multiplicaiton, division, and negation

tuples/src/lib.rs

@@ -59,6 +59,33 @@ fn tuple_sub(lhs: PointVector, rhs: PointVector) -> PointVector {
         )
 }
 
+fn tuple_neg(lhs: PointVector) -> PointVector {
+    (
+        -lhs.0,
+        -lhs.1,
+        -lhs.2,
+        -lhs.3
+        )
+}
+
+fn tuple_mult(lhs: PointVector, scalar: f32) -> PointVector {
+    (
+        lhs.0 * scalar,
+        lhs.1 * scalar,
+        lhs.2 * scalar,
+        lhs.3 * scalar,
+        )
+}
+
+fn tuple_div(lhs: PointVector, divisor: f32) -> PointVector {
+    (
+        lhs.0 / divisor,
+        lhs.1 / divisor,
+        lhs.2 / divisor,
+        lhs.3 / divisor,
+        )
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -153,4 +180,45 @@ mod tests {
         let result = vector(-2.0, -4.0, -6.0);
         assert_eq!(true, tuple_equals(result, tuple_sub(a1, a2)));
     }
+
+    #[test]
+    fn subtract_vector_from_zero_vector() {
+        let a1 = vector(0.0, 0.0, 0.0);
+        let a2 = vector(5.0, 6.0, 7.0);
+
+        let result = vector(-5.0, -6.0, -7.0);
+        assert_eq!(true, tuple_equals(result, tuple_sub(a1, a2)));
+    }
+
+    #[test]
+    fn negate_tuple() {
+        let a = (1.0, -2.0, 3.0, -4.0);
+        let result = (-1.0, 2.0, -3.0, 4.0);
+
+        assert_eq!(result, tuple_neg(a));
+    }
+
+    #[test]
+    fn multiply_tuple_by_scalar() {
+        let a = (1.0, -2.0, 3.0, -4.0);
+        let result = (3.5, -7.0, 10.5, -14.0);
+
+        assert_eq!(true, tuple_equals(result, tuple_mult(a, 3.5)));
+    }
+
+    #[test]
+    fn multiply_tuple_by_fraction() {
+        let a = (1.0, -2.0, 3.0, -4.0);
+        let result = (0.5, -1.0, 1.5, -2.0);
+
+        assert_eq!(true, tuple_equals(result, tuple_mult(a, 0.5)));
+    }
+
+    #[test]
+    fn divide_tuple() {
+        let a = (1.0, -2.0, 3.0, -4.0);
+        let result = (0.5, -1.0, 1.5, -2.0);
+
+        assert_eq!(true, tuple_equals(result, tuple_div(a, 2.0)));
+    }
 }