diff --git a/scripts/mk_project.py b/scripts/mk_project.py
index eb7218d4b..08986d96b 100644
--- a/scripts/mk_project.py
+++ b/scripts/mk_project.py
@@ -16,11 +16,12 @@ def init_project_def():
     add_lib('nlsat', ['polynomial', 'sat'])
     add_lib('hilbert', ['util'], 'math/hilbert')
     add_lib('simplex', ['util'], 'math/simplex')
+    add_lib('automata', ['util'], 'math/automata')
     add_lib('interval', ['util'], 'math/interval')
     add_lib('realclosure', ['interval'], 'math/realclosure')
     add_lib('subpaving', ['interval'], 'math/subpaving')
     add_lib('ast', ['util', 'polynomial'])
-    add_lib('rewriter', ['ast', 'polynomial'], 'ast/rewriter')
+    add_lib('rewriter', ['ast', 'polynomial', 'automata'], 'ast/rewriter')
     add_lib('normal_forms', ['rewriter'], 'ast/normal_forms')
     add_lib('model', ['rewriter'])
     add_lib('tactic', ['ast', 'model'])
diff --git a/src/ast/rewriter/seq_rewriter.cpp b/src/ast/rewriter/seq_rewriter.cpp
index d7ac3ff67..41c20f599 100644
--- a/src/ast/rewriter/seq_rewriter.cpp
+++ b/src/ast/rewriter/seq_rewriter.cpp
@@ -22,6 +22,7 @@ Notes:
 #include"ast_pp.h"
 #include"ast_util.h"
 #include"uint_set.h"
+#include"automaton.h"
 
 
 br_status seq_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * const * args, expr_ref & result) {
@@ -30,22 +31,38 @@ br_status seq_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * con
     switch(f->get_decl_kind()) {
 
     case OP_SEQ_UNIT:
-    case OP_SEQ_EMPTY:
-
-    case OP_RE_PLUS:
-    case OP_RE_STAR:
-    case OP_RE_OPTION:
-    case OP_RE_RANGE:
-    case OP_RE_CONCAT:
-    case OP_RE_UNION:
-    case OP_RE_INTERSECT:
-    case OP_RE_LOOP:
-    case OP_RE_EMPTY_SET:
-    case OP_RE_FULL_SET:
-    case OP_RE_OF_PRED:
-    case _OP_SEQ_SKOLEM:
         return BR_FAILED;
-    
+    case OP_SEQ_EMPTY:
+        return BR_FAILED;
+    case OP_RE_PLUS:
+        SASSERT(num_args == 1);
+        return mk_re_plus(args[0], result);
+    case OP_RE_STAR:
+        SASSERT(num_args == 1);
+        return mk_re_star(args[0], result);
+    case OP_RE_OPTION:
+        SASSERT(num_args == 1);
+        return mk_re_opt(args[0], result);
+    case OP_RE_CONCAT:
+        SASSERT(num_args == 2);
+        return mk_re_concat(args[0], args[1], result);
+    case OP_RE_UNION:
+        SASSERT(num_args == 2);
+        return mk_re_union(args[0], args[1], result);
+    case OP_RE_RANGE:
+        return BR_FAILED;    
+    case OP_RE_INTERSECT:
+        return BR_FAILED;    
+    case OP_RE_LOOP:
+        return BR_FAILED;    
+    case OP_RE_EMPTY_SET:
+        return BR_FAILED;    
+    case OP_RE_FULL_SET:
+        return BR_FAILED;    
+    case OP_RE_OF_PRED:
+        return BR_FAILED;    
+    case _OP_SEQ_SKOLEM:
+        return BR_FAILED;    
     case OP_SEQ_CONCAT: 
         if (num_args == 1) {
             result = args[0];
@@ -83,10 +100,11 @@ br_status seq_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * con
         SASSERT(num_args == 3);
         return mk_seq_replace(args[0], args[1], args[2], result);
     case OP_SEQ_TO_RE:
-        return BR_FAILED;
+        SASSERT(num_args == 1);
+        return mk_str_to_regexp(args[0], result);
     case OP_SEQ_IN_RE:
-        return BR_FAILED;
-
+        SASSERT(num_args == 2);
+        return mk_str_in_regexp(args[0], args[1], result);
     case OP_STRING_CONST:
         return BR_FAILED;
     case OP_STRING_ITOS: 
@@ -499,7 +517,10 @@ br_status seq_rewriter::mk_re_plus(expr* a, expr_ref& result) {
     return BR_FAILED;
 }
 br_status seq_rewriter::mk_re_opt(expr* a, expr_ref& result) {
-    return BR_FAILED;
+    sort* s;
+    VERIFY(m_util.is_re(a, s));
+    result = m_util.re.mk_union(m_util.re.mk_to_re(m_util.str.mk_empty(s)), a);
+    return BR_REWRITE1;
 }
 
 br_status seq_rewriter::mk_eq_core(expr * l, expr * r, expr_ref & result) {
diff --git a/src/ast/seq_decl_plugin.cpp b/src/ast/seq_decl_plugin.cpp
index 5b5ed1c55..10e9c00a5 100644
--- a/src/ast/seq_decl_plugin.cpp
+++ b/src/ast/seq_decl_plugin.cpp
@@ -629,6 +629,11 @@ app*  seq_util::str::mk_char(zstring const& s, unsigned idx) {
     return bvu.mk_numeral(s[idx], s.num_bits());
 }
 
+app*  seq_util::str::mk_char(char ch) {
+    zstring s(ch, zstring::ascii);
+    return mk_char(s, 0);
+}
+    
 bool seq_util::str::is_char(expr* n, zstring& c) const {
     if (u.is_char(n)) {
         c = zstring(to_app(n)->get_decl()->get_parameter(0).get_symbol().bare_str());
diff --git a/src/math/automata/automaton.cpp b/src/math/automata/automaton.cpp
new file mode 100644
index 000000000..ab908525e
--- /dev/null
+++ b/src/math/automata/automaton.cpp
@@ -0,0 +1,23 @@
+/*++
+Copyright (c) 2015 Microsoft Corporation
+
+Module Name:
+
+    automaton.cpp
+
+Abstract:
+
+    Symbolic Automaton, a la Margus Veanes Automata library.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2015-12-23.
+
+Revision History:
+
+
+--*/
+
+#include "automaton.h"
+
+template class automaton<unsigned>;
diff --git a/src/math/automata/automaton.h b/src/math/automata/automaton.h
new file mode 100644
index 000000000..e28db8fa0
--- /dev/null
+++ b/src/math/automata/automaton.h
@@ -0,0 +1,295 @@
+/*++
+Copyright (c) 2015 Microsoft Corporation
+
+Module Name:
+
+    automaton.h
+
+Abstract:
+
+    Symbolic Automaton, a la Margus Veanes Automata library.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2015-12-23.
+
+Revision History:
+
+
+--*/
+
+#ifndef AUTOMATON_H_
+#define AUTOMATON_H_
+
+
+#include "util.h"
+#include "vector.h"
+#include "uint_set.h"
+
+template<class T>
+class automaton {
+    class move {
+        T*       m_t;
+        unsigned m_src;
+        unsigned m_dst;        
+    public:
+        move(unsigned s, unsigned d, T* t = 0): m_t(t), m_src(s), m_dst(d) {}
+
+        unsigned dst() const { return m_dst; }
+        unsigned src() const { return m_src; }
+        T* t() const { return m_t; }
+
+        bool is_epsilon() const { return m_t == 0; }
+    };
+    typedef svector<move> moves;
+
+
+    svector<moves>  m_delta;
+    svector<moves>  m_delta_inv;
+    unsigned        m_init;
+    uint_set        m_final_set;
+    unsigned_vector m_final_states;
+    bool            m_is_epsilon_free;
+    bool            m_is_deterministic;
+    
+
+    // local data-structures
+    mutable uint_set        m_visited;
+    mutable unsigned_vector m_todo;
+
+
+public:
+
+    // The empty automaton:
+    automaton():
+        m_init(0),
+        m_is_epsilon_free(true),
+        m_is_deterministic(true)
+    {
+        m_delta.push_back(moves());
+        m_delta_inv.push_back(moves());
+    }
+
+
+    // create an automaton from initial state, final states, and moves
+    automaton(unsigned init, unsigned_vector const& final, moves const& mvs) {
+        m_is_epsilon_free = true;
+        m_is_deterministic = true;
+        m_init = init;
+        for (unsigned i = 0; i < final.size(); ++i) {
+            m_final_states.push_back(final[i]);
+            m_final_set.insert(final[i]);
+        }
+        for (unsigned i = 0; i < mvs.size(); ++i) {
+            move const& mv = mvs[i];
+            unsigned n = std::max(mv.src(), mv.dst());
+            if (n >= m_delta.size()) {
+                m_delta.resize(n+1, moves());
+                m_delta_inv.resize(n+1, moves());
+            }
+            m_delta[mv.src()].push_back(mv);
+            m_delta_inv[mv.dst()].push_back(mv);
+            m_is_deterministic &= m_delta[mv.src()].size() < 2;
+            m_is_epsilon_free &= !mv.is_epsilon();
+        }
+    }
+
+    // The automaton with a single state that is also final.
+    automaton(T* t, unsigned s = 0):
+        m_init(s) {
+        m_delta.resize(s+1, moves());
+        m_delta_inv.resize(s+1, moves());
+        m_final_set.insert(s);
+        m_final_states.push_back(s);
+        m_delta[s].push_back(move(s, s, t));
+        m_delta_inv[s].push_back(move(s, s, t));
+    }    
+
+    automaton(automaton const& other):
+        m_delta(other.m_delta),
+        m_delta_inv(other.m_delta_inv),        
+        m_init(other.m_init),
+        m_final_set(other.m_final_set),
+        m_final_states(other.m_final_states),
+        m_is_epsilon_free(other.m_is_epsilon_free),
+        m_is_deterministic(other.m_is_deterministic)
+    {}
+
+    // create the automaton that accepts the empty string only.
+    static automaton mk_epsilon() {
+        moves mvs;
+        unsigned_vector final;
+        final.push_back(0);        
+        return automaton(0, final, mvs);
+    }
+
+    // create the automaton with a single state on condition t.
+    static automaton mk_loop(T* t) {
+        moves mvs;
+        unsigned_vector final;
+        final.push_back(0);       
+        mvs.push_back(move(0, 0, t));
+        return automaton(0, final, mvs);
+    }
+
+    // create the sum of disjoint automata
+    static automaton mk_union(automaton const& a, automaton const& b) {
+        moves mvs;
+        unsigned_vector final;
+        unsigned offset1 = 1;
+        unsigned offset2 = a.num_states() + 1;
+        mvs.push_back(move(0, a.init() + offset1, 0));
+        mvs.push_back(move(0, b.init() + offset2, 0));
+        append_moves(offset1, a, mvs);
+        append_moves(offset2, b, mvs);
+        append_final(offset1, a, final);
+        append_final(offset2, b, final);
+        return automaton(0, final, mvs);
+    }
+
+    static automaton mk_reverse(automaton const& a) {
+        if (a.is_empty()) {
+            return automaton();
+        }
+        moves mvs;
+        for (unsigned i = 0; i < a.m_delta.size(); ++i) {
+            moves const& mvs1 = a.m_delta[i];
+            for (unsigned j = 0; j < mvs1.size(); ++j) {
+                move const& mv = mvs1[j];
+                mvs.push_back(move(mv.dst(), mv.src(), mv.t()));
+            }
+        }
+        unsigned_vector final;
+        unsigned init;
+        final.push_back(a.init());
+        if (a.m_final_states.size() == 1) {
+            init = a.m_final_states[0];
+        }
+        else {
+            init = a.num_states();
+            for (unsigned i = 0; i < a.m_final_states.size(); ++i) {
+                mvs.push_back(move(init, a.m_final_states[i]));
+            }
+        }
+        return automaton(init, final, mvs);        
+    }
+    
+    bool is_sequence(unsigned& length) const {
+        if (is_final_state(m_init) && (out_degree(m_init) == 0 || (out_degree(m_init) == 1 && is_loop_state(m_init)))) {
+            length = 0;
+            return true;
+        }
+        if (is_empty() || in_degree(m_init) != 0 || out_degree(m_init) != 1) {
+            return false;
+        }
+        
+        length = 1;
+        unsigned s = get_move_from(m_init).dst();
+        while (!is_final_state(s)) {  
+            if (out_degree(s) != 1 || in_degree(s) != 1) {
+                return false;
+            }
+            s = get_move_from(s).dst();
+            ++length;
+        }
+        return out_degree(s) == 0 || (out_degree(s) == 1 && is_loop_state(s));
+    }
+
+    unsigned init() const { return m_init; }
+    unsigned in_degree(unsigned state) const { return m_delta_inv[state].size(); }
+    unsigned out_degree(unsigned state) const { return m_delta[state].size(); }
+    move const& get_move_from(unsigned state) const { SASSERT(m_delta[state].size() == 1); return m_delta[state][0]; }
+    move const& get_move_to(unsigned state) const { SASSERT(m_delta_inv[state].size() == 1); return m_delta_inv[state][0]; }
+    moves const& get_moves_from(unsigned state) const { return m_delta[state]; }
+    moves const& get_moves_to(unsigned state) const { return m_delta_inv[state]; }
+    bool initial_state_is_source() const { return m_delta_inv[m_init].empty(); }
+    bool is_final_state(unsigned s) const { return m_final_set.contains(s); }
+    bool is_epsilon_free() const { return m_is_epsilon_free; }
+    bool is_deterministic() const { return m_is_deterministic; }
+    bool is_empty() const { return m_final_states.empty(); }
+    unsigned final_state() const { return m_final_states[0]; }
+    bool has_single_final_sink() const { return m_final_states.size() == 1 && m_delta[final_state()].empty(); }
+    unsigned num_states() const { return m_delta.size(); }
+    bool is_loop_state(unsigned s) const {
+        moves mvs;
+        get_moves_from(s, mvs);
+        for (unsigned i = 0; i < mvs.size(); ++i) {
+            if (s == mvs[i].dst()) return true;
+        }
+        return false;
+    }
+
+    unsigned move_count() const {
+        unsigned result = 0;
+        for (unsigned i = 0; i < m_delta.size(); result += m_delta[i].size(), ++i) {}
+        return result;
+    }
+    void get_epsilon_closure(unsigned state, unsigned_vector& states) {
+        get_epsilon_closure(state, m_delta, states);
+    }
+    void get_inv_epsilon_closure(unsigned state, unsigned_vector& states) {
+        get_epsilon_closure(state, m_delta_inv, states);
+    }
+    void get_moves_from(unsigned state, moves& mvs) const {
+        get_moves(state, m_delta, mvs);
+    }
+    void get_moves_to(unsigned state, moves& mvs) {
+        get_moves(state, m_delta_inv, mvs);
+    }
+private:
+    void get_moves(unsigned state, svector<moves> const& delta, moves& mvs) const {
+        unsigned_vector states;
+        get_epsilon_closure(state, delta, states);
+        for (unsigned i = 0; i < states.size(); ++i) {
+            state = states[i];
+            moves const& mv1 = delta[state];
+            for (unsigned j = 0; j < mv1.size(); ++j) {
+                if (!mv1[j].is_epsilon()) {
+                    mvs.push_back(mv1[j]);
+                }
+            }
+        }
+    }
+
+    void get_epsilon_closure(unsigned state, svector<moves> const& delta, unsigned_vector& states) const {
+        m_todo.push_back(state);
+        m_visited.insert(state);
+        while (!m_todo.empty()) {
+            state = m_todo.back();
+            states.push_back(state);
+            m_todo.pop_back();
+            moves const& mvs = delta[state];
+            for (unsigned i = 0; i < mvs.size(); ++i) {
+                unsigned tgt = mvs[i].dst();
+                if (mvs[i].is_epsilon() && !m_visited.contains(tgt)) {
+                    m_visited.insert(tgt);
+                    m_todo.push_back(tgt);
+                }
+            }
+        }
+        m_visited.reset();
+        SASSERT(m_todo.empty());   
+    }
+
+    static void append_moves(unsigned offset, automaton const& a, moves& mvs) {
+        for (unsigned i = 0; i < a.num_states(); ++i) {
+            moves const& mvs1 = a.m_delta[i];
+            for (unsigned j = 0; j < mvs1.size(); ++j) {
+                move const& mv = mvs1[j];
+                mvs.push_back(move(mv.src() + offset, mv.dst() + offset, mv.t()));
+            }
+        }
+    }
+
+    static void append_final(unsigned offset, automaton const& a, unsigned_vector& final) {
+        for (unsigned i = 0; i < a.m_final_states.size(); ++i) {
+            final.push_back(a.m_final_states[i]+offset);
+        }
+    }
+ 
+};
+
+typedef automaton<unsigned> uautomaton;
+
+
+#endif 
diff --git a/src/smt/smt_context.cpp b/src/smt/smt_context.cpp
index 26ca2e68a..738763c88 100644
--- a/src/smt/smt_context.cpp
+++ b/src/smt/smt_context.cpp
@@ -1382,7 +1382,8 @@ namespace smt {
             bool_var v = l.var();
             bool_var_data & d = get_bdata(v);
             lbool val  = get_assignment(v);
-            TRACE("propagate_atoms", tout << "propagating atom, #" << bool_var2expr(v)->get_id() << ", is_enode(): " << d.is_enode() << " " << l << "\n";);
+            TRACE("propagate_atoms", tout << "propagating atom, #" << bool_var2expr(v)->get_id() << ", is_enode(): " << d.is_enode() 
+                  << " tag: " << (d.is_eq()?"eq":"") << (d.is_theory_atom()?"th":"") << (d.is_quantifier()?"q":"") << " " << l << "\n";);
             SASSERT(val != l_undef);
             if (d.is_enode())
                 propagate_bool_var_enode(v);
@@ -1404,6 +1405,7 @@ namespace smt {
             else if (d.is_theory_atom()) {
                 theory * th = m_theories.get_plugin(d.get_theory());
                 SASSERT(th);
+                TRACE("seq", tout << d.get_theory() << "\n";);
                 th->assign_eh(v, val == l_true);
             }
             else if (d.is_quantifier()) {
diff --git a/src/smt/theory_seq.cpp b/src/smt/theory_seq.cpp
index 79779d088..1cae448b2 100644
--- a/src/smt/theory_seq.cpp
+++ b/src/smt/theory_seq.cpp
@@ -125,6 +125,7 @@ theory_seq::theory_seq(ast_manager& m):
     m_rep(m, m_dm),
     m_factory(0),
     m_ineqs(m),
+    m_in_re(m),
     m_exclude(m),
     m_axioms(m),
     m_axioms_head(0),
@@ -379,6 +380,9 @@ bool theory_seq::is_solved() {
     if (!check_ineq_coherence()) {
         return false;
     }
+    if (!m_in_re.empty()) {
+        return false;
+    }
     
     SASSERT(check_length_coherence());
 
@@ -572,7 +576,6 @@ bool theory_seq::solve_nqs() {
     bool change = false;
     context & ctx = get_context();
     for (unsigned i = 0; !ctx.inconsistent() && i < m_nqs.size(); ++i) {
-        TRACE("seq", tout << i << " " << m_nqs.size() << "\n";);
         if (!m_nqs[i].is_solved()) {
             change = solve_ne(i) || change;
         }
@@ -637,6 +640,16 @@ bool theory_seq::solve_ne(unsigned idx) {
                     literal lit(mk_eq(nl, nr, false));
                     m_trail_stack.push(push_lit(*this, idx, lit));
                     ctx.mark_as_relevant(lit);
+                    switch (ctx.get_assignment(lit)) {
+                    case l_false:
+                        mark_solved(idx);
+                        return false;
+                    case l_true:
+                        break;
+                    case l_undef:
+                        ++num_undef_lits;
+                        break;
+                    }
                 }
             }                
             m_trail_stack.push(push_dep(*this, idx, deps));
@@ -696,6 +709,8 @@ bool theory_seq::internalize_term(app* term) {
     if (m.is_bool(term)) {
         bool_var bv = ctx.mk_bool_var(term);
         ctx.set_var_theory(bv, get_id());
+        ctx.mark_as_relevant(bv);
+        TRACE("seq", tout << mk_pp(term, m) << ": " << bv << "\n";);
     }
     else {
         enode* e = 0;
@@ -751,6 +766,12 @@ void theory_seq::display(std::ostream & out) const {
             out << mk_pp(m_ineqs[i], m) << "\n";
         }
     }
+    if (!m_in_re.empty()) {
+        out << "Regex\n";
+        for (unsigned i = 0; i < m_in_re.size(); ++i) {
+            out << mk_pp(m_in_re[i], m) << "\n";
+        }
+    }
     if (!m_rep.empty()) {
         out << "Solved equations:\n";
         m_rep.display(out);
@@ -917,7 +938,12 @@ expr_ref theory_seq::expand(expr* e0, enode_pair_dependency*& eqs) {
         enode* n = get_context().get_enode(e)->get_root();
         result = n->get_owner();
         if (!m.is_model_value(result)) {
-            result = m_mg->get_some_value(m.get_sort(result));
+            if (m_util.is_char(result)) {
+                result = m_util.str.mk_char('#');
+            }
+            else {
+                result = m_mg->get_some_value(m.get_sort(result));
+            }
         }
         m_rep.update(e, result, 0);        
         TRACE("seq", tout << mk_pp(e, m) << " |-> " << result << "\n";);
@@ -1288,13 +1314,16 @@ expr_ref theory_seq::mk_skolem(symbol const& name, expr* e1,
 
 void theory_seq::propagate_eq(bool_var v, expr* e1, expr* e2) {
     context& ctx = get_context();
-    TRACE("seq", 
-          tout << mk_pp(ctx.bool_var2enode(v)->get_owner(), m) << " => " 
-          << mk_pp(e1, m) << " = " << mk_pp(e2, m) << "\n";); 
 
     SASSERT(ctx.e_internalized(e2));
     enode* n1 = ensure_enode(e1);
     enode* n2 = ensure_enode(e2);
+    if (n1->get_root() == n2->get_root()) {
+        return;
+    }
+    TRACE("seq", 
+          tout << mk_pp(ctx.bool_var2enode(v)->get_owner(), m) << " => " 
+          << mk_pp(e1, m) << " = " << mk_pp(e2, m) << "\n";); 
     literal lit(v);
     justification* js = 
         ctx.mk_justification(
@@ -1304,10 +1333,9 @@ void theory_seq::propagate_eq(bool_var v, expr* e1, expr* e2) {
     ctx.assign_eq(n1, n2, eq_justification(js));
 }
 
-void theory_seq::assign_eq(bool_var v, bool is_true) {
+void theory_seq::assign_eh(bool_var v, bool is_true) {
     context & ctx = get_context();
-    enode* n = ctx.bool_var2enode(v);
-    app*  e = n->get_owner();
+    expr* e = ctx.bool_var2expr(v);
     if (is_true) {
         expr* e1, *e2;
         expr_ref f(m);
@@ -1327,8 +1355,10 @@ void theory_seq::assign_eq(bool_var v, bool is_true) {
             f = m_util.str.mk_concat(m_util.str.mk_concat(f1, e2), f2);
             propagate_eq(v, f, e1);
         }
-        else if (m_util.str.is_in_re(e, e1, e2)) {
-            // TBD
+        else if (m_util.str.is_in_re(e)) {
+            TRACE("seq", tout << "in re: " << mk_pp(e, m) << "\n";);
+            m_trail_stack.push(push_back_vector<theory_seq, expr_ref_vector>(m_in_re));
+            m_in_re.push_back(e);
         }
         else {
             UNREACHABLE();
@@ -1403,4 +1433,22 @@ void theory_seq::relevant_eh(app* n) {
         m_util.str.is_string(n)) {
         enque_axiom(n);
     }
+    if (m_util.str.is_in_re(n) ||
+        m_util.str.is_contains(n) ||
+        m_util.str.is_suffix(n) ||
+        m_util.str.is_prefix(n)) {
+        context& ctx = get_context();
+        TRACE("seq", tout << mk_pp(n, m) << "\n";);
+        bool_var bv = ctx.get_bool_var(n);
+        switch (ctx.get_assignment(bv)) {
+        case l_false:
+            assign_eh(bv, false);
+            break;
+        case l_true:
+            assign_eh(bv, true);            
+            break;
+        case l_undef:
+            break;
+        }
+    }
 }
diff --git a/src/smt/theory_seq.h b/src/smt/theory_seq.h
index 21aabb599..43852a086 100644
--- a/src/smt/theory_seq.h
+++ b/src/smt/theory_seq.h
@@ -251,6 +251,7 @@ namespace smt {
 
         seq_factory*    m_factory;               // value factory
         expr_ref_vector m_ineqs;                 // inequalities to check solution against
+        expr_ref_vector m_in_re;                 // regular expression membership
         exclusion_table m_exclude;               // set of asserted disequalities.
         expr_ref_vector m_axioms;                // list of axioms to add.
         unsigned        m_axioms_head;           // index of first axiom to add.
@@ -277,7 +278,7 @@ namespace smt {
         virtual void internalize_eq_eh(app * atom, bool_var v);
         virtual void new_eq_eh(theory_var, theory_var);
         virtual void new_diseq_eh(theory_var, theory_var);
-        virtual void assign_eq(bool_var v, bool is_true);        
+        virtual void assign_eh(bool_var v, bool is_true);        
         virtual bool can_propagate();
         virtual void propagate();
         virtual void push_scope_eh();