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augment axiomatization for substr to fix #2366

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2019-07-12 08:38:33 +01:00
parent cfb4d289b8
commit 1ba6d16c61
1 changed files with 3 additions and 2 deletions
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5
src/smt/theory_seq.cpp
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@ -2481,6 +2481,7 @@ bool theory_seq::is_var(expr* a) const {
!m_util.str.is_string(a) &&
!m_util.str.is_unit(a) &&
!m_util.str.is_itos(a) &&
// !m_util.str.is_extract(a) &&
!m.is_ite(a);
}
@ -4941,6 +4942,7 @@ this translates to:
i >= |s| => |e| = 0
i < 0 => |e| = 0
l <= 0 => |e| = 0
|e| = 0 => i < 0 | l <= 0 | i >= |s|
It follows that:
|e| = min(l, |s| - i) for 0 <= i < |s| and 0 < |l|
@ -4952,7 +4954,6 @@ void theory_seq::add_extract_axiom(expr* e) {
TRACE("seq", tout << mk_pp(e, m) << "\n";);
expr* s = nullptr, *i = nullptr, *l = nullptr;
VERIFY(m_util.str.is_extract(e, s, i, l));
#if 0
if (is_tail(s, i, l)) {
add_tail_axiom(e, s);
return;
@ -4969,7 +4970,6 @@ void theory_seq::add_extract_axiom(expr* e) {
add_extract_suffix_axiom(e, s, i);
return;
}
#endif
expr_ref x(mk_skolem(m_pre, s, i), m);
expr_ref ls = mk_len(s);
expr_ref lx = mk_len(x);
@ -4995,6 +4995,7 @@ void theory_seq::add_extract_axiom(expr* e) {
add_axiom(i_ge_0, le_is_0);
add_axiom(ls_le_i, le_is_0);
add_axiom(~ls_le_0, le_is_0);
add_axiom(~le_is_0, ~i_ge_0, ~ls_le_i, ls_le_0);
}
void theory_seq::add_tail_axiom(expr* e, expr* s) {