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fix #2892

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2020-01-27 20:59:02 -08:00
parent ca11dc1fc5
commit ee62f83131
3 changed files with 46 additions and 13 deletions
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31
src/ast/rewriter/seq_rewriter.cpp
View file

@ -526,6 +526,10 @@ br_status seq_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * con
SASSERT(num_args == 2);
st = mk_str_le(args[0], args[1], result);
break;
case OP_STRING_LT:
SASSERT(num_args == 2);
st = mk_str_lt(args[0], args[1], result);
break;
case OP_STRING_CONST:
return BR_FAILED;
case OP_STRING_ITOS:
@ -1435,7 +1439,32 @@ br_status seq_rewriter::mk_seq_suffix(expr* a, expr* b, expr_ref& result) {
br_status seq_rewriter::mk_str_le(expr* a, expr* b, expr_ref& result) {
result = m().mk_not(m_util.str.mk_lex_lt(b, a));
return BR_DONE;
return BR_REWRITE2;
}
br_status seq_rewriter::mk_str_lt(expr* a, expr* b, expr_ref& result) {
zstring as, bs;
if (m_util.str.is_string(a, as) && m_util.str.is_string(b, bs)) {
unsigned sz = std::min(as.length(), bs.length());
for (unsigned i = 0; i < sz; ++i) {
if (as[i] < bs[i]) {
result = m().mk_true();
return BR_DONE;
}
if (as[i] > bs[i]) {
result = m().mk_false();
return BR_DONE;
}
}
if (sz <= as.length()) {
result = m().mk_false();
}
else {
result = m().mk_true();
}
return BR_DONE;
}
return BR_FAILED;
}
br_status seq_rewriter::mk_str_itos(expr* a, expr_ref& result) {

1
src/ast/rewriter/seq_rewriter.h
View file

@ -126,6 +126,7 @@ class seq_rewriter {
br_status mk_str_in_regexp(expr* a, expr* b, expr_ref& result);
br_status mk_str_to_regexp(expr* a, expr_ref& result);
br_status mk_str_le(expr* a, expr* b, expr_ref& result);
br_status mk_str_lt(expr* a, expr* b, expr_ref& result);
br_status mk_re_concat(expr* a, expr* b, expr_ref& result);
br_status mk_re_union(expr* a, expr* b, expr_ref& result);
br_status mk_re_inter(expr* a, expr* b, expr_ref& result);

27
src/smt/theory_seq.cpp
View file

@ -6490,12 +6490,13 @@ void theory_seq::add_unit_axiom(expr* n) {
}
/**
e1 < e2 => e1 = empty or e1 = xcy
e1 < e2 => e1 = empty or c < d
e1 < e2 => e2 = xdz
!(e1 < e2) => e1 = e2 or e2 = empty or e2 = xdz
!(e1 < e2) => e1 = e2 or e2 = empty or d < c
!(e1 < e2) => e1 = e2 or e1 = xcy
e1 < e2 => prefix(e1, e2) or e1 = xcy
e1 < e2 => prefix(e1, e2) or c < d
e1 < e2 => prefix(e1, e2) or e2 = xdz
e1 < e2 => e1 != e2
!(e1 < e2) => prefix(e2, e1) or e2 = xdz
!(e1 < e2) => prefix(e2, e1) or d < c
!(e1 < e2) => prefix(e2, e1) or e1 = xcy
!(e1 = e2) or !(e1 < e2)
optional:
@ -6521,16 +6522,18 @@ void theory_seq::add_lt_axiom(expr* n) {
literal emp1 = mk_eq(e1, empty_string, false);
literal emp2 = mk_eq(e2, empty_string, false);
literal eq = mk_eq(e1, e2, false);
literal pref21 = mk_literal(m_util.str.mk_prefix(e2, e1));
literal pref12 = mk_literal(m_util.str.mk_prefix(e1, e2));
literal e1xcy = mk_eq(e1, xcy, false);
literal e2xdz = mk_eq(e2, xdz, false);
literal ltcd = mk_literal(m_util.mk_lt(c, d));
literal ltdc = mk_literal(m_util.mk_lt(d, c));
add_axiom(~lt, e2xdz);
add_axiom(~lt, emp1, e1xcy);
add_axiom(~lt, emp1, ltcd);
add_axiom(lt, eq, e1xcy);
add_axiom(lt, eq, emp2, ltdc);
add_axiom(lt, eq, emp2, e2xdz);
add_axiom(~lt, pref12, e2xdz);
add_axiom(~lt, pref12, e1xcy);
add_axiom(~lt, pref12, ltcd);
add_axiom(lt, pref21, e1xcy);
add_axiom(lt, pref21, ltdc);
add_axiom(lt, pref21, e2xdz);
add_axiom(~eq, ~lt);
}