@@ -0,0 +13,4 @@
+
+    /// R coordinate
+    pub r: i32,
+}

@@ -0,0 +53,4 @@
+        let dr = self.r - other.r;
+
+        // dz = |z1 - z2| where z = -q - r
+        let dz = self.q + self.r - other.q - other.r;

@@ -0,0 +105,4 @@
+
+impl<T: HexNumber> ops::AddAssign<Self> for HexPosition<T> {
+    fn add_assign(&mut self, other: Self) {
+        *self = *self + other;

@@ -0,0 +122,4 @@
+
+impl<T: HexNumber> ops::SubAssign<Self> for HexPosition<T> {
+    fn sub_assign(&mut self, other: Self) {
+        *self = *self - other;