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implementing last-index-of #2089

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2019-03-22 12:29:34 -07:00
parent 62ec02e50f
commit 3c8fd83c97
10 changed files with 174 additions and 31 deletions
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45
src/smt/theory_seq.cpp
View file

@ -4150,6 +4150,12 @@ expr_ref theory_seq::expand1(expr* e0, dependency*& eqs) {
if (!arg1 || !arg2) return result;
result = m_util.str.mk_index(arg1, arg2, e3);
}
else if (m_util.str.is_last_index(e, e1, e2)) {
arg1 = try_expand(e1, deps);
arg2 = try_expand(e2, deps);
if (!arg1 || !arg2) return result;
result = m_util.str.mk_last_index(arg1, arg2);
}
else if (m.is_ite(e, e1, e2, e3)) {
if (ctx.e_internalized(e) && ctx.e_internalized(e2) && ctx.get_enode(e)->get_root() == ctx.get_enode(e2)->get_root()) {
result = try_expand(e2, deps);
@ -4288,6 +4294,9 @@ void theory_seq::deque_axiom(expr* n) {
else if (m_util.str.is_index(n)) {
add_indexof_axiom(n);
}
else if (m_util.str.is_last_index(n)) {
add_last_indexof_axiom(n);
}
else if (m_util.str.is_replace(n)) {
add_replace_axiom(n);
}
@ -4437,6 +4446,42 @@ void theory_seq::add_indexof_axiom(expr* i) {
}
}
/**
!contains(t, s) => i = -1
|t| = 0 => |s| = 0 or i = -1
|t| = 0 & |s| = 0 => i = 0
|t| != 0 & contains(t, s) => t = xsy & i = len(x)
|s| = 0 or s = s_head*s_tail
|s| = 0 or !contains(s_tail*y, s)
*/
void theory_seq::add_last_indexof_axiom(expr* i) {
expr* s = nullptr, *t = nullptr;
VERIFY(m_util.str.is_last_index(i, t, s));
expr_ref minus_one(m_autil.mk_int(-1), m);
expr_ref zero(m_autil.mk_int(0), m);
expr_ref s_head(m), s_tail(m);
expr_ref x = mk_skolem(symbol("seq.last_indexof_left"), t, s);
expr_ref y = mk_skolem(symbol("seq.last_indexof_right"), t, s);
mk_decompose(s, s_head, s_tail);
literal cnt = mk_literal(m_util.str.mk_contains(t, s));
literal cnt2 = mk_literal(m_util.str.mk_contains(mk_concat(s_tail, y), s));
literal i_eq_m1 = mk_eq(i, minus_one, false);
literal i_eq_0 = mk_eq(i, zero, false);
literal s_eq_empty = mk_eq_empty(s);
literal t_eq_empty = mk_eq_empty(t);
expr_ref xsy = mk_concat(x, s, y);
add_axiom(cnt, i_eq_m1);
add_axiom(~t_eq_empty, s_eq_empty, i_eq_m1);
add_axiom(~t_eq_empty, ~s_eq_empty, i_eq_0);
add_axiom(t_eq_empty, ~cnt, mk_seq_eq(t, xsy));
add_axiom(t_eq_empty, ~cnt, mk_eq(i, mk_len(x), false));
add_axiom(s_eq_empty, mk_eq(s, mk_concat(s_head, s_tail), false));
add_axiom(s_eq_empty, ~cnt2);
}
/*
let r = replace(a, s, t)

1
src/smt/theory_seq.h
View file

@ -550,6 +550,7 @@ namespace smt {
void push_lit_as_expr(literal l, expr_ref_vector& buf);
void add_axiom(literal l1, literal l2 = null_literal, literal l3 = null_literal, literal l4 = null_literal, literal l5 = null_literal);
void add_indexof_axiom(expr* e);
void add_last_indexof_axiom(expr* e);
void add_replace_axiom(expr* e);
void add_extract_axiom(expr* e);
void add_length_axiom(expr* n);