Added better expressions

Advanced Software Engineering/Advanced Software Engineering/Verbs/Value/ValueTypes/ExpressionValue.cs

@@ -25,6 +25,36 @@ namespace Advanced_Software_Engineering.Verbs.Value {
             if (operation > 3 && operation < 0) throw new Exception("Bad operation");
         }
 
+        public ExpressionValue(Drawer drawer, IValue variable1, IValue variable2, string operation) {
+            switch(operation) {
+                case "+":
+                    this.operation = ADD;
+                    break;
+
+                case "-":
+                    this.operation = SUBTRACT;
+                    break;
+
+                case "*":
+                    this.operation = MULTIPLY;
+                    break;
+
+                case "/":
+                    this.operation = DIVIDE;
+                    break;
+
+                default:
+                    throw new Exception("Undefined operation");
+            }
+
+            this.variable1 = variable1;
+            this.variable2 = variable2;
+            
+
+            //Check for bad input
+            if (this.operation > 3 && this.operation < 0) throw new Exception("Bad operation");
+        }
+
         private IValue Evaluate() {
             if (evaluated) return evaluatedValue;