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strengthen support for int.to.str and length reasoning. Issue #589

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2016-05-28 12:26:47 -07:00
parent 8c99d3c431
commit c3f498a640
9 changed files with 103 additions and 31 deletions
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57
src/smt/theory_seq.cpp
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@ -1398,7 +1398,9 @@ bool theory_seq::is_var(expr* a) {
!m_util.str.is_concat(a) &&
!m_util.str.is_empty(a) &&
!m_util.str.is_string(a) &&
!m_util.str.is_unit(a);
!m_util.str.is_unit(a) &&
!m_util.str.is_itos(a) &&
!m.is_ite(a);
}
@ -2216,7 +2218,10 @@ bool theory_seq::add_itos_axiom(expr* e) {
m_itos_axioms.insert(val);
app_ref e1(m_util.str.mk_string(symbol(val.to_string().c_str())), m);
expr_ref n1(arith_util(m).mk_numeral(val, true), m);
add_axiom(mk_eq(m_util.str.mk_itos(n1), e1, false));
add_axiom(~mk_eq(n1, n , false), mk_eq(e, e1, false));
add_axiom(mk_eq(n1, n, false), ~mk_eq(e, e1, false));
m_trail_stack.push(insert_map<theory_seq, rational_set, rational>(m_itos_axioms, val));
m_trail_stack.push(push_replay(alloc(replay_axiom, m, e)));
return true;
@ -2883,7 +2888,7 @@ void theory_seq::add_length_axiom(expr* n) {
add_axiom(mk_eq(len, n, false));
}
else if (m_util.str.is_itos(x)) {
add_axiom(mk_literal(m_autil.mk_ge(n, m_autil.mk_int(1))));
add_itos_length_axiom(n);
}
else {
add_axiom(mk_literal(m_autil.mk_ge(n, m_autil.mk_int(0))));
@ -2891,6 +2896,52 @@ void theory_seq::add_length_axiom(expr* n) {
if (!ctx.at_base_level()) {
m_trail_stack.push(push_replay(alloc(replay_axiom, m, n)));
}
}
void theory_seq::add_itos_length_axiom(expr* len) {
expr* x, *n;
VERIFY(m_util.str.is_length(len, x));
VERIFY(m_util.str.is_itos(x, n));
add_axiom(mk_literal(m_autil.mk_ge(len, m_autil.mk_int(1))));
rational val;
if (get_value(n, val)) {
bool neg = val.is_neg();
rational ten(10);
if (neg) val.neg();
unsigned num_char = neg?2:1;
// 0 < x < 10
// 10 < x < 100
// 100 < x < 1000
rational hi(10);
while (val > hi) {
++num_char;
hi *= ten;
}
rational lo(div(hi - rational(1), ten));
literal len_le(mk_literal(m_autil.mk_ge(len, m_autil.mk_int(num_char))));
literal len_ge(mk_literal(m_autil.mk_le(len, m_autil.mk_int(num_char))));
if (neg) {
// n <= -lo => len >= num_char
// -hi < n <= 0 => len <= num_char
// n <= -hi or ~(n <= 0) or len <= num_char
literal l1(mk_literal(m_autil.mk_le(n, m_autil.mk_numeral(-lo, true))));
add_axiom(~l1, len_ge);
literal l3(mk_literal(m_autil.mk_le(n, m_autil.mk_numeral(-hi, true))));
literal l4(mk_literal(m_autil.mk_le(n, m_autil.mk_int(0))));
add_axiom(l3, ~l4, len_le);
}
else {
// n >= lo => len >= num_char
// 0 <= n < hi => len <= num_char
literal l1(mk_literal(m_autil.mk_ge(n, m_autil.mk_numeral(lo, true))));
add_axiom(~l1, len_ge);
literal l3(mk_literal(m_autil.mk_ge(n, m_autil.mk_numeral(hi, true))));
literal l4(mk_literal(m_autil.mk_ge(n, m_autil.mk_int(0))));
add_axiom(l3, ~l4, len_le);
}
}
}