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more rewrite rules

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This commit is contained in:
Nikolaj Bjorner 2021-02-17 17:31:46 -08:00
parent bcad4d9435
commit e63dc7efc2
5 changed files with 150 additions and 39 deletions
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49
src/ast/rewriter/seq_axioms.cpp
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@ -127,31 +127,34 @@ namespace seq {
auto s = purify(_s);
auto i = purify(_i);
auto l = purify(_l);
if (is_tail(s, i, l)) {
if (is_tail(s, _i, _l)) {
tail_axiom(e, s);
return;
}
if (is_drop_last(s, i, l)) {
if (is_drop_last(s, _i, _l)) {
drop_last_axiom(e, s);
return;
}
if (is_extract_prefix0(s, i, l)) {
if (is_extract_prefix0(s, _i, _l)) {
extract_prefix_axiom(e, s, l);
return;
}
if (is_extract_suffix(s, _i, _l)) {
return;
}
expr_ref x = m_sk.mk_pre(s, i);
expr_ref ls = mk_len(s);
expr_ref ls = mk_len(_s);
expr_ref lx = mk_len(x);
expr_ref le = mk_len(e);
expr_ref ls_minus_i_l(mk_sub(mk_sub(ls, i), l), m);
expr_ref ls_minus_i_l(mk_sub(mk_sub(ls, _i), _l), m);
expr_ref y = m_sk.mk_post(s, a.mk_add(i, l));
expr_ref xe = mk_concat(x, e);
expr_ref xey = mk_concat(x, e, y);
expr_ref zero(a.mk_int(0), m);
expr_ref i_ge_0 = mk_ge(i, 0);
expr_ref i_le_ls = mk_le(mk_sub(i, ls), 0);
expr_ref ls_le_i = mk_le(mk_sub(ls, i), 0);
expr_ref i_ge_0 = mk_ge(_i, 0);
expr_ref i_le_ls = mk_le(mk_sub(_i, ls), 0);
expr_ref ls_le_i = mk_le(mk_sub(ls, _i), 0);
expr_ref ls_ge_li = mk_ge(ls_minus_i_l, 0);
expr_ref l_ge_0 = mk_ge(l, 0);
expr_ref l_le_0 = mk_le(l, 0);
@ -224,6 +227,13 @@ namespace seq {
return a.is_numeral(i, i1) && i1.is_zero();
}
bool axioms::is_extract_suffix(expr* s, expr* i, expr* l) {
expr_ref len(a.mk_add(l, i), m);
m_rewrite(len);
return seq.str.is_length(len, l) && l == s;
}
/*
s = ey
l <= 0 => e = empty
@ -231,6 +241,7 @@ namespace seq {
len(s) < l => e = s
*/
void axioms::extract_prefix_axiom(expr* e, expr* s, expr* l) {
TRACE("seq", tout << "prefix " << mk_bounded_pp(e, m, 2) << " " << mk_bounded_pp(s, m, 2) << " " << mk_bounded_pp(l, m, 2) << "\n";);
expr_ref le = mk_len(e);
expr_ref ls = mk_len(s);
@ -244,6 +255,28 @@ namespace seq {
add_clause(l_le_s, mk_eq(e, s));
}
/*
s = xe
0 <= i <= len(s) => i = len(x)
i < 0 => e = empty
i > len(s) => e = empty
*/
void axioms::extract_suffix_axiom(expr* e, expr* s, expr* i) {
TRACE("seq", tout << "suffix " << mk_bounded_pp(e, m, 2) << " " << mk_bounded_pp(s, m, 2) << "\n";);
expr_ref x = m_sk.mk_pre(s, i);
expr_ref lx = mk_len(x);
expr_ref ls = mk_len(s);
expr_ref xe = mk_concat(x, e);
expr_ref emp = mk_eq_empty(e);
expr_ref i_ge_0 = mk_ge(i, 0);
expr_ref i_le_s = mk_le(mk_sub(i, ls), 0);
add_clause(mk_eq(s, xe));
add_clause(~i_ge_0, ~i_le_s, mk_eq(i, lx));
add_clause(i_ge_0, emp);
add_clause(i_le_s, emp);
}
/*
encode that s is not contained in of xs1
where s1 is all of s, except the last element.