Added bit2bool to the API (#5992)

* Fixed registering expressions in push/pop

* Reused existing function

* Reverted reusing can_propagate

* Added decide-callback to user-propagator

* Refactoring

* Fixed index

* Added bit2bool to the API
Fixed bug in user-propagator's decide callback

* Fixed typo

src/api/api_bv.cpp

@@ -102,6 +102,7 @@ Z3_ast Z3_API NAME(Z3_context c, unsigned i, Z3_ast n) {                \
     MK_BV_PUNARY(Z3_mk_sign_ext, OP_SIGN_EXT);
     MK_BV_PUNARY(Z3_mk_zero_ext, OP_ZERO_EXT);
     MK_BV_PUNARY(Z3_mk_repeat,   OP_REPEAT);
+    MK_BV_PUNARY(Z3_mk_bit2bool,   OP_BIT2BOOL);
     MK_BV_PUNARY(Z3_mk_rotate_left, OP_ROTATE_LEFT);
     MK_BV_PUNARY(Z3_mk_rotate_right, OP_ROTATE_RIGHT);
     MK_BV_PUNARY(Z3_mk_int2bv, OP_INT2BV);

src/api/c++/z3++.h

@@ -1359,6 +1359,7 @@ namespace z3 {
 
         friend expr operator~(expr const & a);
         expr extract(unsigned hi, unsigned lo) const { Z3_ast r = Z3_mk_extract(ctx(), hi, lo, *this); ctx().check_error(); return expr(ctx(), r); }
+        expr bit2bool(unsigned i) const { Z3_ast r = Z3_mk_bit2bool(ctx(), i, *this); ctx().check_error(); return expr(ctx(), r); }
         unsigned lo() const { assert (is_app() && Z3_get_decl_num_parameters(ctx(), decl()) == 2); return static_cast<unsigned>(Z3_get_decl_int_parameter(ctx(), decl(), 1)); }
         unsigned hi() const { assert (is_app() && Z3_get_decl_num_parameters(ctx(), decl()) == 2); return static_cast<unsigned>(Z3_get_decl_int_parameter(ctx(), decl(), 0)); }
 

src/api/z3_api.h

@@ -2914,6 +2914,16 @@ extern "C" {
        def_API('Z3_mk_repeat', AST, (_in(CONTEXT), _in(UINT), _in(AST)))
     */
     Z3_ast Z3_API Z3_mk_repeat(Z3_context c, unsigned i, Z3_ast t1);
+    
+    /**
+       \brief Extracts the bit at position \ccode{i} of a bit-vector and 
+       yields a boolean.
+
+       The node \c t1 must have a bit-vector sort.
+
+       def_API('Z3_mk_bit2bool', AST, (_in(CONTEXT), _in(UINT), _in(AST)))
+    */
+    Z3_ast Z3_API Z3_mk_bit2bool(Z3_context c, unsigned i, Z3_ast t1);
 
     /**
        \brief Shift left.
@@ -6755,16 +6765,16 @@ extern "C" {
     void Z3_API Z3_solver_propagate_diseq(Z3_context c, Z3_solver s, Z3_eq_eh eq_eh);
 
     /**
-    * \brief register a callback when a new expression with a registered function is used by the solver 
-    * The registered function appears at the top level and is created using \ref Z3_propagate_solver_declare.
+       \brief register a callback when a new expression with a registered function is used by the solver 
+       The registered function appears at the top level and is created using \ref Z3_propagate_solver_declare.
     */
     void Z3_API Z3_solver_propagate_created(Z3_context c, Z3_solver s, Z3_created_eh created_eh);
     
     /**
-    * \brief register a callback when a the solver decides to split on a registered expression 
-    * The callback may set passed expression to another registered expression which will be selected instead.
-    * In case the expression is a bitvector the bit to split on is determined by the bit argument and the 
-    * truth-value to try first is given by is_pos
+       \brief register a callback when the solver decides to split on a registered expression.
+       The callback may set the passed expression to another registered expression which will be selected instead.
+       In case the expression is a bitvector the bit to split on is determined by the bit argument and the 
+       truth-value to try first is given by is_pos. In case the truth value is undefined the solver will decide.
     */
     void Z3_API Z3_solver_propagate_decide(Z3_context c, Z3_solver s, Z3_decide_eh decide_eh);
 

src/smt/theory_bv.cpp

@@ -1842,11 +1842,11 @@ namespace smt {
         unsigned sz = bits.size();
 
         for (unsigned i = start_bit; i < sz; ++i) {
-            if (ctx.get_assignment(bits[i].var()) != l_undef)
+            if (ctx.get_assignment(bits[i].var()) == l_undef)
                 return bits[i].var();
         }
         for (unsigned i = 0; i < start_bit; ++i) {
-            if (ctx.get_assignment(bits[i].var()) != l_undef)
+            if (ctx.get_assignment(bits[i].var()) == l_undef)
                 return bits[i].var();
         }
 

src/smt/theory_user_propagator.cpp

@@ -159,37 +159,53 @@ void theory_user_propagator::new_fixed_eh(theory_var v, expr* value, unsigned nu
 void theory_user_propagator::decide(bool_var& var, bool& is_pos) {
 
     const bool_var_data& d = ctx.get_bdata(var);
-
-    if (!d.is_theory_atom())
+    
+    if (!d.is_enode() && !d.is_theory_atom()) 
         return;
-
-    theory* th = ctx.get_theory(d.get_theory());
-
-    bv_util bv(m);
-    enode* original_enode = nullptr;
+    
+    enode* original_enode = nullptr; 
     unsigned original_bit = 0;
-
-    if (d.is_enode() && th->get_family_id() == get_family_id()) {
-        // variable is just a registered expression
+    bv_util bv(m);
+    theory* th = nullptr;
+    theory_var v = null_theory_var;
+    
+    // get the associated theory
+    if (!d.is_enode()) {
+        // it might be a value that does not have an enode
+        th = ctx.get_theory(d.get_theory());
+    }
+    else {
         original_enode = ctx.bool_var2enode(var);
+        v = original_enode->get_th_var(get_family_id());
+        if (v == null_theory_var) {
+            // it is not a registered boolean expression
+            th = ctx.get_theory(d.get_theory());
+        }
     }
-    else if (th->get_family_id() == bv.get_fid()) {
-        // it might be a registered bit-vector
-        auto registered_bv = ((theory_bv*)th)->get_bv_with_theory(var, get_family_id());
-        if (!registered_bv.first)
-            // there is no registered bv associated with the bit
-            return;
-        original_enode = registered_bv.first;
-        original_bit = registered_bv.second;
-    }
-    else
+    
+    if (!th && v == null_theory_var)
         return;
 
+    if (v == null_theory_var) {
+        if (th->get_family_id() == bv.get_fid()) {
+            // it is not a registered boolean value but it is a bitvector
+            auto registered_bv = ((theory_bv*)th)->get_bv_with_theory(var, get_family_id());
+            if (!registered_bv.first)
+                // there is no registered bv associated with the bit
+                return;
+            original_enode = registered_bv.first;
+            original_bit = registered_bv.second;
+            v = original_enode->get_th_var(get_family_id());
+        }
+        else
+            return;
+    }
+
     // call the registered callback
     unsigned new_bit = original_bit;
     lbool phase = is_pos ? l_true : l_false;
-
-    expr* e = var2expr(original_enode->get_th_var(get_family_id()));
+    
+    expr* e = var2expr(v);
     m_decide_eh(m_user_context, this, &e, &new_bit, &phase);
     enode* new_enode = ctx.get_enode(e);
 
@@ -201,7 +217,6 @@ void theory_user_propagator::decide(bool_var& var, bool& is_pos) {
         return;
     }
 
-    bool_var old_var = var;
     if (new_enode->is_bool()) {
         // expression was set to a boolean
         bool_var new_var = ctx.enode2bool_var(new_enode);