Add angle calculation logic for D10

2019/10/src/main.rs

@@ -1,3 +1,24 @@
 fn main() {
     println!("Hello, world!");
 }
+
+fn calculate_angle(x_offset: i32, y_offset: i32) -> f32 {
+    return ((y_offset as f32).atan2(x_offset as f32).to_degrees() * 1000.0).round();
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_angle_calculation() {
+        assert_eq!(calculate_angle(1, 1), 45_000.0);
+        assert_eq!(calculate_angle(1, 0), 0.0);
+        assert_eq!(calculate_angle(0, -1), -90_000.0);
+        assert_eq!(calculate_angle(2, 1), 26_565.0);
+        assert_eq!(calculate_angle(1, 1), calculate_angle(3, 3));
+        assert_eq!(calculate_angle(-2, -2), -135_000.0);
+        assert_eq!(calculate_angle(-2, 2), 135_000.0);
+        assert_ne!(calculate_angle(1, 1), calculate_angle(3, -3));
+    }
+}