Cleaned up eval error messages

src/evaluate/mod.rs

@@ -11,4 +11,27 @@ pub enum EvalError {
 	ZeroDivision,
 	IncompatibleUnit,
 	BadDefineName
-}
+}
+
+
+impl ToString for EvalError {
+	fn to_string(&self) -> String {
+		match self {
+			EvalError::BadMath => {
+				String::from("Failed to evaluate expression")
+			},
+			EvalError::TooBig => {
+				String::from("Number too big")
+			},
+			EvalError::ZeroDivision => {
+				String::from("Division by zero")
+			},
+			EvalError::IncompatibleUnit => {
+				String::from("Incompatible units")
+			},
+			EvalError::BadDefineName => {
+				String::from("Invalid variable name")
+			}
+		}
+	}
+}