u.str.is_string(range1, range1val);
u.str.is_string(range2, range2val);
return zstring("[") + range1val + zstring("-") + range2val + zstring("]");
} else if (u.re.is_full(a_regex)) {
return zstring("(.*)");
} else {
TRACE("str", tout << "BUG: unrecognized regex term " << mk_pp(regex, get_manager()) << std::endl;);
UNREACHABLE(); return zstring("");
@ -1713,6 +1715,12 @@ namespace smt {
expr_ref str(ex->get_arg(0), m);
app * regex = to_app(ex->get_arg(1));
// quick reference for the following code:
// - ex: top-level regex membership term
// - str: string term appearing in ex
// - regex: regex term appearing in ex
// ex ::= (str.in.re str regex)
if (u.re.is_to_re(regex)) {
expr_ref rxStr(regex->get_arg(0), m);
// want to assert 'expr IFF (str == rxStr)'
@ -1792,6 +1800,9 @@ namespace smt {
expr_ref finalAxiom(m.mk_iff(ex, rhs), m);
SASSERT(finalAxiom);
assert_axiom(finalAxiom);
} else if (u.re.is_full(regex)) {
// trivially true for any string!
assert_axiom(ex);
} else {
TRACE("str", tout << "ERROR: unknown regex expression " << mk_pp(regex, m) << "!" << std::endl;);
NOT_IMPLEMENTED_YET();
@ -6192,24 +6203,31 @@ namespace smt {
expr * arg_str = a->get_arg(0);
zstring str;
if (u.str.is_string(arg_str, str)) {
TRACE("str", tout << "build NFA for '" << str << "'" << "\n";);
/*
* For an n-character string, we make (n-1) intermediate states,
* labelled i_(0) through i_(n-2).
* Then we construct the following transitions:
* start --str[0]--> i_(0) --str[1]--> i_(1) --...--> i_(n-2) --str[n-1]--> final
*/
unsigned last = start;
for (int i = 0; i <= ((int)str.length()) - 2; ++i) {
unsigned i_state = next_id();
make_transition(last, str[i], i_state);
TRACE("str", tout << "string transition " << last << "--" << str[i] << "--> " << i_state << "\n";);
last = i_state;
if (str.length() == 0) {
// transitioning on the empty string is handled specially
TRACE("str", tout << "empty string epsilon-move " << start << " --> " << end << std::endl;);
make_epsilon_move(start, end);
} else {
TRACE("str", tout << "build NFA for '" << str << "'" << "\n";);
/*
* For an n-character string, we make (n-1) intermediate states,
* labelled i_(0) through i_(n-2).
* Then we construct the following transitions:
* start --str[0]--> i_(0) --str[1]--> i_(1) --...--> i_(n-2) --str[n-1]--> final
*/
unsigned last = start;
for (int i = 0; i <= ((int)str.length()) - 2; ++i) {
unsigned i_state = next_id();
make_transition(last, str[i], i_state);
TRACE("str", tout << "string transition " << last << "--" << str[i] << "--> " << i_state << "\n";);
last = i_state;
}
make_transition(last, str[(str.length() - 1)], end);
TRACE("str", tout << "string transition " << last << "--" << str[(str.length() - 1)] << "--> " << end << "\n";);
}
make_transition(last, str[(str.length() - 1)], end);
TRACE("str", tout << "string transition " << last << "--" << str[(str.length() - 1)] << "--> " << end << "\n";);
} else {
TRACE("str", tout << "invalid string constant in Str2Reg" << std::endl;);
} else { // ! u.str.is_string(arg_str, str)
TRACE("str", tout << "WARNING: invalid string constant in str.to.re! Cancelling." << std::endl;);
u.get_manager().raise_exception("invalid term in str.to.re, argument must be a string constant");
m_valid = false;
return;
}
@ -6281,6 +6299,19 @@ namespace smt {
}
TRACE("str", tout << "range NFA: start = " << start << ", end = " << end << std::endl;);
} else if (u.re.is_full(e)) {
// effectively the same as .* where . can be any single character
// start --e--> tmp
// tmp --e--> end
// tmp --C--> tmp for every character C
unsigned tmp = next_id();
make_epsilon_move(start, tmp);
make_epsilon_move(tmp, end);
for (unsigned int i = 0; i < 256; ++i) {
char ch = (char)i;
make_transition(tmp, ch, tmp);
}
TRACE("str", tout << "re.all NFA: start = " << start << ", end = " << end << std::endl;);
} else {
TRACE("str", tout << "invalid regular expression" << std::endl;);
m_valid = false;