Add Degrees and Radians as newtypes

diff --git a/src/common.rs b/src/common.rs
index c75274c..2be427e 100644 (file)
--- a/src/common.rs
+++ b/src/common.rs
@@ -116,6 +116,41 @@ impl<T> From<(T, T)> for Point2D<T> {
     }
 }
 
+impl From<Degrees> for Point2D<f64> {
+    fn from(item: Degrees) -> Self {
+        Point2D {
+            x: (item.0 * std::f64::consts::PI / 180.0).cos(),
+            y: (item.0 * std::f64::consts::PI / 180.0).sin(),
+        }
+    }
+}
+
+impl From<Radians> for Point2D<f64> {
+    fn from(item: Radians) -> Self {
+        Point2D {
+            x: item.0.cos(),
+            y: item.0.sin(),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Clone, Copy)]
+struct Degrees(f64);
+#[derive(Debug, PartialEq, Clone, Copy)]
+struct Radians(f64);
+
+impl Degrees {
+    fn to_radians(&self) -> Radians {
+       Radians(self.0 * std::f64::consts::PI / 180.0)
+    }
+}
+
+impl Radians {
+    fn to_degrees(&self) -> Degrees {
+       Degrees(self.0 * 180.0 * std::f64::consts::FRAC_1_PI)
+    }
+}
+
 #[macro_export]
 macro_rules! rect {
     ( $x:expr, $y:expr ) => {
@@ -206,6 +241,15 @@ mod tests {
     }
 
     #[test]
+    fn angles() {
+       assert_eq!(Radians(0.0).to_degrees(), Degrees(0.0));
+       assert_eq!(Radians(std::f64::consts::PI).to_degrees(), Degrees(180.0));
+       assert_eq!(Degrees(180.0).to_radians(), Radians(std::f64::consts::PI));
+       assert!((Point2D::from(Degrees(90.0)) - point!(0.0, 1.0)).length() < 0.001);
+       assert!((Point2D::from(Radians(std::f64::consts::FRAC_PI_2)) - point!(0.0, 1.0)).length() < 0.001);
+    }
+
+    #[test]
     fn area_for_rect_of_multipliable_type() {
         let r: Rect<_> = (30, 20).into(); // the Into trait uses the From trait
         assert_eq!(r.area(), 30 * 20);