diff --git a/src/ast/seq_decl_plugin.cpp b/src/ast/seq_decl_plugin.cpp
index afa3a023f..008f2b76c 100644
--- a/src/ast/seq_decl_plugin.cpp
+++ b/src/ast/seq_decl_plugin.cpp
@@ -1465,3 +1465,147 @@ bool seq_util::re::is_epsilon(expr* r) const {
 app* seq_util::re::mk_epsilon(sort* seq_sort) {
     return mk_to_re(u.str.mk_empty(seq_sort));
 }
+
+/*
+  Produces compact view of concrete concatenations such as (abcd).
+*/
+void seq_util::re::pp::compact_helper_seq(std::ostream& out, expr* s) const {
+    SASSERT(re.u.is_seq(s));
+    if (re.m.is_value(s)) {
+        SASSERT(s->get_kind() == ast_kind::AST_APP);
+        if (re.u.str.is_concat(s)) {
+            expr_ref_vector es(re.m);
+            re.u.str.get_concat(s, es);
+            for (unsigned i = 0; i < es.size(); i++)
+                if (re.u.str.is_unit(es.get(i)))
+                    seq_unit(out, es.get(i));
+                else
+                    out << mk_pp(es.get(i), re.m);
+        }
+        else if (re.u.str.is_empty(s))
+            out << "()";
+        else
+            seq_unit(out, s);
+    }
+    else
+        out << mk_pp(s, re.m);
+}
+
+/*
+  Produces output such as [a-z] for a range.
+*/
+void seq_util::re::pp::compact_helper_range(std::ostream& out, expr* s1, expr* s2) const {
+    out << "[";
+    if (re.u.str.is_unit(s1))
+        seq_unit(out, s1);
+    else 
+        out << mk_pp(s1, re.m);
+    out << "-";
+    if (re.u.str.is_unit(s2))
+        seq_unit(out, s2);
+    else
+        out << mk_pp(s1, re.m);
+    out << "]";
+}
+
+/*
+  Checks if parenthesis can be omitted in some cases in a loop body or in complement.
+*/
+bool seq_util::re::pp::can_skip_parenth(expr* r) const {
+    expr* s;
+    return ((re.is_to_re(r, s) && re.u.str.is_unit(s)) || re.is_range(r) || re.is_empty(r) || re.is_epsilon(r));
+}
+
+/*
+  Specialize output for a unit sequence converting to visible ASCII characters if possible.
+*/
+void seq_util::re::pp::seq_unit(std::ostream& out, expr* s) const {
+    expr* e;
+    if (re.u.str.is_unit(s, e)) {
+        rational r;
+        unsigned sz;
+        if (re.u.bv().is_numeral(e, r, sz) && sz == 8 && r.is_unsigned()) {
+            unsigned n = r.get_unsigned();
+            if (32 < n && n < 127)
+                out << (char)n;
+            else if (n < 16)
+                out << "\\x0" << std::hex << n;
+            else
+                out << "\\x" << std::hex << n;
+        }
+        else
+            out << mk_pp(s, re.m);
+    }
+    else
+        out << mk_pp(s, re.m);
+}
+
+/*
+  Pretty prints the regex r into the out stream
+*/
+std::ostream& seq_util::re::pp::display(std::ostream& out) const {
+    expr* r1 = nullptr, * r2 = nullptr, * s = nullptr, * s2 = nullptr;
+    unsigned lo = 0, hi = 0;
+    if (re.is_full_char(e))
+        return out << ".";
+    else if (re.is_full_seq(e))
+        return out << ".*";
+    else if (re.is_to_re(e, s)) 
+    {
+        compact_helper_seq(out, s);
+        return out;
+    }
+    else if (re.is_range(e, s, s2)) {
+        compact_helper_range(out, s, s2);
+        return out;
+    }
+    else if (re.is_epsilon(e))
+        return out << "()";
+    else if (re.is_empty(e))
+        return out << "[]";
+    else if (re.is_concat(e, r1, r2)) 
+        return out << pp(re, r1) << pp(re, r2);
+    else if (re.is_union(e, r1, r2)) 
+        return out << pp(re, r1) << "|" << pp(re, r2);
+    else if (re.is_intersection(e, r1, r2)) 
+        return out << "(" << pp(re, r1) << ")&(" << pp(re, r2) << ")";
+    else if (re.is_complement(e, r1)) 
+        if (can_skip_parenth(r1))
+            return out << "~" << pp(re, r1);
+        else 
+            return out << "~(" << pp(re, r1) << ")";
+    else if (re.is_plus(e, r1)) 
+        if (can_skip_parenth(r1))
+            return out << pp(re, r1) << "+";
+        else 
+            return out << "(" << pp(re, r1) << ")+";
+    else if (re.is_star(e, r1))
+        if (can_skip_parenth(r1))
+            return out << pp(re, r1) << "*";
+        else
+            return out << "(" << pp(re, r1) << ")*";
+    else if (re.is_loop(e, r1, lo))
+        if (can_skip_parenth(r1))
+            return out << pp(re, r1) << "{" << lo << ",}";
+        else 
+            return out << "(" << pp(re, r1) << "){" << lo << ",}";
+    else if (re.is_loop(e, r1, lo, hi))
+        if (can_skip_parenth(r1))
+            return out << pp(re, r1) << "{" << lo << "," << hi << "}";
+        else
+            return out << "(" << pp(re, r1) << "){" << lo << "," << hi << "}";
+    else if (re.is_diff(e, r1, r2)) 
+        return out << "(" << pp(re, r1) << ")\\(" << pp(re, r2) << ")";
+    else if (re.m.is_ite(e, s, r1, r2)) 
+        return out << "if(" << mk_pp(s, re.m) << "," << pp(re, r1) << "," << pp(re, r2) << ")";
+    else if (re.is_opt(e, r1))
+        if (can_skip_parenth(r1)) 
+            return out << pp(re, r1) << "?";
+        else 
+            return out << "(" << pp(re, r1) << ")?";
+    else if (re.is_reverse(e, r1)) 
+        return out << "reverse(" << pp(re, r1) << ")";
+    else
+        // Else: derivative or is_of_pred
+        return out << mk_pp(e, re.m);
+}
diff --git a/src/ast/seq_decl_plugin.h b/src/ast/seq_decl_plugin.h
index eb2feba7a..9e1639729 100644
--- a/src/ast/seq_decl_plugin.h
+++ b/src/ast/seq_decl_plugin.h
@@ -412,6 +412,7 @@ public:
         seq_util&    u;
         ast_manager& m;
         family_id    m_fid;
+
     public:
         re(seq_util& u): u(u), m(u.m), m_fid(u.m_fid) {}
 
@@ -481,6 +482,20 @@ public:
         unsigned max_length(expr* r) const;
         bool is_epsilon(expr* r) const;
         app* mk_epsilon(sort* seq_sort);
+
+        class pp {
+            seq_util::re& re;
+            expr* e;
+            bool can_skip_parenth(expr* r) const;
+            void seq_unit(std::ostream& out, expr* s) const;
+            void compact_helper_seq(std::ostream& out, expr* s) const;
+            void compact_helper_range(std::ostream& out, expr* s1, expr* s2) const;
+
+        public:
+            pp(seq_util::re& r, expr* e) : re(r), e(e) {}
+            std::ostream& display(std::ostream&) const;
+        };
+
     };
     str str;
     re  re;
@@ -499,4 +514,8 @@ public:
 
 };
 
+inline std::ostream& operator<<(std::ostream& out, seq_util::re::pp const & p) { return p.display(out); }
+
+
+
 
diff --git a/src/smt/seq_regex.cpp b/src/smt/seq_regex.cpp
index 06b5e7f89..d025c2eee 100644
--- a/src/smt/seq_regex.cpp
+++ b/src/smt/seq_regex.cpp
@@ -791,6 +791,10 @@ namespace smt {
             STRACE("seq_regex_brief", tout << "(MAX SIZE REACHED) ";);
             return false;
         }
+        STRACE("seq_regex", tout << "Updating state graph for regex "
+                                 << mk_pp(r, m) << ") ";);
+        if (!m_state_graph.is_seen(r_id))
+            STRACE("state_graph", tout << std::endl << "state(" << r_id << ") = " << seq_util::re::pp(re(), r) << std::endl;);
         // Add state
         m_state_graph.add_state(r_id);
         STRACE("state_graph", tout << "regex(" << r_id << ") = " << mk_pp(r, m) << std::endl;);
@@ -811,7 +815,10 @@ namespace smt {
             for (auto const& dr: derivatives) {
                 unsigned dr_id = get_state_id(dr);
                 STRACE("seq_regex_verbose", tout
-                    << "  traversing deriv: " << dr_id << " " << std::endl;);
+                    << std::endl << "  traversing deriv: " << dr_id << " ";);
+                if (!m_state_graph.is_seen(dr_id))
+                    STRACE("state_graph", tout << "state(" << dr_id << ") = " << seq_util::re::pp(re(), dr) << std::endl;);
+                // Add state
                 m_state_graph.add_state(dr_id);
                 STRACE("state_graph", tout << "regex(" << dr_id << ") = " << mk_pp(dr, m) << std::endl;);
                 bool maybecycle = can_be_in_cycle(r, dr);