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update handling of contains constraints taking string literals into account

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2017-08-12 19:14:55 -07:00
parent c0bd40c00a
commit c4083c367a
2 changed files with 44 additions and 2 deletions
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43
src/ast/rewriter/seq_rewriter.cpp
View file

@ -597,6 +597,45 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
return BR_FAILED;
}
bool seq_rewriter::cannot_contain_suffix(expr* a, expr* b) {
if (m_util.str.is_unit(a) && m_util.str.is_unit(b) && m().are_distinct(a, b)) {
return true;
}
zstring A, B;
if (m_util.str.is_string(a, A) && m_util.str.is_string(b, B)) {
// some prefix of a is a suffix of b
bool found = false;
for (unsigned i = 1; !found && i <= A.length(); ++i) {
found = A.extract(0, i).suffixof(B);
}
return !found;
}
return false;
}
bool seq_rewriter::cannot_contain_prefix(expr* a, expr* b) {
if (m_util.str.is_unit(a) && m_util.str.is_unit(b) && m().are_distinct(a, b)) {
return true;
}
zstring A, B;
if (m_util.str.is_string(a, A) && m_util.str.is_string(b, B)) {
// some suffix of a is a prefix of b
bool found = false;
for (unsigned i = 0; !found && i < A.length(); ++i) {
found = A.extract(i, A.length()-i).suffixof(B);
}
return !found;
}
return false;
}
br_status seq_rewriter::mk_seq_contains(expr* a, expr* b, expr_ref& result) {
zstring c, d;
if (m_util.str.is_string(a, c) && m_util.str.is_string(b, d)) {
@ -666,8 +705,8 @@ br_status seq_rewriter::mk_seq_contains(expr* a, expr* b, expr_ref& result) {
unsigned sz = as.size();
expr* b0 = bs[0].get();
expr* bL = bs[bs.size()-1].get();
for (; offs < as.size() && m_util.str.is_unit(b0) && m_util.str.is_unit(as[offs].get()) && m().are_distinct(b0, as[offs].get()); ++offs) {};
for (; sz > offs && m_util.str.is_unit(bL) && m_util.str.is_unit(as[sz-1].get()) && m().are_distinct(bL, as[sz-1].get()); --sz) {}
for (; offs < as.size() && cannot_contain_prefix(as[offs].get(), b0); ++offs) {}
for (; sz > offs && cannot_contain_suffix(as[sz-1].get(), bL); --sz) {}
if (offs == sz) {
result = m().mk_eq(b, m_util.str.mk_empty(m().get_sort(b)));
return BR_REWRITE2;

3
src/ast/rewriter/seq_rewriter.h
View file

@ -122,6 +122,9 @@ class seq_rewriter {
br_status mk_re_loop(unsigned num_args, expr* const* args, expr_ref& result);
br_status mk_re_range(expr* lo, expr* hi, expr_ref& result);
bool cannot_contain_prefix(expr* a, expr* b);
bool cannot_contain_suffix(expr* a, expr* b);
bool set_empty(unsigned sz, expr* const* es, bool all, expr_ref_vector& lhs, expr_ref_vector& rhs);
bool is_subsequence(unsigned n, expr* const* l, unsigned m, expr* const* r,
expr_ref_vector& lhs, expr_ref_vector& rhs, bool& is_sat);