add backtrack level to cuber interface

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/solver/combined_solver.cpp

@@ -281,8 +281,8 @@ public:
         return m_solver1->get_num_assumptions() + m_solver2->get_num_assumptions();
     }
 
-    virtual expr_ref cube() {
-        return m_solver1->cube();
+    virtual expr_ref cube(unsigned backtrack_level) {
+        return m_solver1->cube(backtrack_level);
     }
 
     virtual expr * get_assumption(unsigned idx) const {

src/solver/solver.h

@@ -189,7 +189,7 @@ public:
        \brief extract a lookahead candidates for branching.
     */
 
-    virtual expr_ref cube() = 0;
+    virtual expr_ref cube(unsigned backtrack_level) = 0;
 
     /**
        \brief Display the content of this solver.

src/solver/solver_pool.cpp

@@ -223,7 +223,7 @@ public:
     virtual void get_labels(svector<symbol> & r) { return m_base->get_labels(r); }
     virtual void set_progress_callback(progress_callback * callback) { m_base->set_progress_callback(callback); }
 
-    virtual expr_ref cube() { return expr_ref(m.mk_true(), m); }
+    virtual expr_ref cube(unsigned ) { return expr_ref(m.mk_true(), m); }
 
     virtual ast_manager& get_manager() const { return m_base->get_manager(); } 
 

src/solver/tactic2solver.cpp

@@ -77,7 +77,7 @@ public:
 
     virtual ast_manager& get_manager() const; 
 
-    virtual expr_ref cube() {
+    virtual expr_ref cube(unsigned ) {
         ast_manager& m = get_manager();
         return expr_ref(m.mk_true(), m);
     }