Includes division by zero error.

src/interpreter/interpreter.rs

@@ -101,13 +101,17 @@ fn mul(lhs: Expression, rhs: Expression, env: &Environment) -> Result<Expression
 }
 
 fn div(lhs: Expression, rhs: Expression, env: &Environment) -> Result<Expression, ErrorMessage> {
-    eval_binary_arith_op(
-        lhs,
-        rhs,
-        env,
-        |a, b| a / b,
-        "division '(/)' is only defined for numbers (integers and real).",
-    )
+    match eval(rhs.clone(), env)? {
+        Expression::CInt(0) => Err(String::from("division by zero is undefined.")),
+        Expression::CReal(0.0) => Err(String::from("division by zero is undefined.")),
+        _ => eval_binary_arith_op(
+            lhs,
+            rhs,
+            env,
+            |a, b| a / b,
+            "division '(/)' is only defined for numbers (integers and real).",
+        ),
+    }
 }
 
 /* Boolean Expressions */
@@ -186,6 +190,7 @@ where
 {
     let v1 = eval(lhs, env)?;
     let v2 = eval(rhs, env)?;
+
     match (v1, v2) {
         (Expression::CInt(v1), Expression::CInt(v2)) => Ok(op(v1 as f64, v2 as f64)),
         (Expression::CInt(v1), Expression::CReal(v2)) => Ok(op(v1 as f64, v2)),
@@ -440,6 +445,58 @@ mod tests {
         }
     }
 
+    #[test]
+    fn eval_div_expression5_division_by_zero() {
+        let env = HashMap::new();
+        let c10 = CReal(10.0);
+        let c0 = CReal(0.0);
+        let div1 = Div(Box::new(c10), Box::new(c0));
+
+        assert_eq!(
+            eval(div1, &env),
+            Err(String::from("division by zero is undefined."))
+        );
+    }
+
+    #[test]
+    fn eval_div_expression6_division_by_zero() {
+        let env = HashMap::new();
+        let c10 = CInt(10);
+        let c0 = CReal(0.0);
+        let div1 = Div(Box::new(c10), Box::new(c0));
+
+        assert_eq!(
+            eval(div1, &env),
+            Err(String::from("division by zero is undefined."))
+        );
+    }
+
+    #[test]
+    fn eval_div_expression7_division_by_zero() {
+        let env = HashMap::new();
+        let c10 = CReal(10.0);
+        let c0 = CInt(0);
+        let div1 = Div(Box::new(c10), Box::new(c0));
+
+        assert_eq!(
+            eval(div1, &env),
+            Err(String::from("division by zero is undefined."))
+        );
+    }
+
+    #[test]
+    fn eval_div_expression8_division_by_zero() {
+        let env = HashMap::new();
+        let c10 = CInt(10);
+        let c0 = CInt(0);
+        let div1 = Div(Box::new(c10), Box::new(c0));
+
+        assert_eq!(
+            eval(div1, &env),
+            Err(String::from("division by zero is undefined."))
+        );
+    }
+
     #[test]
     fn eval_variable() {
         let env = HashMap::from([(String::from("x"), CInt(10)), (String::from("y"), CInt(20))]);