Implement operator overloads for Angle type

src/angle.rs

@@ -22,6 +22,66 @@ pub impl<T:Copy Num NumCast> Angle<T> {
     }
 }
 
+pub impl<T:Copy Num> Angle<T>: Add<T,Angle<T>> {
+    #[inline(always)]
+    pure fn add(rhs: &T) -> Angle<T> {
+        match self {
+            degrees(theta) => degrees(theta + *rhs),
+            radians(theta) => radians(theta + *rhs)
+        }
+    }
+}
+
+pub impl<T:Copy Num> Angle<T>: Sub<T,Angle<T>> {
+    #[inline(always)]
+    pure fn sub(rhs: &T) -> Angle<T> {
+        match self {
+            degrees(theta) => degrees(theta - *rhs),
+            radians(theta) => radians(theta - *rhs)
+        }
+    }
+}
+
+pub impl<T:Copy Num> Angle<T>: Mul<T,Angle<T>> {
+    #[inline(always)]
+    pure fn mul(rhs: &T) -> Angle<T> {
+        match self {
+            degrees(theta) => degrees(theta * *rhs),
+            radians(theta) => radians(theta * *rhs)
+        }
+    }
+}
+
+pub impl<T:Copy Num> Angle<T>: Div<T,Angle<T>> {
+    #[inline(always)]
+    pure fn div(rhs: &T) -> Angle<T> {
+        match self {
+            degrees(theta) => degrees(theta / *rhs),
+            radians(theta) => radians(theta / *rhs)
+        }
+    }
+}
+
+pub impl<T:Copy Num> Angle<T>: Modulo<T,Angle<T>> {
+    #[inline(always)]
+    pure fn modulo(rhs: &T) -> Angle<T> {
+        match self {
+            degrees(theta) => degrees(theta % *rhs),
+            radians(theta) => radians(theta % *rhs)
+        }
+    }
+}
+
+pub impl<T:Copy Num> Angle<T>: Neg<Angle<T>> {
+    #[inline(always)]
+    pure fn neg() -> Angle<T> {
+        match self {
+            degrees(theta) => degrees(-theta),
+            radians(theta) => radians(-theta)
+        }
+    }
+}
+
 pub struct AxisRotation<T> {
     axis: Vec3<T>,
     theta: Angle<T>,