add operator conversion for efficient parallelizing

inc/expression.hpp

@@ -110,6 +110,12 @@ public:
 		case OPERATOR:
 			v.o = other.v.o;
 			break;
+		case CV:
+			v.cv.w = other.v.cv.w;
+			v.cv.i = other.v.cv.i;
+			break;
+		case NAT:
+			break;
 		default:
 			std::cout << "Warning: token type is invalid\n";
 			break;
@@ -131,12 +137,47 @@ public:
 		case OPERATOR:
 			v.o = other.v.o;
 			break;
+		case CV:
+			v.cv.w = other.v.cv.w;
+			v.cv.i = other.v.cv.i;
+			break;
+		case NAT:
+			break;
 		default:
 			std::cout << "Warning: token type is invalid\n";
 			break;
 		}
 	}
 
+	Expression::Token& operator=(const Expression::Token& other)
+	{
+		t = other.t;
+
+		switch (t)
+		{
+		case VAR:
+			v.s = other.v.s;
+			break;
+		case CONST:
+			v.d = other.v.d;
+			break;
+		case OPERATOR:
+			v.o = other.v.o;
+			break;
+		case CV:
+			v.cv.w = other.v.cv.w;
+			v.cv.i = other.v.cv.i;
+			break;
+		case NAT:
+			break;
+		default:
+			std::cout << "Warning: token type is invalid\n";
+			break;
+		}
+
+		return const_cast<Expression::Token&>(other);
+	}
+
 	std::shared_ptr<std::string> to_str(void) const
 	{
 		switch (t)