fix(deep_causality_num): Minor fixes and lints.

Signed-off-by: Marvin Hansen <[email protected]>

Author: marvin-hansen

deep_causality_num/src/quaternion/arithmetic.rs

@@ -97,11 +97,14 @@ impl<F: Float> Mul for Quaternion<F> {
     /// assert_eq!(q_j * q_i, -q_k); // j * i = -k
     /// ```
     fn mul(self, other: Self) -> Self {
+        let (w1, x1, y1, z1) = (self.w, self.x, self.y, self.z);
+        let (w2, x2, y2, z2) = (other.w, other.x, other.y, other.z);
+
         Quaternion {
-            w: self.w * other.w - self.x * other.x - self.y * other.y - self.z * other.z,
-            x: self.w * other.x + self.x * other.w + self.y * other.z - self.z * other.y,
-            y: self.w * other.y - self.x * other.z + self.y * other.w + self.z * other.x,
-            z: self.w * other.z + self.x * other.y - self.y * other.x + self.z * other.w,
+            w: w1 * w2 - x1 * x2 - y1 * y2 - z1 * z2,
+            x: w1 * x2 + x1 * w2 + y1 * z2 - z1 * y2,
+            y: w1 * y2 - x1 * z2 + y1 * w2 + z1 * x2,
+            z: w1 * z2 + x1 * y2 - y1 * x2 + z1 * w2,
         }
     }
 }

deep_causality_num/tests/quaternion/as_primitive_tests.rs

@@ -5,14 +5,14 @@ use deep_causality_num::Quaternion;
 fn test_as_primitive_f64() {
     let q = Quaternion::new(1.23, 4.56, 7.89, 0.12);
     let val: f64 = q.as_();
-    assert_eq!(val, 1.23);
+    assert!((val - 1.23).abs() < 1e-12);
 }
 
 #[test]
 fn test_as_primitive_f32() {
     let q = Quaternion::new(1.23f32, 4.56f32, 7.89f32, 0.12f32);
     let val: f32 = q.as_();
-    assert_eq!(val, 1.23f32);
+    assert!((val - 1.23f32).abs() < 1e-6);
 }
 
 #[test]

deep_causality_num/tests/quaternion/display_tests.rs

@@ -5,4 +5,8 @@ fn test_display_format() {
     let q = Quaternion::new(1.0, 2.0, 3.0, 4.0);
     let display_str = format!("{}", q);
     assert_eq!(display_str, "1 + 2i + 3j + 4k");
+
+    let q_neg = Quaternion::new(1.0, -2.0, 3.0, -4.0);
+    let display_str_neg = format!("{}", q_neg);
+    assert_eq!(display_str_neg, "1 - 2i + 3j - 4k");
 }