diff --git a/scripts/mk_util.py b/scripts/mk_util.py
index 33f70c98d..fc0d3b5e0 100644
--- a/scripts/mk_util.py
+++ b/scripts/mk_util.py
@@ -71,6 +71,7 @@ VERBOSE=True
 DEBUG_MODE=False
 SHOW_CPPS = True
 VS_X64 = False
+VS_ARM = False
 LINUX_X64 = True
 ONLY_MAKEFILES = False
 Z3PY_SRC_DIR=None
@@ -99,6 +100,7 @@ USE_OMP=True
 FPMATH="Default"
 FPMATH_FLAGS="-mfpmath=sse -msse -msse2"
 
+
 def check_output(cmd):
     out = subprocess.Popen(cmd, stdout=subprocess.PIPE).communicate()[0]
     if out != None:
@@ -1557,6 +1559,8 @@ class DotNetDLLComponent(Component):
         if IS_WINDOWS:
             if VS_X64:
                 cscCmdLine.extend(['/platform:x64'])
+            elif VS_ARM:
+                cscCmdLine.extend(['/platform:arm'])
             else:
                 cscCmdLine.extend(['/platform:x86'])
         else:
@@ -1997,6 +2001,8 @@ class DotNetExampleComponent(ExampleComponent):
             out.write('\t%s /out:%s /reference:%s /debug:full /reference:System.Numerics.dll' % (CSC, exefile, dll))
             if VS_X64:
                 out.write(' /platform:x64')
+            elif VS_ARM:
+                out.write(' /platform:arm')                
             else:
                 out.write(' /platform:x86')
             for csfile in get_cs_files(self.ex_dir):
@@ -2186,18 +2192,21 @@ def mk_config():
                 'AR_FLAGS=/nologo\n'
                 'LINK_FLAGS=/nologo /MDd\n'
                 'SLINK_FLAGS=/nologo /LDd\n')
-            if not VS_X64:
-                config.write(
-                    'CXXFLAGS=/c /Zi /nologo /W3 /WX- /Od /Oy- /D WIN32 /D _DEBUG /D Z3DEBUG %s /D _CONSOLE /D _TRACE /D _WINDOWS /Gm- /EHsc /RTC1 /MDd /GS /fp:precise /Zc:wchar_t /Zc:forScope /Gd /analyze- /arch:SSE2\n' % extra_opt)
-                config.write(
-                    'LINK_EXTRA_FLAGS=/link /DEBUG /MACHINE:X86 /SUBSYSTEM:CONSOLE /INCREMENTAL:NO /STACK:8388608 /OPT:REF /OPT:ICF /TLBID:1 /DYNAMICBASE /NXCOMPAT\n'
-                    'SLINK_EXTRA_FLAGS=/link /DEBUG /MACHINE:X86 /SUBSYSTEM:WINDOWS /INCREMENTAL:NO /STACK:8388608 /OPT:REF /OPT:ICF /TLBID:1 /DYNAMICBASE:NO\n')
-            else:
+            if VS_X64:
                 config.write(
                     'CXXFLAGS=/c /Zi /nologo /W3 /WX- /Od /Oy- /D WIN32 /D _AMD64_ /D _DEBUG /D Z3DEBUG %s /D _CONSOLE /D _TRACE /D _WINDOWS /Gm- /EHsc /RTC1 /MDd /GS /fp:precise /Zc:wchar_t /Zc:forScope /Gd /analyze-\n' % extra_opt)
                 config.write(
                     'LINK_EXTRA_FLAGS=/link /DEBUG /MACHINE:X64 /SUBSYSTEM:CONSOLE /INCREMENTAL:NO /STACK:8388608 /OPT:REF /OPT:ICF /TLBID:1 /DYNAMICBASE /NXCOMPAT\n'
                     'SLINK_EXTRA_FLAGS=/link /DEBUG /MACHINE:X64 /SUBSYSTEM:WINDOWS /INCREMENTAL:NO /STACK:8388608 /OPT:REF /OPT:ICF /TLBID:1 /DYNAMICBASE:NO\n')
+            elif VS_ARM:
+                print "ARM on VS is unsupported"
+                exit(1)
+            else:
+                config.write(
+                    'CXXFLAGS=/c /Zi /nologo /W3 /WX- /Od /Oy- /D WIN32 /D _DEBUG /D Z3DEBUG %s /D _CONSOLE /D _TRACE /D _WINDOWS /Gm- /EHsc /RTC1 /MDd /GS /fp:precise /Zc:wchar_t /Zc:forScope /Gd /analyze- /arch:SSE2\n' % extra_opt)
+                config.write(
+                    'LINK_EXTRA_FLAGS=/link /DEBUG /MACHINE:X86 /SUBSYSTEM:CONSOLE /INCREMENTAL:NO /STACK:8388608 /OPT:REF /OPT:ICF /TLBID:1 /DYNAMICBASE /NXCOMPAT\n'
+                    'SLINK_EXTRA_FLAGS=/link /DEBUG /MACHINE:X86 /SUBSYSTEM:WINDOWS /INCREMENTAL:NO /STACK:8388608 /OPT:REF /OPT:ICF /TLBID:1 /DYNAMICBASE:NO\n')
         else:
             # Windows Release mode
             LTCG=' /LTCG' if SLOW_OPTIMIZE else ''
@@ -2209,18 +2218,23 @@ def mk_config():
                 % LTCG)
             if TRACE:
                 extra_opt = '%s /D _TRACE ' % extra_opt
-            if not VS_X64:
-                config.write(
-                    'CXXFLAGS=/nologo /c%s /Zi /W3 /WX- /O2 /Oy- /D _EXTERNAL_RELEASE /D WIN32 /D NDEBUG %s /D _CONSOLE /D _WINDOWS /D ASYNC_COMMANDS /Gm- /EHsc /MD /GS /fp:precise /Zc:wchar_t /Zc:forScope /Gd /analyze- /arch:SSE2\n' % (GL, extra_opt))
-                config.write(
-                    'LINK_EXTRA_FLAGS=/link%s /DEBUG /MACHINE:X86 /SUBSYSTEM:CONSOLE /INCREMENTAL:NO /STACK:8388608 /OPT:REF /OPT:ICF /TLBID:1 /DYNAMICBASE /NXCOMPAT\n'
-                    'SLINK_EXTRA_FLAGS=/link%s /DEBUG /MACHINE:X86 /SUBSYSTEM:WINDOWS /INCREMENTAL:NO /STACK:8388608 /OPT:REF /OPT:ICF /TLBID:1 /DYNAMICBASE:NO\n' % (LTCG, LTCG))
-            else:
+            if VS_X64:
                 config.write(
                     'CXXFLAGS=/c%s /Zi /nologo /W3 /WX- /O2 /D _EXTERNAL_RELEASE /D WIN32 /D NDEBUG %s /D _LIB /D _WINDOWS /D _AMD64_ /D _UNICODE /D UNICODE /Gm- /EHsc /MD /GS /fp:precise /Zc:wchar_t /Zc:forScope /Gd /TP\n' % (GL, extra_opt))
                 config.write(
                     'LINK_EXTRA_FLAGS=/link%s /MACHINE:X64 /SUBSYSTEM:CONSOLE /INCREMENTAL:NO /STACK:8388608\n'
                     'SLINK_EXTRA_FLAGS=/link%s /MACHINE:X64 /SUBSYSTEM:WINDOWS /INCREMENTAL:NO /STACK:8388608\n' % (LTCG, LTCG))
+            elif VS_ARM:
+                print "ARM on VS is unsupported"
+                exit(1)
+            else:
+                config.write(
+                    'CXXFLAGS=/nologo /c%s /Zi /W3 /WX- /O2 /Oy- /D _EXTERNAL_RELEASE /D WIN32 /D NDEBUG %s /D _CONSOLE /D _WINDOWS /D ASYNC_COMMANDS /Gm- /EHsc /MD /GS /fp:precise /Zc:wchar_t /Zc:forScope /Gd /analyze- /arch:SSE2\n' % (GL, extra_opt))
+                config.write(
+                    'LINK_EXTRA_FLAGS=/link%s /DEBUG /MACHINE:X86 /SUBSYSTEM:CONSOLE /INCREMENTAL:NO /STACK:8388608 /OPT:REF /OPT:ICF /TLBID:1 /DYNAMICBASE /NXCOMPAT\n'
+                    'SLINK_EXTRA_FLAGS=/link%s /DEBUG /MACHINE:X86 /SUBSYSTEM:WINDOWS /INCREMENTAL:NO /STACK:8388608 /OPT:REF /OPT:ICF /TLBID:1 /DYNAMICBASE:NO\n' % (LTCG, LTCG))
+
+                
 
         # End of Windows VS config.mk
         if is_verbose():
@@ -2446,6 +2460,9 @@ def mk_makefile():
             if VS_X64:
                 print("  platform: x64\n")
                 print("To build Z3, open a [Visual Studio x64 Command Prompt], then")
+            elif VS_ARM:
+                print("  platform: ARM\n")
+                print("To build Z3, open a [Visual Studio ARM Command Prompt], then")                
             else:
                 print("  platform: x86")
                 print("To build Z3, open a [Visual Studio Command Prompt], then")
diff --git a/src/ast/ast_smt_pp.cpp b/src/ast/ast_smt_pp.cpp
index 9279f50fe..82137483a 100644
--- a/src/ast/ast_smt_pp.cpp
+++ b/src/ast/ast_smt_pp.cpp
@@ -30,6 +30,7 @@ Revision History:
 #include"for_each_ast.h"
 #include"decl_collector.h"
 #include"smt2_util.h"
+#include"seq_decl_plugin.h"
 
 // ---------------------------------------
 // smt_renaming
@@ -160,6 +161,7 @@ class smt_printer {
     unsigned         m_num_lets;
     arith_util       m_autil;
     bv_util          m_bvutil;
+    seq_util         m_sutil;
     family_id        m_basic_fid;
     family_id        m_bv_fid;
     family_id        m_arith_fid;
@@ -247,6 +249,10 @@ class smt_printer {
         }
 
         if (m_is_smt2) {
+            if (is_sort_symbol && sym == symbol("String")) {
+                m_out << "String";
+                return;
+            }
             if (is_sort_symbol && sym != symbol("BitVec")) {
                 m_out << "(" << sym << " ";                
             }
@@ -397,6 +403,7 @@ class smt_printer {
         bool is_int, pos;
         buffer<symbol> names;
         unsigned bv_size;
+        zstring s;    
         unsigned num_args = n->get_num_args();
         func_decl* decl = n->get_decl();
         if (m_autil.is_numeral(n, val, is_int)) {
@@ -415,6 +422,19 @@ class smt_printer {
                 display_rational(val, is_int);
             }
         }
+        else if (m_sutil.str.is_string(n, s)) {
+            std::string encs = s.encode();
+            m_out << "\"";
+            for (unsigned i = 0; i < encs.length(); ++i) {
+                if (encs[i] == '\"') {
+                    m_out << "\"\"";
+                }
+                else {
+                    m_out << encs[i];
+                }
+            }
+            m_out << "\"";              
+        }
         else if (m_bvutil.is_numeral(n, val, bv_size)) {
             if (m_is_smt2) {
                 m_out << "(_ bv" << val << " " << bv_size << ")";
@@ -797,6 +817,7 @@ public:
         m_num_lets(0),
         m_autil(m),
         m_bvutil(m),
+        m_sutil(m),
         m_logic(logic),
         m_AUFLIRA("AUFLIRA"),
         // It's much easier to read those testcases with that.
diff --git a/src/ast/rewriter/seq_rewriter.cpp b/src/ast/rewriter/seq_rewriter.cpp
index 13ba7d67d..a26fcfe2c 100644
--- a/src/ast/rewriter/seq_rewriter.cpp
+++ b/src/ast/rewriter/seq_rewriter.cpp
@@ -437,7 +437,12 @@ br_status seq_rewriter::mk_seq_contains(expr* a, expr* b, expr_ref& result) {
     m_util.str.get_concat(a, as);
     m_util.str.get_concat(b, bs);
     bool all_values = true;
-    
+   
+    if (bs.empty()) {
+        result = m().mk_true();
+        return BR_DONE;
+    }
+
     for (unsigned i = 0; all_values && i < bs.size(); ++i) { 
         all_values = m().is_value(bs[i].get());
     }
@@ -459,6 +464,39 @@ br_status seq_rewriter::mk_seq_contains(expr* a, expr* b, expr_ref& result) {
         result = m().mk_false();
         return BR_DONE;
     }
+
+    unsigned lenA = 0, lenB = 0;
+    bool lA = min_length(as.size(), as.c_ptr(), lenA);
+    if (lA) {
+        bool lB = min_length(bs.size(), bs.c_ptr(), lenB);
+        if (lenB > lenA) {
+            result = m().mk_false();
+            return BR_DONE;
+        }
+    }
+
+
+    if (as.empty()) {
+        result = m().mk_eq(b, m_util.str.mk_empty(m().get_sort(b)));
+        return BR_REWRITE2;
+    }
+
+    unsigned offs = 0;
+    unsigned sz = as.size();
+    expr* b0 = bs[0].get();
+    expr* bL = bs[bs.size()-1].get();
+    for (; offs < as.size() && m().are_distinct(b0, as[offs].get()); ++offs) {};
+    for (; sz > offs && m().are_distinct(bL, as[sz-1].get()); --sz) {}
+    if (offs == sz) {
+        result = m().mk_eq(b, m_util.str.mk_empty(m().get_sort(b)));
+        return BR_REWRITE2;
+    }
+    if (offs > 0 || sz < as.size()) {
+        SASSERT(sz > offs);
+        result = m_util.str.mk_contains(m_util.str.mk_concat(sz-offs, as.c_ptr()+offs), b);
+        return BR_REWRITE2;
+    }
+
     return BR_FAILED;
 }
 
diff --git a/src/ast/seq_decl_plugin.h b/src/ast/seq_decl_plugin.h
index 4100fe6cc..6200d910f 100644
--- a/src/ast/seq_decl_plugin.h
+++ b/src/ast/seq_decl_plugin.h
@@ -222,16 +222,16 @@ public:
         str(seq_util& u): u(u), m(u.m), m_fid(u.m_fid) {}
 
         sort* mk_seq(sort* s) { parameter param(s); return m.mk_sort(m_fid, SEQ_SORT, 1, &param); }
-        sort* mk_string_sort() { return m.mk_sort(m_fid, _STRING_SORT, 0, 0); }
-        app* mk_empty(sort* s) { return m.mk_const(m.mk_func_decl(m_fid, OP_SEQ_EMPTY, 0, 0, 0, (expr*const*)0, s)); }
+        sort* mk_string_sort() const { return m.mk_sort(m_fid, _STRING_SORT, 0, 0); }
+        app* mk_empty(sort* s) const { return m.mk_const(m.mk_func_decl(m_fid, OP_SEQ_EMPTY, 0, 0, 0, (expr*const*)0, s)); }
         app* mk_string(zstring const& s);
         app* mk_string(symbol const& s) { return u.seq.mk_string(s); }
         app* mk_char(char ch);
-        app* mk_concat(expr* a, expr* b) { expr* es[2] = { a, b }; return m.mk_app(m_fid, OP_SEQ_CONCAT, 2, es); }
+        app* mk_concat(expr* a, expr* b) const { expr* es[2] = { a, b }; return m.mk_app(m_fid, OP_SEQ_CONCAT, 2, es); }
         app* mk_concat(expr* a, expr* b, expr* c) { return mk_concat(a, mk_concat(b, c)); }
-        expr* mk_concat(unsigned n, expr* const* es) { if (n == 1) return es[0]; SASSERT(n > 1); return m.mk_app(m_fid, OP_SEQ_CONCAT, n, es); }
-        expr* mk_concat(expr_ref_vector const& es) { return mk_concat(es.size(), es.c_ptr()); }
-        app* mk_length(expr* a) { return m.mk_app(m_fid, OP_SEQ_LENGTH, 1, &a); }
+        expr* mk_concat(unsigned n, expr* const* es) const { if (n == 1) return es[0]; SASSERT(n > 1); return m.mk_app(m_fid, OP_SEQ_CONCAT, n, es); }
+        expr* mk_concat(expr_ref_vector const& es) const { return mk_concat(es.size(), es.c_ptr()); }
+        app* mk_length(expr* a) const { return m.mk_app(m_fid, OP_SEQ_LENGTH, 1, &a); }
         app* mk_substr(expr* a, expr* b, expr* c) { expr* es[3] = { a, b, c }; return m.mk_app(m_fid, OP_SEQ_EXTRACT, 3, es); }
         app* mk_contains(expr* a, expr* b) { expr* es[2] = { a, b }; return m.mk_app(m_fid, OP_SEQ_CONTAINS, 2, es); }
         app* mk_prefix(expr* a, expr* b) { expr* es[2] = { a, b }; return m.mk_app(m_fid, OP_SEQ_PREFIX, 2, es); }
diff --git a/src/smt/smt_conflict_resolution.cpp b/src/smt/smt_conflict_resolution.cpp
index 3aa02c0b6..86593b0f2 100644
--- a/src/smt/smt_conflict_resolution.cpp
+++ b/src/smt/smt_conflict_resolution.cpp
@@ -99,22 +99,29 @@ namespace smt {
        This method may update m_antecedents, m_todo_js and m_todo_eqs.
     */
     void conflict_resolution::eq_justification2literals(enode * lhs, enode * rhs, eq_justification js) {
+        ast_manager& m = get_manager();
         SASSERT(m_antecedents);
+        TRACE("conflict_detail", tout << mk_pp(lhs->get_owner(), m) << " = " << mk_pp(rhs->get_owner(), m);
+              switch (js.get_kind()) {
+              case eq_justification::AXIOM: tout << " axiom\n";  break;
+              case eq_justification::EQUATION:
+                  tout << " was asserted\nliteral: "; m_ctx.display_literal(tout, js.get_literal()); tout << "\n";
+                  break;
+              case eq_justification::JUSTIFICATION: tout << " justification\n";  break;
+              case eq_justification::CONGRUENCE: tout << " congruence\n"; break;
+              default:  break;
+              });
+
         switch(js.get_kind()) {
         case eq_justification::AXIOM:
-            TRACE("conflict_detail", tout << "#" << lhs->get_owner_id() << " = " << rhs->get_owner_id() << " axiom\n";); 
             break;
         case eq_justification::EQUATION:
-            TRACE("conflict_detail", tout << "#" << lhs->get_owner_id() << " = " << rhs->get_owner_id() << " was asserted\n"
-                  << "literal: "; m_ctx.display_literal(tout, js.get_literal()); tout << "\n";); 
             m_antecedents->push_back(js.get_literal());
             break;
         case eq_justification::JUSTIFICATION:
-            TRACE("conflict_detail", tout << "#" << lhs->get_owner_id() << " = " << rhs->get_owner_id() << " justification\n";);
             mark_justification(js.get_justification());
             break;
         case eq_justification::CONGRUENCE: {
-            TRACE("conflict_detail", tout << "#" << lhs->get_owner_id() << " = " << rhs->get_owner_id() << " congruence\n";);
             CTRACE("dyn_ack_target", !lhs->is_eq(), tout << "dyn_ack_target2: " << lhs->get_owner_id() << " " << rhs->get_owner_id() << "\n";);
             m_dyn_ack_manager.used_cg_eh(lhs->get_owner(), rhs->get_owner());
             unsigned num_args = lhs->get_num_args();
@@ -206,7 +213,6 @@ namespace smt {
         justification_vector::iterator it  = m_todo_js.begin() + old_js_qhead;
         justification_vector::iterator end = m_todo_js.end();
         for (; it != end; ++it) {
-            TRACE("conflict_detail", tout << "unmarking: " << *it << "\n";);
             (*it)->unset_mark();
         }
         m_todo_js.shrink(old_js_qhead);
@@ -371,11 +377,9 @@ namespace smt {
               tout << "conflict_lvl: " << m_conflict_lvl << " scope_lvl: " << m_ctx.get_scope_level() << " base_lvl: " << m_ctx.get_base_level() 
               << " search_lvl: " << m_ctx.get_search_level() << "\n";
               tout << "js.kind: " << js.get_kind() << "\n";
-              tout << "consequent: " << consequent << "\n";
-	      for (unsigned i = 0; i < m_assigned_literals.size(); ++i) {
-                  tout << m_assigned_literals[i] << " ";
-	      }
-	      tout << "\n";
+              tout << "consequent: " << consequent << ": ";
+              m_ctx.display_literal_verbose(tout, consequent); tout << "\n";
+              m_ctx.display(tout, js); tout << "\n";
 	      );
 
         // m_conflict_lvl can be smaller than m_ctx.get_search_level() when:
@@ -416,12 +420,12 @@ namespace smt {
         
         TRACE("conflict",
               tout << "before minimization:\n";
-              m_ctx.display_literals(tout, m_lemma.size(), m_lemma.c_ptr());
+              m_ctx.display_literals(tout, m_lemma);
               tout << "\n";);
         
         TRACE("conflict_verbose",
               tout << "before minimization:\n";
-              m_ctx.display_literals_verbose(tout, m_lemma.size(), m_lemma.c_ptr());
+              m_ctx.display_literals_verbose(tout, m_lemma);
               tout << "\n";);
         
         if (m_params.m_minimize_lemmas)
@@ -429,12 +433,16 @@ namespace smt {
         
         TRACE("conflict",
               tout << "after minimization:\n";
-              m_ctx.display_literals(tout, m_lemma.size(), m_lemma.c_ptr());
+              m_ctx.display_literals(tout, m_lemma);
               tout << "\n";);
         
         TRACE("conflict_verbose",
               tout << "after minimization:\n";
-              m_ctx.display_literals_verbose(tout, m_lemma.size(), m_lemma.c_ptr());
+              m_ctx.display_literals_verbose(tout, m_lemma);
+              tout << "\n";);
+
+        TRACE("conflict_bug",
+              m_ctx.display_literals_verbose(tout, m_lemma);
               tout << "\n";);
         
         literal_vector::iterator it  = m_lemma.begin();
@@ -1423,7 +1431,7 @@ namespace smt {
         }
 
     end_unsat_core:
-        TRACE("unsat_core", tout << "assumptions:\n"; m_ctx.display_literals(tout, m_assumptions.size(), m_assumptions.c_ptr()); tout << "\n";);
+        TRACE("unsat_core", tout << "assumptions:\n"; m_ctx.display_literals(tout, m_assumptions); tout << "\n";);
         reset_unmark_and_justifications(0, 0);
     }
     
diff --git a/src/smt/smt_conflict_resolution.h b/src/smt/smt_conflict_resolution.h
index 6d8abbf23..daccadbb7 100644
--- a/src/smt/smt_conflict_resolution.h
+++ b/src/smt/smt_conflict_resolution.h
@@ -114,7 +114,6 @@ namespace smt {
 
         void mark_justification(justification * js) {
             if (!js->is_marked()) {
-                TRACE("conflict_detail", tout << "marking: " << js << "\n";);
                 js->set_mark();
                 m_todo_js.push_back(js);
             }
@@ -126,7 +125,7 @@ namespace smt {
                     std::swap(n1, n2);
                 enode_pair p(n1, n2);
                 if (m_already_processed_eqs.insert_if_not_there(p)) {
-                    TRACE("conflict_detail", tout << "marking eq #" << p.first->get_owner_id() << " = #" << 
+                    TRACE("conflict_detail_verbose", tout << "marking eq #" << p.first->get_owner_id() << " = #" << 
                           p.second->get_owner_id() << "\n";);
                     m_todo_eqs.push_back(p);
                     SASSERT(m_already_processed_eqs.contains(p));
@@ -168,9 +167,8 @@ namespace smt {
         void eq_justification2literals(enode * lhs, enode * rhs, eq_justification js);
         void eq_branch2literals(enode * n1, enode * n2);
         void eq2literals(enode * n1, enode * n2);
-        void justification2literals_core(justification * js, literal_vector & result);
+        void justification2literals_core(justification * js, literal_vector & result) ;
         void unmark_justifications(unsigned old_js_qhead);
-        void justification2literals(justification * js, literal_vector & result);
 
         literal_vector m_tmp_literal_vector;
 
@@ -256,6 +254,9 @@ namespace smt {
         literal_vector::const_iterator end_unsat_core() const {
             return m_assumptions.end();
         }
+
+        void justification2literals(justification * js, literal_vector & result);
+
     };
 
     inline void mark_literals(conflict_resolution & cr, unsigned sz, literal const * ls) {
diff --git a/src/smt/smt_context.cpp b/src/smt/smt_context.cpp
index 1a8658c99..7d07f3997 100644
--- a/src/smt/smt_context.cpp
+++ b/src/smt/smt_context.cpp
@@ -295,7 +295,7 @@ namespace smt {
     
     void context::assign_core(literal l, b_justification j, bool decision) {
         TRACE("assign_core", tout << (decision?"decision: ":"propagating: ") << l << " ";              
-              display_literal(tout, l); tout << " level: " << m_scope_lvl << "\n";
+              display_literal_verbose(tout, l); tout << " level: " << m_scope_lvl << "\n";
               display(tout, j););
         SASSERT(l.var() < static_cast<int>(m_b_internalized_stack.size()));
         m_assigned_literals.push_back(l);
diff --git a/src/smt/smt_context.h b/src/smt/smt_context.h
index 85fd63033..b918be2cf 100644
--- a/src/smt/smt_context.h
+++ b/src/smt/smt_context.h
@@ -1176,8 +1176,18 @@ namespace smt {
 
         void display_literals(std::ostream & out, unsigned num_lits, literal const * lits) const;
 
+        void display_literals(std::ostream & out, literal_vector const& lits) const {
+            display_literals(out, lits.size(), lits.c_ptr());
+        }
+
+        void display_literal_verbose(std::ostream & out, literal lit) const;
+
         void display_literals_verbose(std::ostream & out, unsigned num_lits, literal const * lits) const;
 
+        void display_literals_verbose(std::ostream & out, literal_vector const& lits) const {
+            display_literals_verbose(out, lits.size(), lits.c_ptr());
+        }
+
         void display_watch_list(std::ostream & out, literal l) const;
 
         void display_watch_lists(std::ostream & out) const;
diff --git a/src/smt/smt_context_pp.cpp b/src/smt/smt_context_pp.cpp
index d04165c5b..1f5566a03 100644
--- a/src/smt/smt_context_pp.cpp
+++ b/src/smt/smt_context_pp.cpp
@@ -96,6 +96,10 @@ namespace smt {
         display_compact(out, num_lits, lits, m_bool_var2expr.c_ptr());
     }
 
+    void context::display_literal_verbose(std::ostream & out, literal lit) const {
+        display_literals_verbose(out, 1, &lit);
+    }
+
     void context::display_literals_verbose(std::ostream & out, unsigned num_lits, literal const * lits) const {
         display_verbose(out, m_manager, num_lits, lits, m_bool_var2expr.c_ptr(), "\n");
     }
@@ -599,12 +603,16 @@ namespace smt {
         case b_justification::CLAUSE: {
             clause * cls = j.get_clause();
             out << "clause ";
-            display_literals(out, cls->get_num_literals(), cls->begin_literals());
+            if (cls) display_literals_verbose(out, cls->get_num_literals(), cls->begin_literals());
             break;
         }
-        case b_justification::JUSTIFICATION:
-            out << "justification";
+        case b_justification::JUSTIFICATION: {
+            out << "justification ";
+            literal_vector lits;
+            const_cast<conflict_resolution&>(*m_conflict_resolution).justification2literals(j.get_justification(), lits);
+            display_literals_verbose(out, lits.size(), lits.c_ptr());
             break;
+        }
         default:
             UNREACHABLE();
             break;
diff --git a/src/smt/theory_seq.cpp b/src/smt/theory_seq.cpp
index 40b9fa04b..cfd043895 100644
--- a/src/smt/theory_seq.cpp
+++ b/src/smt/theory_seq.cpp
@@ -258,6 +258,11 @@ final_check_status theory_seq::final_check_eh() {
         TRACE("seq", tout << ">>propagate_automata\n";);
         return FC_CONTINUE;
     }
+    if (check_contains()) {
+        ++m_stats.m_propagate_contains;
+        TRACE("seq", tout << ">>propagate_contains\n";);
+        return FC_CONTINUE;
+    }
     if (is_solved()) {
         TRACE("seq", tout << ">>is_solved\n";);
         return FC_DONE;
@@ -288,7 +293,7 @@ bool theory_seq::branch_variable() {
         unsigned id = e.id();
 
         s = find_branch_start(2*id);
-        TRACE("seq", tout << s << " " << 2*id << ": " << e.ls() << " = " << e.rs() << "\n";);
+        TRACE("seq", tout << s << " " << id << ": " << e.ls() << " = " << e.rs() << "\n";);
         bool found = find_branch_candidate(s, e.dep(), e.ls(), e.rs());
         insert_branch_start(2*id, s);
         if (found) {
@@ -337,15 +342,15 @@ bool theory_seq::find_branch_candidate(unsigned& start, dependency* dep, expr_re
         return false;
     }
 
+    TRACE("seq", tout << mk_pp(l, m) << ": " << get_context().get_scope_level() << " - start:" << start << "\n";);
+
     expr_ref v0(m);
     v0 = m_util.str.mk_empty(m.get_sort(l));
-    literal_vector lits;
     if (can_be_equal(ls.size() - 1, ls.c_ptr() + 1, rs.size(), rs.c_ptr())) {
         if (l_false != assume_equality(l, v0)) {
             TRACE("seq", tout << mk_pp(l, m) << " " << v0 << "\n";);
             return true;
         }
-        lits.push_back(~mk_eq_empty(l));
     }
     for (; start < rs.size(); ++start) {
         unsigned j = start;
@@ -370,14 +375,31 @@ bool theory_seq::find_branch_candidate(unsigned& start, dependency* dep, expr_re
         all_units &= m_util.str.is_unit(rs[j]);
     }
     if (all_units) {
+        context& ctx = get_context();
+        literal_vector lits;
+        lits.push_back(~mk_eq_empty(l));
         for (unsigned i = 0; i < rs.size(); ++i) {
             if (can_be_equal(ls.size() - 1, ls.c_ptr() + 1, rs.size() - i - 1, rs.c_ptr() + i + 1)) {
                 v0 = mk_concat(i + 1, rs.c_ptr());
                 lits.push_back(~mk_eq(l, v0, false));
             }
         }
+        for (unsigned i = 0; i < lits.size(); ++i) {
+            switch (ctx.get_assignment(lits[i])) {
+            case l_true:  break;
+            case l_false: start = 0; return true;
+            case l_undef: ctx.force_phase(~lits[i]); start = 0; return true;
+            }
+        }
         set_conflict(dep, lits);
-        TRACE("seq", tout << mk_pp(l, m) << " " << v0 << "\n";);
+        TRACE("seq", 
+              tout << "start: " << start << "\n";
+              for (unsigned i = 0; i < lits.size(); ++i) {
+                  ctx.display_literal_verbose(tout << lits[i] << ": ", lits[i]); 
+                  tout << "\n";
+                  ctx.display(tout, ctx.get_justification(lits[i].var()));
+                  tout << "\n";
+              });
         return true;
     }
     return false;
@@ -429,10 +451,19 @@ lbool theory_seq::assume_equality(expr* l, expr* r) {
     if (n1->get_root() == n2->get_root()) {
         return l_true;
     }
+    if (ctx.is_diseq(n1, n2)) {
+        return l_false;
+    }
+    if (false && ctx.is_diseq_slow(n1, n2)) {
+        return l_false;
+    }
     ctx.mark_as_relevant(n1);
     ctx.mark_as_relevant(n2);
-    ctx.assume_eq(n1, n2);
-    return l_undef;
+    if (!ctx.assume_eq(n1, n2)) {
+        return l_false;
+    }
+    return ctx.get_assignment(mk_eq(l, r, false));
+    //return l_undef;
 }
 
 
@@ -483,29 +514,50 @@ bool theory_seq::propagate_length_coherence(expr* e) {
     return true;
 }
 
+
 bool theory_seq::check_length_coherence(expr* e) {
     if (is_var(e) && m_rep.is_root(e)) {
-        expr_ref emp(m_util.str.mk_empty(m.get_sort(e)), m);
-        expr_ref head(m), tail(m);
-        if (!propagate_length_coherence(e) &&
-            l_false == assume_equality(e, emp)) {
+        if (!check_length_coherence0(e)) {
+            expr_ref emp(m_util.str.mk_empty(m.get_sort(e)), m);
+            expr_ref head(m), tail(m);
             // e = emp \/ e = unit(head.elem(e))*tail(e)
             mk_decompose(e, head, tail);
             expr_ref conc = mk_concat(head, tail);
-            propagate_is_conc(e, conc);
-            assume_equality(tail, emp);
-        }
-        else if (!get_context().at_base_level()) {
-            m_trail_stack.push(push_replay(alloc(replay_length_coherence, m, e)));
+            if (propagate_is_conc(e, conc)) {
+                assume_equality(tail, emp);
+            }
         }
         return true;
     }
     return false;
 }
 
+bool theory_seq::check_length_coherence0(expr* e) {
+    if (is_var(e) && m_rep.is_root(e)) {
+        expr_ref emp(m_util.str.mk_empty(m.get_sort(e)), m);
+        if (propagate_length_coherence(e) ||
+            l_false != assume_equality(e, emp)) {
+            if (!get_context().at_base_level()) {
+                m_trail_stack.push(push_replay(alloc(replay_length_coherence, m, e)));
+            }
+            return true;
+        }
+    }
+    return false;
+}
+
 bool theory_seq::check_length_coherence() {
 
     obj_hashtable<expr>::iterator it = m_length.begin(), end = m_length.end();
+#if 1
+    for (; it != end; ++it) {
+        expr* e = *it;
+        if (check_length_coherence0(e)) {
+            return true;
+        }
+    }
+    it = m_length.begin();
+#endif
     for (; it != end; ++it) {
         expr* e = *it;
         if (check_length_coherence(e)) {
@@ -570,14 +622,19 @@ void theory_seq::propagate_non_empty(literal lit, expr* s) {
     propagate_lit(0, 1, &lit, ~mk_eq_empty(s));
 }
 
-void theory_seq::propagate_is_conc(expr* e, expr* conc) {
+bool theory_seq::propagate_is_conc(expr* e, expr* conc) {
     TRACE("seq", tout << mk_pp(conc, m) << " is non-empty\n";);
     context& ctx = get_context();
     literal lit = ~mk_eq_empty(e);
-    SASSERT(ctx.get_assignment(lit) == l_true);
-    propagate_lit(0, 1, &lit, mk_eq(e, conc, false));
-    expr_ref e1(e, m), e2(conc, m);
-    new_eq_eh(m_dm.mk_leaf(assumption(lit)), ctx.get_enode(e1), ctx.get_enode(e2));
+    if (ctx.get_assignment(lit) == l_true) {
+        propagate_lit(0, 1, &lit, mk_eq(e, conc, false));
+        expr_ref e1(e, m), e2(conc, m);
+        new_eq_eh(m_dm.mk_leaf(assumption(lit)), ctx.get_enode(e1), ctx.get_enode(e2));
+        return true;
+    }
+    else {
+        return false;
+    }
 }
 
 bool theory_seq::is_nth(expr* e) const {
@@ -717,6 +774,23 @@ bool theory_seq::check_extensionality() {
     return true;
 }
 
+/*
+  \brief check negated contains constriants.
+ */
+bool theory_seq::check_contains() {
+    context & ctx = get_context();
+    for (unsigned i = 0; !ctx.inconsistent() && i < m_ncs.size(); ++i) {
+        if (solve_nc(i)) {
+            if (i + 1 != m_ncs.size()) {
+                nc n = m_ncs[m_ncs.size()-1];
+                m_ncs.set(i, n);
+                --i;
+            }
+            m_ncs.pop_back();
+        }
+    }
+    return m_new_propagation || ctx.inconsistent();
+}
 /*
    - Eqs = 0
    - Diseqs evaluate to false
@@ -762,20 +836,31 @@ void theory_seq::linearize(dependency* dep, enode_pair_vector& eqs, literal_vect
 
 
 void theory_seq::propagate_lit(dependency* dep, unsigned n, literal const* _lits, literal lit) {
+    if (lit == true_literal) return;
+
     context& ctx = get_context();
-    ctx.mark_as_relevant(lit);
     literal_vector lits(n, _lits);
+
+    if (lit == false_literal) {
+        set_conflict(dep, lits);
+        return;
+    }
+
+    ctx.mark_as_relevant(lit);
     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()); if (!lits.empty()) tout << "\n"; display_deps(tout, dep););
+    TRACE("seq",
+          tout << "assert:";
+          ctx.display_detailed_literal(tout, lit);
+          tout << " <- "; ctx.display_literals_verbose(tout, lits);
+          if (!lits.empty()) tout << "\n"; display_deps(tout, dep););
     justification* js =
         ctx.mk_justification(
             ext_theory_propagation_justification(
                 get_id(), ctx.get_region(), lits.size(), lits.c_ptr(), eqs.size(), eqs.c_ptr(), lit));
 
     m_new_propagation = true;
-    ctx.assign(lit, js);
+    ctx.assign(lit, js);    
 }
 
 void theory_seq::set_conflict(dependency* dep, literal_vector const& _lits) {
@@ -783,7 +868,7 @@ 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", display_deps(tout, lits, eqs););
+    TRACE("seq", display_deps(tout << "assert conflict:", lits, eqs););
     m_new_propagation = true;
     ctx.set_conflict(
         ctx.mk_justification(
@@ -800,7 +885,7 @@ 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) << " <- \n";
+          tout << "assert:" << mk_pp(n1->get_owner(), m) << " = " << mk_pp(n2->get_owner(), m) << " <- \n";
           display_deps(tout, dep);
           );
 
@@ -1484,6 +1569,30 @@ bool theory_seq::solve_ne(unsigned idx) {
     return updated;
 }
 
+bool theory_seq::solve_nc(unsigned idx) {
+    context& ctx = get_context();
+    nc const& n = m_ncs[idx];
+
+    dependency* deps = n.deps();    
+    expr_ref c = canonize(n.contains(), deps);
+
+    CTRACE("seq", c != n.contains(), tout << n.contains() << " => " << c << "\n";);
+    
+    if (m.is_true(c)) {
+        literal_vector lits;
+        set_conflict(deps, lits);
+        return true;
+    }
+    if (m.is_false(c)) {
+        return true;
+    }
+    if (c != n.contains()) {
+        m_ncs.push_back(nc(c, deps));
+        return true;
+    }
+    return false;
+}
+
 theory_seq::cell* theory_seq::mk_cell(cell* p, expr* e, dependency* d) {
     cell* c = alloc(cell, p, e, d);
     m_all_cells.push_back(c);
@@ -1747,6 +1856,20 @@ void theory_seq::display(std::ostream & out) const {
         out << "Exclusions:\n";
         m_exclude.display(out);
     }
+
+    if (!m_length.empty()) {
+        obj_hashtable<expr>::iterator it = m_length.begin(), end = m_length.end();
+        for (; it != end; ++it) {
+            expr* e = *it;
+            rational lo(-1), hi(-1);
+            lower_bound(e, lo);
+            upper_bound(e, hi);
+            if (lo.is_pos() || !hi.is_minus_one()) {
+                out << mk_pp(e, m) << " [" << lo << ":" << hi << "]\n";
+            }
+        }
+    }
+
 }
 
 void theory_seq::display_equations(std::ostream& out) const {
@@ -2360,7 +2483,7 @@ void theory_seq::propagate_in_re(expr* n, bool is_true) {
             propagate_lit(0, 1, &lit, lits[1]);
         }
         else {
-            TRACE("seq", ctx.display_literals_verbose(tout, lits.size(), lits.c_ptr()); tout << "\n";);
+            TRACE("seq", ctx.display_literals_verbose(tout, lits); tout << "\n";);
             ctx.mk_th_axiom(get_id(), lits.size(), lits.c_ptr());
         }
     }
@@ -2393,7 +2516,7 @@ static theory_mi_arith* get_th_arith(context& ctx, theory_id afid, expr* e) {
     }
 }
 
-bool theory_seq::lower_bound(expr* _e, rational& lo) {
+bool theory_seq::lower_bound(expr* _e, rational& lo) const {
     context& ctx = get_context();
     expr_ref e(m_util.str.mk_length(_e), m);
     theory_mi_arith* tha = get_th_arith(ctx, m_autil.get_family_id(), e);
@@ -2402,7 +2525,7 @@ bool theory_seq::lower_bound(expr* _e, rational& lo) {
     return m_autil.is_numeral(_lo, lo) && lo.is_int();
 }
 
-bool theory_seq::upper_bound(expr* _e, rational& hi) {
+bool theory_seq::upper_bound(expr* _e, rational& hi) const {
     context& ctx = get_context();
     expr_ref e(m_util.str.mk_length(_e), m);
     theory_mi_arith* tha = get_th_arith(ctx, m_autil.get_family_id(), e);
@@ -2411,7 +2534,7 @@ bool theory_seq::upper_bound(expr* _e, rational& hi) {
     return m_autil.is_numeral(_hi, hi) && hi.is_int();
 }
 
-bool theory_seq::get_length(expr* e, rational& val) {
+bool theory_seq::get_length(expr* e, rational& val) const {
     context& ctx = get_context();
     theory* th = ctx.get_theory(m_autil.get_family_id());
     if (!th) return false;
@@ -2705,7 +2828,6 @@ literal theory_seq::mk_eq_empty(expr* _e, bool phase) {
     literal lit = mk_eq(e, emp, false);
     ctx.force_phase(phase?lit:~lit);
     ctx.mark_as_relevant(lit);
-    TRACE("seq", tout << mk_pp(e, m) << " = empty\n";);
     return lit;
 }
 
@@ -2718,7 +2840,7 @@ void theory_seq::add_axiom(literal l1, literal l2, literal l3, literal l4, liter
     if (l3 != null_literal && l3 != false_literal) { ctx.mark_as_relevant(l3); lits.push_back(l3); }
     if (l4 != null_literal && l4 != false_literal) { ctx.mark_as_relevant(l4); lits.push_back(l4); }
     if (l5 != null_literal && l5 != false_literal) { ctx.mark_as_relevant(l5); lits.push_back(l5); }
-    TRACE("seq", ctx.display_literals_verbose(tout << "axiom: ", lits.size(), lits.c_ptr()); tout << "\n";);
+    TRACE("seq", ctx.display_literals_verbose(tout << "assert: ", lits); tout << "\n";);
     m_new_propagation = true;
     ++m_stats.m_add_axiom;
     ctx.mk_th_axiom(get_id(), lits.size(), lits.c_ptr());
@@ -2775,8 +2897,8 @@ void theory_seq::propagate_eq(dependency* deps, literal_vector const& _lits, exp
         new_eq_eh(deps, n1, n2);
     }
     TRACE("seq",
-          ctx.display_literals_verbose(tout, lits.size(), lits.c_ptr());
-          tout << " => " << mk_pp(e1, m) << " = " << mk_pp(e2, m) << "\n";);
+          tout << "assert: " << mk_pp(e1, m) << " = " << mk_pp(e2, m) << "<- \n";
+          ctx.display_literals_verbose(tout, lits););
     justification* js =
         ctx.mk_justification(
             ext_theory_eq_propagation_justification(
@@ -2848,10 +2970,15 @@ void theory_seq::assign_eh(bool_var v, bool is_true) {
         }
         else if (!canonizes(false, e)) {
             propagate_non_empty(lit, e2);
+#if 0
+            dependency* dep = m_dm.mk_leaf(assumption(lit));
+            m_ncs.push_back(nc(expr_ref(e, m), dep));
+#else
             propagate_lit(0, 1, &lit, ~mk_literal(m_util.str.mk_prefix(e2, e1)));
             if (add_contains2contains(e, change)) {
                 add_atom(e);
             }
+#endif
         }
     }
     else if (is_accept(e)) {
@@ -2921,7 +3048,7 @@ 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";);
+        TRACE("seq", tout << "new disequality " << get_context().get_scope_level() << ": " << eq << "\n";);
 
         literal lit = mk_eq(e1, e2, false);
 
@@ -2980,6 +3107,7 @@ void theory_seq::push_scope_eh() {
     m_trail_stack.push(value_trail<theory_seq, unsigned>(m_axioms_head));
     m_eqs.push_scope();
     m_nqs.push_scope();
+    m_ncs.push_scope();
     m_atoms_lim.push_back(m_atoms.size());
 }
 
@@ -2992,6 +3120,7 @@ void theory_seq::pop_scope_eh(unsigned num_scopes) {
     m_exclude.pop_scope(num_scopes);
     m_eqs.pop_scope(num_scopes);
     m_nqs.pop_scope(num_scopes);
+    m_ncs.pop_scope(num_scopes);
     m_atoms.resize(m_atoms_lim[m_atoms_lim.size()-num_scopes]);
     m_atoms_lim.shrink(m_atoms_lim.size()-num_scopes);
     m_rewrite.reset();    
@@ -3196,7 +3325,7 @@ bool theory_seq::add_accept2step(expr* acc, bool& change) {
     if (has_undef) {
         return true;
     }
-    TRACE("seq", ctx.display_literals_verbose(tout, lits.size(), lits.c_ptr()); tout << "\n";);
+    TRACE("seq", ctx.display_literals_verbose(tout, lits); tout << "\n";);
     for (unsigned i = 0; i < lits.size(); ++i) {
         SASSERT(ctx.get_assignment(lits[i]) == l_false);
         lits[i].neg();
@@ -3353,7 +3482,6 @@ void theory_seq::propagate_not_prefix(expr* e) {
 
 void theory_seq::propagate_not_prefix2(expr* e) {
     context& ctx = get_context();
-    //std::cout << mk_pp(e, m) << " " << ctx.get_scope_level() << "\n";
     expr* e1, *e2;
     VERIFY(m_util.str.is_prefix(e, e1, e2));
     literal lit = ctx.get_literal(e);
@@ -3423,7 +3551,7 @@ bool theory_seq::add_prefix2prefix(expr* e, bool& change) {
     switch (ctx.get_assignment(e2_is_emp)) {
     case l_true:
         TRACE("seq", tout << mk_pp(e, m) << ": " << mk_pp(e2, m) << " = empty\n";
-              ctx.display_literals_verbose(tout, 1, &e2_is_emp); tout << "\n"; );        
+              ctx.display_literal_verbose(tout, e2_is_emp); tout << "\n"; );        
         return false; // done
     case l_undef:
         // ctx.force_phase(e2_is_emp);
diff --git a/src/smt/theory_seq.h b/src/smt/theory_seq.h
index 23ab25905..c600e443f 100644
--- a/src/smt/theory_seq.h
+++ b/src/smt/theory_seq.h
@@ -191,6 +191,27 @@ namespace smt {
             expr_ref const& r() const { return m_r; }
         };
 
+        class nc {
+            expr_ref                 m_contains;
+            dependency*              m_dep;
+        public:
+            nc(expr_ref const& c, dependency* dep):
+                m_contains(c), 
+                m_dep(dep) {}
+            nc(nc const& other):
+                m_contains(other.m_contains), 
+                m_dep(other.m_dep) {}
+            nc& operator=(nc const& other) {
+                if (this != &other) {
+                    m_contains = other.m_contains;
+                    m_dep = other.m_dep;
+                }
+                return *this;
+            }
+            dependency* deps() const { return m_dep; }
+            expr_ref const& contains() const { return m_contains; }
+        };
+
         class apply {
         public:
             virtual ~apply() {}
@@ -263,12 +284,14 @@ namespace smt {
             unsigned m_add_axiom;
             unsigned m_extensionality;
             unsigned m_fixed_length;
+            unsigned m_propagate_contains;
         };
         ast_manager&               m;
         dependency_manager         m_dm;
         solution_map               m_rep;        // unification representative.
         scoped_vector<eq>          m_eqs;        // set of current equations.
         scoped_vector<ne>          m_nqs;        // set of current disequalities.
+        scoped_vector<nc>          m_ncs;        // set of non-contains constraints.
         unsigned                   m_eq_id;
 
         seq_factory*               m_factory;    // value factory
@@ -335,12 +358,14 @@ namespace smt {
         bool split_variable();           // split a variable
         bool is_solved(); 
         bool check_length_coherence();
+        bool check_length_coherence0(expr* e);
         bool check_length_coherence(expr* e);
         bool fixed_length();
         bool fixed_length(expr* e);
         bool propagate_length_coherence(expr* e);  
 
         bool check_extensionality();
+        bool check_contains();
         bool solve_eqs(unsigned start);
         bool solve_eq(expr_ref_vector const& l, expr_ref_vector const& r, dependency* dep);
         bool simplify_eq(expr_ref_vector& l, expr_ref_vector& r, dependency* dep);
@@ -362,6 +387,7 @@ namespace smt {
         expr_ref mk_concat(expr* e1, expr* e2, expr* e3) { return expr_ref(m_util.str.mk_concat(e1, e2, e3), m); }
         bool solve_nqs(unsigned i);
         bool solve_ne(unsigned i);
+        bool solve_nc(unsigned i);
 
         struct cell {
             cell*       m_parent;
@@ -452,9 +478,9 @@ namespace smt {
 
 
         // arithmetic integration
-        bool lower_bound(expr* s, rational& lo);
-        bool upper_bound(expr* s, rational& hi);
-        bool get_length(expr* s, rational& val);
+        bool lower_bound(expr* s, rational& lo) const;
+        bool upper_bound(expr* s, rational& hi) const;
+        bool get_length(expr* s, rational& val) const;
 
         void mk_decompose(expr* e, expr_ref& head, expr_ref& tail);
         expr_ref mk_skolem(symbol const& s, expr* e1, expr* e2 = 0, expr* e3 = 0, sort* range = 0);
@@ -494,7 +520,7 @@ namespace smt {
         void ensure_nth(literal lit, expr* s, expr* idx);
         bool canonizes(bool sign, expr* e);
         void propagate_non_empty(literal lit, expr* s);
-        void propagate_is_conc(expr* e, expr* conc);
+        bool propagate_is_conc(expr* e, expr* conc);
         void propagate_acc_rej_length(literal lit, expr* acc_rej);
         bool propagate_automata();
         void add_atom(expr* e);