don't rewrite empty/non-empty checking predicates

Signed-off-by: Nikolaj Bjorner <[email protected]>

src/smt/seq_regex.cpp

@@ -411,8 +411,10 @@ namespace smt {
             << "," << expr_id_str(u) << "," << expr_id_str(n) << ") ";);
 
         expr_ref is_nullable = is_nullable_wrapper(r);
-        if (m.is_true(is_nullable))
+        if (m.is_true(is_nullable)) {
+            TRACE("seq_regex", tout << "is nullable\n";);
             return;
+        }
         literal null_lit = th.mk_literal(is_nullable);
         expr_ref hd = mk_first(r, n);
         expr_ref d(m);
@@ -433,12 +435,13 @@ namespace smt {
             rewrite(cond);
             if (m.is_false(cond))
                 continue;            
-            expr_ref next_non_empty = sk().mk_is_non_empty(p.second, re().mk_union(u, r), n);
+            expr_ref next_non_empty = sk().mk_is_non_empty(p.second, re().mk_union(u, p.second), n);
             if (!m.is_true(cond))
                 next_non_empty = m.mk_and(cond, next_non_empty);
             lits.push_back(th.mk_literal(next_non_empty));
         }
 
+        TRACE("seq_regex", tout << lits << "\n";);
         th.add_axiom(lits);
     }
 
@@ -518,7 +521,7 @@ namespace smt {
                 expr_ref ncond(mk_not(m, cond), m);
                 lits.push_back(th.mk_literal(mk_forall(m, hd, ncond)));
             }
-            expr_ref is_empty1 = sk().mk_is_empty(p.second, re().mk_union(u, r), n);    
+            expr_ref is_empty1 = sk().mk_is_empty(p.second, re().mk_union(u, p.second), n);    
             lits.push_back(th.mk_literal(is_empty1)); 
             th.add_axiom(lits);
         }        

src/smt/seq_skolem.cpp

@@ -40,14 +40,15 @@ seq_skolem::seq_skolem(ast_manager& m, th_rewriter& rw):
     m_is_non_empty   = "re.is_non_empty";
 }
 
-expr_ref seq_skolem::mk(symbol const& s, expr* e1, expr* e2, expr* e3, expr* e4, sort* range) {
+expr_ref seq_skolem::mk(symbol const& s, expr* e1, expr* e2, expr* e3, expr* e4, sort* range, bool rw) {
     expr* es[4] = { e1, e2, e3, e4 };
     unsigned len = e4?4:(e3?3:(e2?2:(e1?1:0)));
     if (!range) {
         range = m.get_sort(e1);
     }
     expr_ref result(seq.mk_skolem(s, len, es, range), m);
-    m_rewrite(result);
+    if (rw) 
+        m_rewrite(result);
     return result;
 }
 

src/smt/seq_skolem.h

@@ -48,8 +48,8 @@ namespace smt {
         expr_ref mk(symbol const& s, sort* range) { return mk(s, nullptr, nullptr, nullptr, nullptr, range); }
         expr_ref mk(symbol const& s, expr* e, sort* range) { return mk(s, e, nullptr, nullptr, nullptr, range); }
         expr_ref mk(symbol const& s, expr* e1, expr* e2, sort* range) { return mk(s, e1, e2, nullptr, nullptr, range); }
-        expr_ref mk(symbol const& s, expr* e1, expr* e2, expr* e3, sort* range) { return mk(s, e1, e2, e3, nullptr, range); }
-        expr_ref mk(symbol const& s, expr* e1, expr* e2 = nullptr, expr* e3 = nullptr, expr* e4 = nullptr, sort* range = nullptr);
+        expr_ref mk(symbol const& s, expr* e1, expr* e2, expr* e3, sort* range, bool rw = true) { return mk(s, e1, e2, e3, nullptr, range, rw); }
+        expr_ref mk(symbol const& s, expr* e1, expr* e2 = nullptr, expr* e3 = nullptr, expr* e4 = nullptr, sort* range = nullptr, bool rw = true);
 
         expr_ref mk(char const* s, sort* range) { return mk(s, nullptr, nullptr, nullptr, nullptr, range); }
         expr_ref mk(char const* s, expr* e, sort* range) { return mk(s, e, nullptr, nullptr, nullptr, range); }
@@ -72,8 +72,8 @@ namespace smt {
         }
         expr_ref mk_accept(expr_ref_vector const& args) { return expr_ref(seq.mk_skolem(m_accept, args.size(), args.c_ptr(), m.mk_bool_sort()), m); }
         expr_ref mk_accept(expr* s, expr* i, expr* r) { return mk(m_accept, s, i, r, nullptr, m.mk_bool_sort()); }
-        expr_ref mk_is_non_empty(expr* r, expr* u, expr* n) { return mk(m_is_non_empty, r, u, n, m.mk_bool_sort()); }
-        expr_ref mk_is_empty(expr* r, expr* u, expr* n) { return mk(m_is_empty, r, u, n, m.mk_bool_sort()); }
+        expr_ref mk_is_non_empty(expr* r, expr* u, expr* n) { return mk(m_is_non_empty, r, u, n, m.mk_bool_sort(), false); }
+        expr_ref mk_is_empty(expr* r, expr* u, expr* n) { return mk(m_is_empty, r, u, n, m.mk_bool_sort(), false); }
 
         expr_ref mk_indexof_left(expr* t, expr* s, expr* offset = nullptr) { return mk(m_indexof_left, t, s, offset); }
         expr_ref mk_indexof_right(expr* t, expr* s, expr* offset = nullptr) { return mk(m_indexof_right, t, s, offset); }