add string accessors to managed APIs #1051

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

src/api/dotnet/Expr.cs

@@ -797,6 +797,22 @@ namespace Microsoft.Z3
         public bool IsLabelLit { get { return IsApp && FuncDecl.DeclKind == Z3_decl_kind.Z3_OP_LABEL_LIT; } }
         #endregion
 
+        #region Sequences and Strings
+
+        /// <summary>
+        /// Check whether expression is a string constant.
+        /// </summary>
+        /// <returns>a Boolean</returns>
+        public bool IsString  { get { return IsApp && 0 != Native.Z3_is_string(Context.nCtx, NativeObject); } }
+
+        /// <summary>
+        /// Retrieve string corresponding to string constant.
+        /// </summary>
+        /// <remarks>the expression should be a string constant, (IsString should be true).</remarks>
+        public string String { get { return Native.Z3_get_string(Context.nCtx, NativeObject); } }        
+
+        #endregion
+
         #region Proof Terms
         /// <summary>
         /// Indicates whether the term is a binary equivalence modulo namings.

src/api/java/Expr.java

@@ -1277,6 +1277,26 @@ public class Expr extends AST
         return isApp() && getFuncDecl().getDeclKind() == Z3_decl_kind.Z3_OP_LABEL_LIT;
     }
 
+    /**
+     * Check whether expression is a string constant.
+     * @return a boolean
+     */
+    public boolean isString() 
+    {
+        return isApp() && Native.isString(getContext().nCtx(), getNativeObject());
+    }
+
+    /**
+     * Retrieve string corresponding to string constant.
+     * Remark: the expression should be a string constant, (isString() should return true).
+     * @throws Z3Exception on error
+     * @return a string
+     */
+    public String getString()
+    {
+	return Native.getString(getContext().nCtx(), getNativeObject());
+    }
+
     /**
      * Indicates whether the term is a binary equivalence modulo namings.
      * Remarks: This binary predicate is used in proof terms. It captures