Start adding vector types

src/lib.rs

@@ -0,0 +1,45 @@
+use std::ops::Add;
+
+#[derive(Clone, Copy)]
+struct Vector2D<T>(T,T);
+
+impl<T: Add> Add for Vector2D<T> {
+    type Output = Vector2D<T::Output>;
+
+    fn add(self, other: Vector2D<T>) -> Vector2D<T::Output> {
+        Vector2D(
+            self.0 + other.0,
+            self.1 + other.1,
+        )
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_add_zeroes_yields_zeroes() {
+        let a = Vector2D(0.0, 0.0);
+        let b = Vector2D(0.0, 0.0);
+        let c = a + b;
+        assert!(c.0 == 0.0);
+        assert!(c.0 == 0.0);
+    }
+
+    #[test]
+    fn test_addition_identity() {
+        let id = Vector2D(0.0, 0.0 );
+        let a = Vector2D(1.0, 2.0 );
+        {
+            let c = a + id;
+            assert!(c.0 == a.0);
+            assert!(c.1 == a.1);
+        }
+        {
+            let d = id + a;
+            assert!(d.0 == a.0);
+            assert!(d.1 == a.1);
+        }
+    }
+}