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fix rewriting of complemnt of ranges

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2026-06-20 11:07:52 -07:00
parent 881360db5a
commit 871b98169f
3 changed files with 30 additions and 26 deletions
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20
src/ast/rewriter/seq_rewriter.cpp
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@ -4832,26 +4832,32 @@ br_status seq_rewriter::mk_re_complement(expr* a, expr_ref& result) {
sort* srt = a->get_sort();
bool has_left = (lo_v > 0);
bool has_right = (hi_v < max_c);
auto empty_re = [&]() { return re().mk_empty(srt); };
auto full_re = [&]() { return re().mk_full_seq(srt); };
if (!has_left && !has_right) {
// [0, max_c]: complement is empty
result = re().mk_empty(srt);
result = empty_re();
return BR_DONE;
}
if (lo_v > hi_v) {
result = full_re();
return BR_DONE;
}
if (!has_left) {
// [0, b]: complement is [b+1, max]
result = re().mk_range(srt, hi_v + 1, max_c);
return BR_REWRITE1;
result = re().mk_union(empty_re(), re().mk_concat(re().mk_range(srt, hi_v + 1, max_c), full_re()));
return BR_DONE;
}
if (!has_right) {
// [a, max]: complement is [0, a-1]
result = re().mk_range(srt, 0u, lo_v - 1);
return BR_REWRITE1;
result = re().mk_union(empty_re(), re().mk_concat(re().mk_range(srt, 0u, lo_v - 1), full_re()));
return BR_DONE;
}
// General: [a, b] → [0, a-1] ∪ [b+1, max]
auto left = re().mk_range(srt, 0u, lo_v - 1);
auto right = re().mk_range(srt, hi_v + 1, max_c);
result = re().mk_union(left, right);
return BR_REWRITE1;
result = re().mk_union(empty_re(), re().mk_concat(re().mk_union(left, right), full_re()));
return BR_DONE;
}
return BR_FAILED;
}