diff --git a/src/ast/rewriter/seq_rewriter.cpp b/src/ast/rewriter/seq_rewriter.cpp
index 442de5503..2b8689264 100644
--- a/src/ast/rewriter/seq_rewriter.cpp
+++ b/src/ast/rewriter/seq_rewriter.cpp
@@ -126,6 +126,16 @@ eautomaton* re2automaton::re2aut(expr* e) {
         }
         return b.detach();        
     }
+    else if (u.re.is_loop(e, e1, lo) && (a = re2aut(e1))) {
+        b = eautomaton::clone(*a);
+        b->add_final_to_init_moves();
+        b->add_init_to_final_states();        
+        while (lo > 0) {
+            b = eautomaton::mk_concat(*a, *b);
+            --lo;
+        }
+        return b.detach();        
+    }
     else if (u.re.is_empty(e)) {
         return alloc(eautomaton, sm);
     }
@@ -200,7 +210,7 @@ br_status seq_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * con
     case OP_RE_INTERSECT:
         return BR_FAILED;    
     case OP_RE_LOOP:
-        return BR_FAILED;    
+        return mk_re_loop(num_args, args, result);
     case OP_RE_EMPTY_SET:
         return BR_FAILED;    
     case OP_RE_FULL_SET:
@@ -296,10 +306,14 @@ br_status seq_rewriter::mk_seq_concat(expr* a, expr* b, expr_ref& result) {
         return BR_REWRITE2;
     }
     if (m_util.str.is_empty(a)) {
-        result = b;
+        result = a;
         return BR_DONE;
     }
     if (m_util.str.is_empty(b)) {
+        result = b;
+        return BR_DONE;
+    }
+    if (m_util.re.is_full(a) && m_util.re.is_full(b)) {
         result = a;
         return BR_DONE;
     }
@@ -690,14 +704,14 @@ br_status seq_rewriter::mk_str_stoi(expr* a, expr_ref& result) {
     return BR_FAILED;
 }
 
-void seq_rewriter::add_next(u_map<expr*>& next, unsigned idx, expr* cond) {
+void seq_rewriter::add_next(u_map<expr*>& next, expr_ref_vector& trail, unsigned idx, expr* cond) {
     expr* acc;
-    if (m().is_true(cond) || !next.find(idx, acc)) {              
-        next.insert(idx, cond);                   
-    }                                                   
-    else {                                              
-        next.insert(idx, m().mk_or(cond, acc));   
+    if (!m().is_true(cond) && next.find(idx, acc)) {              
+        cond = m().mk_or(cond, acc);
     }
+    trail.push_back(cond);
+    next.insert(idx, cond);   
+
 }
 
 bool seq_rewriter::is_sequence(eautomaton& aut, expr_ref_vector& seq) {
@@ -807,9 +821,10 @@ br_status seq_rewriter::mk_str_in_regexp(expr* a, expr* b, expr_ref& result) {
             aut->get_moves_from(state, mvs, false);
             for (unsigned j = 0; j < mvs.size(); ++j) {
                 eautomaton::move const& mv = mvs[j];
+				SASSERT(mv.t());
                 if (mv.t()->is_char() && m().is_value(mv.t()->get_char()) && m().is_value(ch)) {
                     if (mv.t()->get_char() == ch) {
-                        add_next(next, mv.dst(), acc);
+                        add_next(next, trail, mv.dst(), acc);
                     }
                     else {
                         continue;
@@ -818,7 +833,7 @@ br_status seq_rewriter::mk_str_in_regexp(expr* a, expr* b, expr_ref& result) {
                 else {
                     cond = mv.t()->accept(ch);
                     if (!m().is_true(acc)) cond = m().mk_and(acc, cond);
-                    add_next(next, mv.dst(), cond);
+                    add_next(next, trail, mv.dst(), cond);
                 }
             }                
         }
@@ -838,6 +853,7 @@ br_status seq_rewriter::mk_str_in_regexp(expr* a, expr* b, expr_ref& result) {
         }
     }
     result = mk_or(ors);
+    TRACE("seq", tout << result << "\n";);
     return BR_REWRITE_FULL;
 }
 br_status seq_rewriter::mk_str_to_regexp(expr* a, expr_ref& result) {
@@ -864,6 +880,22 @@ br_status seq_rewriter::mk_re_union(expr* a, expr* b, expr_ref& result) {
         result = a;
         return BR_DONE;
     }
+    if (m_util.re.is_empty(a)) {
+        result = b;
+        return BR_DONE;
+    }
+    if (m_util.re.is_empty(b)) {
+        result = a;
+        return BR_DONE;
+    }
+    if (m_util.re.is_full(a)) {
+        result = a;
+        return BR_DONE;
+    }
+    if (m_util.re.is_full(b)) {
+        result = b;
+        return BR_DONE;
+    }
     if (m_util.re.is_star(a) && is_epsilon(b)) {
         result = a;
         return BR_DONE;
@@ -874,6 +906,32 @@ br_status seq_rewriter::mk_re_union(expr* a, expr* b, expr_ref& result) {
     }
     return BR_FAILED;
 }
+
+
+br_status seq_rewriter::mk_re_loop(unsigned num_args, expr* const* args, expr_ref& result) {
+    rational n1, n2;
+    switch (num_args) {
+    case 1: 
+        break;
+    case 2:
+        if (m_autil.is_numeral(args[1], n1) && n1.is_unsigned()) {
+            result = m_util.re.mk_loop(args[0], n1.get_unsigned());
+            return BR_DONE;
+        }
+        break;
+    case 3:
+        if (m_autil.is_numeral(args[1], n1) && n1.is_unsigned() &&
+            m_autil.is_numeral(args[2], n2) && n2.is_unsigned()) {
+            result = m_util.re.mk_loop(args[0], n1.get_unsigned(), n2.get_unsigned());
+            return BR_DONE;
+        }
+        break;
+    default:
+        break;
+    }
+    return BR_FAILED;
+}
+
 /*
   a** = a*
   (a* + b)* = (a + b)*
@@ -882,7 +940,7 @@ br_status seq_rewriter::mk_re_union(expr* a, expr* b, expr_ref& result) {
 */
 br_status seq_rewriter::mk_re_star(expr* a, expr_ref& result) {
     expr* b, *c, *b1, *c1;
-    if (m_util.re.is_star(a)) {
+    if (m_util.re.is_star(a) || m_util.re.is_empty(a) || m_util.re.is_full(a)) {
         result = a;
         return BR_DONE;
     }
diff --git a/src/ast/rewriter/seq_rewriter.h b/src/ast/rewriter/seq_rewriter.h
index 77af42dee..f65b22b12 100644
--- a/src/ast/rewriter/seq_rewriter.h
+++ b/src/ast/rewriter/seq_rewriter.h
@@ -36,7 +36,7 @@ public:
     static sym_expr* mk_char(expr_ref& t) { return alloc(sym_expr, false, t); }
     static sym_expr* mk_char(ast_manager& m, expr* t) { expr_ref tr(t, m); return alloc(sym_expr, false, tr); }
     static sym_expr* mk_pred(expr_ref& t) { return alloc(sym_expr, true, t); }
-    void inc_ref() { ++m_ref; }
+    void inc_ref() { ++m_ref;  }
     void dec_ref() { --m_ref; if (m_ref == 0) dealloc(this); }
     std::ostream& display(std::ostream& out) const;
     bool is_char() const { return !m_is_pred; }
@@ -91,6 +91,7 @@ class seq_rewriter {
     br_status mk_re_star(expr* a, expr_ref& result);
     br_status mk_re_plus(expr* a, expr_ref& result);
     br_status mk_re_opt(expr* a, expr_ref& result);
+    br_status mk_re_loop(unsigned num_args, expr* const* args, expr_ref& result);
 
     bool set_empty(unsigned sz, expr* const* es, bool all, expr_ref_vector& lhs, expr_ref_vector& rhs);
     bool is_subsequence(unsigned n, expr* const* l, unsigned m, expr* const* r, 
@@ -100,7 +101,7 @@ class seq_rewriter {
     bool min_length(unsigned n, expr* const* es, unsigned& len);
     expr* concat_non_empty(unsigned n, expr* const* es);
 
-    void add_next(u_map<expr*>& next, unsigned idx, expr* cond);
+    void add_next(u_map<expr*>& next, expr_ref_vector& trail, unsigned idx, expr* cond);
     bool is_sequence(expr* e, expr_ref_vector& seq);
     bool is_sequence(eautomaton& aut, expr_ref_vector& seq);
     bool is_epsilon(expr* e) const;
diff --git a/src/ast/seq_decl_plugin.cpp b/src/ast/seq_decl_plugin.cpp
index 393556b58..5bbc26e6d 100644
--- a/src/ast/seq_decl_plugin.cpp
+++ b/src/ast/seq_decl_plugin.cpp
@@ -163,9 +163,6 @@ std::string zstring::encode() const {
         unsigned char ch = m_buffer[i];
         if (0 <= ch && ch < 32) {
             strm << esc_table[ch];
-        }        
-        else if (ch == 127) {
-            strm << "^?";
         }
         else {
             strm << (char)(ch);
@@ -248,13 +245,15 @@ seq_decl_plugin::seq_decl_plugin(): m_init(false),
                                     m_stringc_sym("String"),
                                     m_charc_sym("Char"),
                                     m_string(0),
-                                    m_char(0) {}
+                                    m_char(0),
+                                    m_re(0) {}
 
 void seq_decl_plugin::finalize() {
     for (unsigned i = 0; i < m_sigs.size(); ++i) 
         dealloc(m_sigs[i]);
     m_manager->dec_ref(m_string);
     m_manager->dec_ref(m_char);
+    m_manager->dec_ref(m_re);
 }
 
 bool seq_decl_plugin::is_sort_param(sort* s, unsigned& idx) {
@@ -479,6 +478,9 @@ void seq_decl_plugin::set_manager(ast_manager* m, family_id id) {
     parameter param(m_char);
     m_string = m->mk_sort(symbol("String"), sort_info(m_family_id, SEQ_SORT, 1, &param));
     m->inc_ref(m_string);
+    parameter paramS(m_string);
+    m_re = m->mk_sort(m_family_id, RE_SORT, 1, &paramS);
+    m->inc_ref(m_re);
 }
 
 sort * seq_decl_plugin::mk_sort(decl_kind k, unsigned num_parameters, parameter const * parameters) {
@@ -567,20 +569,40 @@ func_decl * seq_decl_plugin::mk_func_decl(decl_kind k, unsigned num_parameters,
         return m.mk_func_decl(m_sigs[k]->m_name, arity, domain, rng, func_decl_info(m_family_id, k));
 
     case _OP_REGEXP_FULL:
+        if (!range) {
+            range = m_re;
+        }
         match(*m_sigs[k], arity, domain, range, rng);
         return m.mk_func_decl(symbol("re.allchar"), arity, domain, rng, func_decl_info(m_family_id, OP_RE_FULL_SET));
     case _OP_REGEXP_EMPTY:
+        if (!range) {
+            range = m_re;
+        }
         match(*m_sigs[k], arity, domain, range, rng);
         return m.mk_func_decl(symbol("re.nostr"), arity, domain, rng, func_decl_info(m_family_id, OP_RE_EMPTY_SET));
         
     case OP_RE_LOOP:
-        match(*m_sigs[k], arity, domain, range, rng);
-        if (num_parameters != 2 || !parameters[0].is_int() || !parameters[1].is_int()) {
-            m.raise_exception("Expecting two numeral parameters to function re-loop");
+        switch (arity) {
+        case 1:
+            match(*m_sigs[k], arity, domain, range, rng);
+            if (num_parameters == 0 || num_parameters > 2 || !parameters[0].is_int() || (num_parameters == 2 && !parameters[1].is_int())) {
+                m.raise_exception("Expecting two numeral parameters to function re-loop");
+            }
+            return m.mk_func_decl(m_sigs[k]->m_name, arity, domain, rng, func_decl_info(m_family_id, k, num_parameters, parameters));   
+        case 2:
+            if (m_re != domain[0] || !arith_util(m).is_int(domain[1])) {
+                m.raise_exception("Incorrect type of arguments passed to re.loop. Expecting regular expression and two integer parameters");
+            }
+            return m.mk_func_decl(m_sigs[k]->m_name, arity, domain, domain[0], func_decl_info(m_family_id, k, num_parameters, parameters));
+        case 3:
+            if (m_re != domain[0] || !arith_util(m).is_int(domain[1]) || !arith_util(m).is_int(domain[2])) {
+                m.raise_exception("Incorrect type of arguments passed to re.loop. Expecting regular expression and two integer parameters");
+            }
+            return m.mk_func_decl(m_sigs[k]->m_name, arity, domain, domain[0], func_decl_info(m_family_id, k, num_parameters, parameters));
+        default:
+            m.raise_exception("Incorrect number of arguments passed to loop. Expected 1 regular expression and two integer parameters");            
         }
-        return m.mk_func_decl(m_sigs[k]->m_name, arity, domain, rng, func_decl_info(m_family_id, k, num_parameters, parameters));   
-
-
+        
 
     case OP_STRING_CONST:
         if (!(num_parameters == 1 && arity == 0 && parameters[0].is_symbol())) {
@@ -768,17 +790,37 @@ void seq_util::str::get_concat(expr* e, expr_ref_vector& es) const {
     }
 }
 
+app* seq_util::re::mk_loop(expr* r, unsigned lo) {
+    parameter param(lo);
+    return m.mk_app(m_fid, OP_RE_LOOP, 1, &param, 1, &r);
+}
+
+app* seq_util::re::mk_loop(expr* r, unsigned lo, unsigned hi) {
+    parameter params[2] = { parameter(lo), parameter(hi) };
+    return m.mk_app(m_fid, OP_RE_LOOP, 2, params, 1, &r);
+}
+
 bool seq_util::re::is_loop(expr const* n, expr*& body, unsigned& lo, unsigned& hi)  {
     if (is_loop(n)) {
         app const* a = to_app(n);
-        SASSERT(a->get_num_args() == 1);
-        SASSERT(a->get_decl()->get_num_parameters() == 2);
-        body = a->get_arg(0);
-        lo = a->get_decl()->get_parameter(0).get_int();
-        hi = a->get_decl()->get_parameter(1).get_int();
-        return true;
-    }
-    else {
-        return false;
+        if (a->get_num_args() == 1 && a->get_decl()->get_num_parameters() == 2) {
+            body = a->get_arg(0);
+            lo = a->get_decl()->get_parameter(0).get_int();
+            hi = a->get_decl()->get_parameter(1).get_int();
+            return true;
+        }
     }
+    return false;    
+}
+
+bool seq_util::re::is_loop(expr const* n, expr*& body, unsigned& lo)  {
+    if (is_loop(n)) {
+        app const* a = to_app(n);
+        if (a->get_num_args() == 1 && a->get_decl()->get_num_parameters() == 1) {
+            body = a->get_arg(0);
+            lo = a->get_decl()->get_parameter(0).get_int();
+            return true;
+        }
+    }
+    return false;    
 }
diff --git a/src/ast/seq_decl_plugin.h b/src/ast/seq_decl_plugin.h
index ecb118581..611020a69 100644
--- a/src/ast/seq_decl_plugin.h
+++ b/src/ast/seq_decl_plugin.h
@@ -136,6 +136,7 @@ class seq_decl_plugin : public decl_plugin {
     symbol           m_charc_sym;
     sort*            m_string;
     sort*            m_char;
+    sort*            m_re;
 
     void match(psig& sig, unsigned dsz, sort* const* dom, sort* range, sort_ref& rng);
 
@@ -297,6 +298,8 @@ public:
         app* mk_star(expr* r) { return m.mk_app(m_fid, OP_RE_STAR, r); }
         app* mk_plus(expr* r) { return m.mk_app(m_fid, OP_RE_PLUS, r); }
         app* mk_opt(expr* r) { return m.mk_app(m_fid, OP_RE_OPTION, r); }        
+        app* mk_loop(expr* r, unsigned lo);
+        app* mk_loop(expr* r, unsigned lo, unsigned hi);
 
         bool is_to_re(expr const* n)    const { return is_app_of(n, m_fid, OP_SEQ_TO_RE); }
         bool is_concat(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_CONCAT); }
@@ -318,7 +321,7 @@ public:
         MATCH_UNARY(is_plus);
         MATCH_UNARY(is_opt);
         bool is_loop(expr const* n, expr*& body, unsigned& lo, unsigned& hi);
-        
+        bool is_loop(expr const* n, expr*& body, unsigned& lo);        
     };
     str str;
     re  re;
diff --git a/src/smt/theory_seq.cpp b/src/smt/theory_seq.cpp
index 185e92ea2..4ac7e8f7e 100644
--- a/src/smt/theory_seq.cpp
+++ b/src/smt/theory_seq.cpp
@@ -585,7 +585,7 @@ void theory_seq::propagate_lit(dependency* dep, unsigned n, literal const* _lits
     enode_pair_vector eqs;
     linearize(dep, eqs, lits);
     TRACE("seq", ctx.display_detailed_literal(tout, lit); 
-          tout << " <- "; ctx.display_literals_verbose(tout, lits.size(), lits.c_ptr()); display_deps(tout, dep);); 
+          tout << " <- "; ctx.display_literals_verbose(tout, lits.size(), lits.c_ptr()); if (!lits.empty()) tout << "\n"; display_deps(tout, dep);); 
     justification* js = 
         ctx.mk_justification(
             ext_theory_propagation_justification(
@@ -600,7 +600,7 @@ void theory_seq::set_conflict(dependency* dep, literal_vector const& _lits) {
     enode_pair_vector eqs;
     literal_vector lits(_lits);
     linearize(dep, eqs, lits);
-    TRACE("seq", ctx.display_literals_verbose(tout, lits.size(), lits.c_ptr()); display_deps(tout, dep); ;); 
+    TRACE("seq", ctx.display_literals_verbose(tout, lits.size(), lits.c_ptr()); if (!lits.empty()) tout << "\n"; display_deps(tout, dep); ;); 
     m_new_propagation = true;
     ctx.set_conflict(
         ctx.mk_justification(
@@ -617,7 +617,7 @@ void theory_seq::propagate_eq(dependency* dep, enode* n1, enode* n2) {
     enode_pair_vector eqs;
     linearize(dep, eqs, lits);
     TRACE("seq",
-          tout << mk_pp(n1->get_owner(), m) << " = " << mk_pp(n2->get_owner(), m) << " <- ";
+          tout << mk_pp(n1->get_owner(), m) << " = " << mk_pp(n2->get_owner(), m) << " <- \n";
           display_deps(tout, dep);
           ); 
     
@@ -987,6 +987,10 @@ bool theory_seq::solve_ne(unsigned idx) {
         }
         else if (!change) {
             TRACE("seq", tout << "no change " << n.ls(i) << " " << n.rs(i) << "\n";);
+            if (updated) {
+                new_ls.push_back(n.ls(i));
+                new_rs.push_back(n.rs(i));
+            }
             continue;
         }
         else {
@@ -1197,7 +1201,7 @@ void theory_seq::display(std::ostream & out) const {
 void theory_seq::display_equations(std::ostream& out) const {
     for (unsigned i = 0; i < m_eqs.size(); ++i) {
         eq const& e = m_eqs[i];
-        out << e.ls() << " = " << e.rs() << " <- ";
+        out << e.ls() << " = " << e.rs() << " <- \n";
         display_deps(out, e.dep());
     }       
 }
@@ -1231,13 +1235,13 @@ void theory_seq::display_deps(std::ostream& out, dependency* dep) const {
     enode_pair_vector eqs;
     linearize(dep, eqs, lits);
     for (unsigned i = 0; i < eqs.size(); ++i) {
-        out << "\n   " << mk_pp(eqs[i].first->get_owner(), m) << " = " << mk_pp(eqs[i].second->get_owner(), m);
+        out << "   " << mk_pp(eqs[i].first->get_owner(), m) << " = " << mk_pp(eqs[i].second->get_owner(), m) << "\n";
     }
     for (unsigned i = 0; i < lits.size(); ++i) {
         literal lit = lits[i];
-        get_context().display_literals_verbose(out << "\n   ", 1, &lit);
+        get_context().display_literals_verbose(out << "   ", 1, &lit);
+        tout << "\n";
     }
-    out << "\n";        
 }
 
 void theory_seq::collect_statistics(::statistics & st) const {
@@ -2204,6 +2208,7 @@ void theory_seq::new_diseq_eh(theory_var v1, theory_var v2) {
     expr_ref eq(m.mk_eq(e1, e2), m);
     m_rewrite(eq);
     if (!m.is_false(eq)) {
+        TRACE("seq", tout << "new disequality: " << eq << "\n";);
         literal lit = ~mk_eq(e1, e2, false);
         //SASSERT(get_context().get_assignment(lit) == l_true);
         dependency* dep = m_dm.mk_leaf(assumption(lit));