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prepare for alternative axiom

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This commit is contained in:
Nikolaj Bjorner 2020-07-25 15:10:39 -07:00
parent 2d4839f89e
commit f789573d12
1 changed files with 14 additions and 2 deletions
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16
src/smt/seq_axioms.cpp
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@ -325,17 +325,29 @@ void seq_axioms::add_indexof_axiom(expr* i) {
add_axiom(~t_eq_empty, s_eq_empty, i_eq_m1);
if (!offset || (a.is_numeral(offset, r) && r.is_zero())) {
// |s| = 0 => indexof(t,s,0) = 0
add_axiom(~s_eq_empty, i_eq_0);
#if 1
expr_ref x = m_sk.mk_indexof_left(t, s);
expr_ref y = m_sk.mk_indexof_right(t, s);
xsy = mk_concat(x, s, y);
expr_ref lenx = mk_len(x);
// |s| = 0 => indexof(t,s,0) = 0
// contains(t,s) & |s| != 0 => t = xsy & indexof(t,s,0) = |x|
add_axiom(~s_eq_empty, i_eq_0);
add_axiom(~cnt, s_eq_empty, mk_seq_eq(t, xsy));
add_axiom(~cnt, s_eq_empty, mk_eq(i, lenx));
add_axiom(~cnt, mk_ge(i, 0));
tightest_prefix(s, x);
#else
// let i := indexof(t,s,0)
// contains(t, s) & |s| != 0 => ~contains(substr(t,0,i+len(s)-1), s)
// => substr(t,0,i+len(s)) = substr(t,0,i) ++ s
//
expr_ref len_s = mk_len(s);
expr_ref mone(a.mk_int(-1), m);
add_axiom(~cnt, s_eq_empty, ~mk_literal(seq.str.mk_contains(seq.str.mk_substr(t,zero,a.mk_add(i,len_s,mone)),s)));
add_axiom(~cnt, s_eq_empty, mk_seq_eq(seq.str.mk_substr(t,zero,a.mk_add(i,len_s)),
seq.str.mk_concat(seq.str.mk_substr(t,zero,i), s)));
#endif
}
else {
// offset >= len(t) => |s| = 0 or indexof(t, s, offset) = -1