mirrors/z3
3
0
Fork 0
mirror of https://github.com/Z3Prover/z3 synced 2025-04-27 10:55:50 +00:00
Code Activity

#5591

Browse source 
nth issue
This commit is contained in:
Nikolaj Bjorner 2021-10-12 13:59:28 -07:00
parent 58fd4fc860
commit 9a76bf0aa2
2 changed files with 19 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

26
src/ast/rewriter/seq_rewriter.cpp
View file

@ -1603,23 +1603,33 @@ br_status seq_rewriter::mk_seq_nth(expr* a, expr* b, expr_ref& result) {
result = s;
return BR_DONE;
}
if (str().is_extract(a, s, p, len) && m_autil.is_numeral(p, pos1)) {
if (str().is_extract(a, s, p, len) && m_autil.is_numeral(p, pos1) && pos1 > 0) {
expr_ref_vector lens(m());
rational pos2;
/*
* nth(s[k, |s| - k], b) =
* b < 0 -> nth_u(a, b)
* b + k < |s| -> nth(s, b + k)
* k >= |s| -> nth_u(empty, b)
* k < |s| <= b + k -> nth_u(a, b)
*/
if (get_lengths(len, lens, pos2) && (pos1 == -pos2) && (lens.size() == 1) && (lens.get(0) == s)) {
expr_ref idx(m_autil.mk_int(pos1), m());
idx = m_autil.mk_add(b, idx);
expr* es[2] = { s, idx };
result = m().mk_app(m_util.get_family_id(), OP_SEQ_NTH, 2, es);
expr_ref k(m_autil.mk_int(pos1), m());
expr_ref case1(str().mk_nth_i(s, m_autil.mk_add(b, k)), m());
expr_ref case2(str().mk_nth_u(str().mk_empty(s->get_sort()), b), m());
expr_ref case3(str().mk_nth_u(a, b), m());
result = case3;
result = m().mk_ite(m_autil.mk_lt(m_autil.mk_add(k, b), str().mk_length(s)), case1, result);
result = m().mk_ite(m_autil.mk_ge(k, str().mk_length(s)), case2, result);
result = m().mk_ite(m_autil.mk_lt(b, zero()), case3, result);
return BR_REWRITE_FULL;
}
}
expr* es[2] = { a, b};
expr* la = str().mk_length(a);
result = m().mk_ite(m().mk_and(m_autil.mk_ge(b, zero()), m().mk_not(m_autil.mk_le(la, b))),
m().mk_app(m_util.get_family_id(), OP_SEQ_NTH_I, 2, es),
m().mk_app(m_util.get_family_id(), OP_SEQ_NTH_U, 2, es));
str().mk_nth_i(a, b),
str().mk_nth_u(a, b));
return BR_REWRITE_FULL;
}

1
src/ast/seq_decl_plugin.h
View file

@ -286,6 +286,7 @@ public:
app* mk_at(expr* s, expr* i) const { expr* es[2] = { s, i }; return m.mk_app(m_fid, OP_SEQ_AT, 2, es); }
app* mk_nth(expr* s, expr* i) const { expr* es[2] = { s, i }; return m.mk_app(m_fid, OP_SEQ_NTH, 2, es); }
app* mk_nth_i(expr* s, expr* i) const { expr* es[2] = { s, i }; return m.mk_app(m_fid, OP_SEQ_NTH_I, 2, es); }
app* mk_nth_u(expr* s, expr* i) const { expr* es[2] = { s, i }; return m.mk_app(m_fid, OP_SEQ_NTH_U, 2, es); }
app* mk_nth_c(expr* s, unsigned i) const;
app* mk_substr(expr* a, expr* b, expr* c) const { expr* es[3] = { a, b, c }; return m.mk_app(m_fid, OP_SEQ_EXTRACT, 3, es); }