convert forward into a method

src/main.rs

@@ -20,10 +20,12 @@ mod rover {
 	}
     }
 
-    pub fn forward(slf : &Rover) -> Rover {
-	let Rover(lon, lat, direction) = slf;
-	let (xoff, yoff) = velocity(&direction);
-	Rover(lon + xoff as i32, lat + yoff as i32, *direction)
+    impl Rover {
+	pub fn forward(&self) -> Rover {
+	    let Rover(lon, lat, direction) = self;
+	    let (xoff, yoff) = velocity(&direction);
+	    Rover(lon + xoff as i32, lat + yoff as i32, *direction)
+	}
     }
 
     pub fn backward(slf : &Rover) -> Rover {
@@ -65,7 +67,7 @@ mod driver {
 
     fn perform_command(command: &str, rover: &rover::Rover) -> rover::Rover {
 	match command {
-	    "f" => rover::forward(&rover),
+	    "f" => rover.forward(),
 	    "b" => rover::backward(&rover),
 	    "l" => rover::rotate(&rover, rover::Rotation::Left),
 	    "r" => rover::rotate(&rover, rover::Rotation::Right),
@@ -91,39 +93,39 @@ mod tests {
     #[test]
     fn move_north() {
 	let r = Rover(1 as i32, 1 as i32, rover::Facing::N);
-	assert_eq!(rover::forward(&r),
+	assert_eq!(r.forward(),
 		    Rover(1 as i32, 0 as i32, rover::Facing::N));
 
 	let r =  Rover(1 as i32, 3 as i32, rover::Facing::N);
-	assert_eq!(rover::forward(&r),
+	assert_eq!(r.forward(),
 		   Rover(1 as i32, 2 as i32, rover::Facing::N));
     }
 
     #[test]
     fn move_south() {
 	let r = Rover(1 as i32, 1 as i32, rover::Facing::S);
-	assert_eq!(rover::forward(&r),
+	assert_eq!(r.forward(),
 		   Rover(1 as i32, 2 as i32, rover::Facing::S));
     }
 
     #[test]
     fn move_west() {
 	let r = Rover(1 as i32, 1 as i32, rover::Facing::W);
-	assert_eq!(rover::forward(&r),
+	assert_eq!(r.forward(),
 		   Rover(0 as i32, 1 as i32, rover::Facing::W));
     }
 
     #[test]
     fn move_east() {
 	let r = Rover(1 as i32, 1 as i32, rover::Facing::E);
-	assert_eq!(rover::forward(&r),
+	assert_eq!(r.forward(),
 		   Rover(2 as i32, 1 as i32, rover::Facing::E));
     }
 
     #[test]
     fn move_backward() {
 	let r = Rover(1 as i32, 1 as i32, rover::Facing::E);
-	let r2 = rover::forward(&r);
+	let r2 = r.forward();
 	assert_eq!(rover::backward(&r2), r);
     }