tuple addition and subtraction

tuples/src/lib.rs

@@ -41,6 +41,24 @@ fn tuple_equals(lhs: PointVector, rhs: PointVector) -> bool {
         && relative_eq!(lhs.3, rhs.3)
 }
 
+fn tuple_add(lhs: PointVector, rhs: PointVector) -> PointVector {
+    (
+        lhs.0 + rhs.0,
+        lhs.1 + rhs.1,
+        lhs.2 + rhs.2,
+        lhs.3 + rhs.3
+        )
+}
+
+fn tuple_sub(lhs: PointVector, rhs: PointVector) -> PointVector {
+    (
+        lhs.0 - rhs.0,
+        lhs.1 - rhs.1,
+        lhs.2 - rhs.2,
+        lhs.3 - rhs.3
+        )
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -99,4 +117,40 @@ mod tests {
         let rhs = vector(1.0, 2.0, 3.0);
         assert_eq!(false, tuple_equals(lhs, rhs));
     }
+
+    #[test]
+    fn add_two_tuples() {
+        let a1 = point(3.0, -2.0, 5.0);
+        let a2 = vector(-2.0, 3.0, 1.0);
+
+        let result = point(1.0, 1.0, 6.0);
+        assert_eq!(true, tuple_equals(result, tuple_add(a1, a2)));
+    }
+
+    #[test]
+    fn subtract_two_points() {
+        let a1 = point(3.0, 2.0, 1.0);
+        let a2 = point(5.0, 6.0, 7.0);
+
+        let result = vector(-2.0, -4.0, -6.0);
+        assert_eq!(true, tuple_equals(result, tuple_sub(a1, a2)));
+    }
+
+    #[test]
+    fn subract_vector_from_point() {
+        let a1 = point(3.0, 2.0, 1.0);
+        let a2 = vector(5.0, 6.0, 7.0);
+
+        let result = point(-2.0, -4.0, -6.0);
+        assert_eq!(true, tuple_equals(result, tuple_sub(a1, a2)));
+    }
+
+    #[test]
+    fn subract_vector_from_vector() {
+        let a1 = vector(3.0, 2.0, 1.0);
+        let a2 = vector(5.0, 6.0, 7.0);
+
+        let result = vector(-2.0, -4.0, -6.0);
+        assert_eq!(true, tuple_equals(result, tuple_sub(a1, a2)));
+    }
 }