Implements the algorithm of Eq(p,q) = Empty(p XOR q)' using a union-find
driven bisimulation closure (per the CAV'26 ERE paper).
### What's added
* **New primitive OP_RE_XOR (re.xor)** wired through seq_decl_plugin:
parser signature, info propagation (nullable, min_length), and
pretty-printer.
* **seq_rewriter**: structural XOR rewrites ( XOR r = empty, XOR empty =
r, ull XOR r = comp(r), comp/comp absorption, complement push, AC
normalisation), nullability (Null(p XOR q) = Null(p) != Null(q)),
derivative (D_a(p XOR q) = D_a(p) XOR D_a(q)), reverse, antimirov
derivative, and `check_deriv_normal_form` coverage.
* **New class seq::regex_bisim** in
`src/ast/rewriter/seq_regex_bisim.{h,cpp}` to keep the bisim logic out
of the already-large `seq_rewriter.cpp`. Uses `basic_union_find` from
`util/union_find.h`, an `obj_map` for the node assignment, and a
50000-step bound (returns `l_undef` on overrun).
* **Integration** in `seq_rewriter::reduce_re_eq` (with a re-entry
guard) and in `seq_regex::propagate_eq` / `propagate_ne` for ground
regexes; on `l_undef` we fall back to the existing axiomatisation.
* **`sls_seq_plugin`**: extend `OP_RE_DIFF` switch arms to also cover
`OP_RE_XOR`.
### Validation
* Full release build with MSVC + Ninja.
* `./test-z3 /a` -- 89/89 tests passing.
* `./test-z3 /seq smt2print_parse` -- PASS.
* Smoke tests with `(a|b)*` vs `(a*b*)*` (equal) and `a*` vs `(a|b)*`
(not equal) return the expected `sat`/`unsat` quickly.
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
`seq_plugin::edit_distance_with_updates` used the left-string DP index
when checking whether the right string could accept an insertion from
the `d[i][j - 1]` transition. This miscomputed updateable edit distance
and could suppress valid repair proposals when `i != j`.
- **Bug fix**
- Change the right-side insertion guard in
`src/ast/sls/sls_seq_plugin.cpp` from `b.can_add(i - 1)` to `b.can_add(j
- 1)`.
- This aligns the mutability check with the DP transition being
evaluated and with the existing update-generation logic below it.
- **Regression coverage**
- Add a focused test in `src/test/sls_seq_plugin.cpp` for an asymmetric
variable/value layout on the right-hand side.
- The test asserts that the repair logic admits the right-side add at `j
- 1`, which is the case that the previous index mixup could reject.
- **Reference**
- The updated condition now matches the intended transition semantics:
```cpp
if (d[i][j - 1] < u[i][j] && b.can_add(j - 1)) {
m_string_updates.reset();
u[i][j] = d[i][j - 1];
}
```
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
`src/ast/sls/sls_seq_plugin.cpp::is_sat()` had two unconditional abort
paths (`VERIFY(false)` and `NOT_IMPLEMENTED_YET()`) reachable from valid
string formulas under SLS. This changes those paths to graceful
repair/fail behavior so SLS can continue search instead of terminating
the process.
- **Length coherence fallback no longer aborts**
- Replaced the terminal `VERIFY(false)` in the `str.len` coherence block
with a normal `return false` repair failure path.
- Effect: failed local repair is propagated to the outer SLS loop
instead of crashing.
- **Implemented `seq.last_indexof` coherence handling**
- Replaced `NOT_IMPLEMENTED_YET()` with concrete coherence logic:
- read current `x`, `y`, and `e`,
- compute `actual = sx.last_indexof(sy)`,
- update `e` when `e != actual`,
- otherwise continue.
- Effect: formulas containing `seq.last_indexof` are handled in SLS
coherence checks instead of aborting.
- **No new hard-abort behavior introduced**
- In the new `last_index` block, non-numeral `e` is handled by graceful
`return false` (repair failure), not assertion abort.
```cpp
if (seq.str.is_last_index(e, x, y) && seq.is_string(x->get_sort())) {
auto sx = strval0(x), sy = strval0(y);
rational val_e;
if (!a.is_numeral(ctx.get_value(e), val_e))
return false;
rational actual(sx.last_indexof(sy));
if (val_e == actual) continue;
update(e, actual);
return false;
}
```
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
`add_substr_edit_updates` uses a `HashSet` to deduplicate substrings of
`val_other`, but on a duplicate hit it `break`s the inner loop instead
of skipping just that entry. This causes all longer substrings from the
same starting position to be silently dropped as repair candidates.
## Change
- **`src/ast/sls/sls_seq_plugin.cpp`** — replace `break` with `continue`
in the inner substring-enumeration loop.
```cpp
// Before — exits the inner loop on first duplicate, missing e.g. "ab" in "aab"
if (set.contains(sub))
break;
// After — skips only the duplicate, continues with longer substrings at same offset
if (set.contains(sub))
continue;
```
For `val_other = "aab"`, the old code never proposed `"ab"` (i=1, j=2)
as a repair candidate because the duplicate `"a"` (i=1, j=1) terminated
the inner loop prematurely.
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
* Initial plan
* Update z3 codebase to use std::string_view (except z3++.h)
- Updated params.cpp/h to use string_view internally for parameter descriptions
- Updated trace.h/cpp to accept string_view for trace tag functions
- Updated hash.h/cpp to use string_view for string_hash function
- Updated all callers of string_hash to use string_view
- Properly handled nullptr to empty string_view conversions
- All tests passing
Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>
* Add missing string_view includes to headers
Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>
- i is the offset into val_other. The valid offsets are 0... |val_other|-1.
- j is the length of the substring. It only makes sense to extract strings of length 1,... |val_other|-i
* Fixed range regex
* Fix sls for str.at
* Added case for str.at
* Pad/Truncate string in sls extract/length to fit length constraints
* Guarded index check
* Added missing progressing cases in extraction
* Add padding if required
* Commented out debug output
* Fixed spurious counterexamples in seq-sls. Updates might not be identity mapping
* Removed debug code
* One check was missing
* Trying different update generation function
* Renamed function
* Added parameter to select string update function
