Added trait Rateable.

src/lib.rs

@@ -10,6 +10,24 @@ fn expected(a: f32, b: f32, n: f32) -> f32 {
     1.0 / (1.0 + 10.0_f32.powf((b - a) / n))
 }
 
+trait Rateable {
+    fn rating(&mut self) -> &mut f32;
+
+    fn record_match(&mut self, other: &mut Self, score: f32) {
+        let r_a = *self.rating();
+        let r_b = *other.rating();
+
+        *self.rating() = rating(r_a, r_b, score, 400.0, 32.0);
+        *other.rating() = rating(r_b, r_a, 1.0 - score, 400.0, 32.0);
+    }
+}
+
+impl Rateable for f32 {
+    fn rating(&mut self) -> &mut f32 {
+        self
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -24,4 +42,14 @@ mod tests {
 
         assert_eq!(r, 1600.0);
     }
+
+    #[test]
+    fn test_rateable() {
+        let mut a: f32 = 1600.0;
+        let mut b: f32 = 1600.0;
+
+        a.record_match(&mut b, 1.0);
+
+        assert_eq!(a, 1616.0);
+    }
 }