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add partial support for complementation of regular expressions. Handles case of complementing character ranges

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2016-02-12 15:59:33 +00:00
parent 9dbb8057ca
commit 94453033b6
4 changed files with 93 additions and 6 deletions
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63
src/ast/rewriter/seq_rewriter.cpp
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@ -83,7 +83,7 @@ eautomaton* re2automaton::operator()(expr* e) {
eautomaton* re2automaton::re2aut(expr* e) {
SASSERT(u.is_re(e));
expr* e1, *e2;
expr *e0, *e1, *e2;
scoped_ptr<eautomaton> a, b;
unsigned lo, hi;
zstring s1, s2;
@ -98,8 +98,7 @@ eautomaton* re2automaton::re2aut(expr* e) {
}
else if (u.re.is_star(e, e1) && (a = re2aut(e1))) {
a->add_final_to_init_moves();
a->add_init_to_final_states();
a->add_init_to_final_states();
return a.detach();
}
else if (u.re.is_plus(e, e1) && (a = re2aut(e1))) {
@ -116,8 +115,6 @@ eautomaton* re2automaton::re2aut(expr* e) {
unsigned start = s1[0];
unsigned stop = s2[0];
unsigned nb = s1.num_bits();
sort_ref s(bv.mk_sort(nb), m);
expr_ref v(m.mk_var(0, s), m);
expr_ref _start(bv.mk_numeral(start, nb), m);
expr_ref _stop(bv.mk_numeral(stop, nb), m);
a = alloc(eautomaton, sm, sym_expr::mk_range(_start, _stop));
@ -127,6 +124,39 @@ eautomaton* re2automaton::re2aut(expr* e) {
TRACE("seq", tout << "Range expression is not handled: " << mk_pp(e, m) << "\n";);
}
}
else if (u.re.is_complement(e, e0)) {
if (u.re.is_range(e0, e1, e2) && u.str.is_string(e1, s1) && u.str.is_string(e2, s2) &&
s1.length() == 1 && s2.length() == 1) {
unsigned start = s1[0];
unsigned stop = s2[0];
unsigned nb = s1.num_bits();
sort_ref s(bv.mk_sort(nb), m);
expr_ref v(m.mk_var(0, s), m);
expr_ref _start(bv.mk_numeral(start, nb), m);
expr_ref _stop(bv.mk_numeral(stop, nb), m);
expr_ref _pred(m.mk_not(m.mk_and(bv.mk_ule(_start, v), bv.mk_ule(v, _stop))), m);
a = alloc(eautomaton, sm, sym_expr::mk_pred(_pred));
return a.detach();
}
else if (u.re.is_to_re(e0, e1) && u.str.is_string(e1, s1) && s1.length() == 1) {
unsigned nb = s1.num_bits();
sort_ref s(bv.mk_sort(nb), m);
expr_ref v(m.mk_var(0, s), m);
expr_ref _ch(bv.mk_numeral(s1[0], nb), m);
expr_ref _pred(m.mk_not(m.mk_eq(v, _ch)), m);
a = alloc(eautomaton, sm, sym_expr::mk_pred(_pred));
return a.detach();
}
else if (u.re.is_to_re(e0, e1) && u.str.is_unit(e1, e2)) {
expr_ref v(m.mk_var(0, m.get_sort(e2)), m);
expr_ref _pred(m.mk_not(m.mk_eq(v, e2)), m);
a = alloc(eautomaton, sm, sym_expr::mk_pred(_pred));
return a.detach();
}
else {
TRACE("seq", tout << "Complement expression is not handled: " << mk_pp(e, m) << "\n";);
}
}
else if (u.re.is_loop(e, e1, lo, hi) && (a = re2aut(e1))) {
scoped_ptr<eautomaton> eps = eautomaton::mk_epsilon(sm);
b = eautomaton::mk_epsilon(sm);
@ -225,6 +255,9 @@ br_status seq_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * con
case OP_RE_INTERSECT:
SASSERT(num_args == 2);
return mk_re_inter(args[0], args[1], result);
case OP_RE_COMPLEMENT:
SASSERT(num_args == 1);
return mk_re_complement(args[0], result);
case OP_RE_LOOP:
return mk_re_loop(num_args, args, result);
case OP_RE_EMPTY_SET:
@ -967,6 +1000,26 @@ br_status seq_rewriter::mk_re_union(expr* a, expr* b, expr_ref& result) {
return BR_FAILED;
}
br_status seq_rewriter::mk_re_complement(expr* a, expr_ref& result) {
expr* e1, *e2;
if (m_util.re.is_intersection(a, e1, e2)) {
result = m_util.re.mk_union(m_util.re.mk_complement(e1), m_util.re.mk_complement(e2));
return BR_REWRITE2;
}
if (m_util.re.is_union(a, e1, e2)) {
result = m_util.re.mk_inter(m_util.re.mk_complement(e1), m_util.re.mk_complement(e2));
return BR_REWRITE2;
}
if (m_util.re.is_empty(a)) {
result = m_util.re.mk_full(m().get_sort(a));
return BR_DONE;
}
if (m_util.re.is_full(a)) {
result = m_util.re.mk_empty(m().get_sort(a));
return BR_DONE;
}
return BR_FAILED;
}
/**
(emp n r) = emp