fix examples and C++ API - build failure

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

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

@@ -1111,10 +1111,10 @@ namespace z3 {
     }
 
     inline expr concat(expr const& a, expr const& b) {
-        context& ctx = a.ctx();
+        check_context(a, b);
-        Z3_ast r = Z3_mk_concat(ctx, (Z3_ast) a, (Z3_ast) b);
+        Z3_ast r = Z3_mk_concat(a.ctx(), a, b);
-        ctx.check_error();
+        a.ctx().check_error();
-        return expr(ctx, r);
+        return expr(a.ctx(), r);
     }
     
     class func_entry : public object {

src/api/java/InterpolationContext.java

@@ -87,6 +87,13 @@ public class InterpolationContext extends Context
         return res;
     }
 
+    public class ComputeInterpolantResult 
+    {
+        public Z3_lbool status = Z3_lbool.Z3_L_UNDEF;
+        public ASTVector interp = null;
+        public Model model = null;
+    };
+    
     /**
      * Computes an interpolant.   
      * Remarks: For more information on interpolation please refer
@@ -94,17 +101,18 @@ public class InterpolationContext extends Context
      * well documented.
      * @throws Z3Exception 
      **/
-    public Z3_lbool ComputeInterpolant(Expr pat, Params p, ASTVector interp, Model model)
+    public ComputeInterpolantResult ComputeInterpolant(Expr pat, Params p)
     {
         checkContextMatch(pat);
         checkContextMatch(p);
 
+        ComputeInterpolantResult res = new ComputeInterpolantResult();
         Native.LongPtr n_i = new Native.LongPtr();
         Native.LongPtr n_m = new Native.LongPtr();
-        int r = Native.computeInterpolant(nCtx(), pat.getNativeObject(), p.getNativeObject(), n_i, n_m);
+        res.status =Z3_lbool.fromInt(Native.computeInterpolant(nCtx(), pat.getNativeObject(), p.getNativeObject(), n_i, n_m));        
-        interp = new ASTVector(this, n_i.value);
+        if (res.status == Z3_lbool.Z3_L_FALSE) res.interp = new ASTVector(this, n_i.value);
-        model = new Model(this, n_m.value);
+        if (res.status == Z3_lbool.Z3_L_TRUE) res.model = new Model(this, n_m.value);
-        return Z3_lbool.fromInt(r);
+        return res;
     }
 
     ///  
@@ -118,16 +126,23 @@ public class InterpolationContext extends Context
         return Native.interpolationProfile(nCtx());
     }
 
+    public class CheckInterpolantResult
+    {
+        public int return_value = 0;
+        public String error = null;
+    }
+    
     ///  
     /// Checks the correctness of an interpolant.
     ///    
     /// Remarks: For more information on interpolation please refer
     /// too the function Z3_check_interpolant in the C/C++ API, which is 
     /// well documented.
-    public int CheckInterpolant(Expr[] cnsts, int[] parents, Expr[] interps, String error, Expr[] theory)
+    public CheckInterpolantResult CheckInterpolant(Expr[] cnsts, int[] parents, Expr[] interps, String error, Expr[] theory)
     {
+        CheckInterpolantResult res = new CheckInterpolantResult();
         Native.StringPtr n_err_str = new Native.StringPtr();
-        int r = Native.checkInterpolant(nCtx(),
+        res.return_value = Native.checkInterpolant(nCtx(),
                                         cnsts.length,
                                         Expr.arrayToNative(cnsts),
                                         parents,
@@ -135,41 +150,52 @@ public class InterpolationContext extends Context
                                         n_err_str,
                                         theory.length,
                                         Expr.arrayToNative(theory));
-        error = n_err_str.value;
+        res.error = n_err_str.value;
-        return r;
+        return res;
     }
 
+    public class ReadInterpolationProblemResult 
+    {
+        public int return_value = 0;
+        public Expr[] cnsts;
+        public int[] parents;
+        public String error;
+        public Expr[] theory;
+    };
+    
     ///  
     /// Reads an interpolation problem from a file.
     ///    
     /// Remarks: For more information on interpolation please refer
     /// too the function Z3_read_interpolation_problem in the C/C++ API, which is 
     /// well documented.
-    public int ReadInterpolationProblem(String filename, Expr[] cnsts, int[] parents, String error, Expr[] theory)
+    public ReadInterpolationProblemResult ReadInterpolationProblem(String filename, Expr[] cnsts, int[] parents, String error, Expr[] theory)
     {
+        ReadInterpolationProblemResult res = new ReadInterpolationProblemResult();
+        
         Native.IntPtr n_num = new Native.IntPtr();
         Native.IntPtr n_num_theory = new Native.IntPtr();
         Native.ObjArrayPtr n_cnsts = new Native.ObjArrayPtr();
         Native.UIntArrayPtr n_parents = new Native.UIntArrayPtr();
         Native.ObjArrayPtr n_theory = new Native.ObjArrayPtr();
         Native.StringPtr n_err_str = new Native.StringPtr();
-        int r = Native.readInterpolationProblem(nCtx(), n_num, n_cnsts, n_parents, filename, n_err_str, n_num_theory, n_theory);
+        res.return_value = Native.readInterpolationProblem(nCtx(), n_num, n_cnsts, n_parents, filename, n_err_str, n_num_theory, n_theory);
         int num = n_num.value;
         int num_theory = n_num_theory.value;
-        error = n_err_str.value;
+        res.error = n_err_str.value;
-        cnsts = new Expr[num];
+        res.cnsts = new Expr[num];
-        parents = new int[num];
+        res.parents = new int[num];
         theory = new Expr[num_theory];
         for (int i = 0; i < num; i++)
         {
-            cnsts[i] = Expr.create(this, n_cnsts.value[i]);
+            res.cnsts[i] = Expr.create(this, n_cnsts.value[i]);
-            parents[i] = n_parents.value[i];
+            res.parents[i] = n_parents.value[i];
         }
         for (int i = 0; i < num_theory; i++)
-            theory[i] = Expr.create(this, n_theory.value[i]);
+            res.theory[i] = Expr.create(this, n_theory.value[i]);
-        return r;
+        return res;
     }
-
+    
     ///  
     /// Writes an interpolation problem to a file.
     ///