deduplicate code in rotate method

src/main.rs

@@ -8,7 +8,8 @@ mod rover {
     #[derive(Debug, PartialEq, Copy, Clone)]
     pub enum Rotation { Left, Right }
 
-    pub type Rover = (i32, i32, Facing);
+    #[derive(Debug, PartialEq, Copy, Clone)]
+    pub struct Rover(pub i32, pub i32, pub Facing);
 
     fn velocity(direction : &Facing) -> (i32, i32) {
 	match direction {
@@ -19,16 +20,6 @@ mod rover {
 	}
     }
 
-    pub fn forward((lon, lat, direction) : &Rover) -> Rover {
-	let (xoff, yoff) = velocity(&direction);
-	(lon + xoff as i32, lat + yoff as i32, *direction)
-    }
-
-    pub fn backward((lon, lat, direction) : &Rover) -> Rover {
-	let (xoff, yoff) = velocity(&direction);
-	(lon - xoff as i32, lat - yoff as i32, *direction)
-    }
-
     fn next_direction(direction : Facing) -> Facing {
 	match direction {
 	    Facing::N => Facing::W,
@@ -38,18 +29,34 @@ mod rover {
 	}
     }
 
-    pub fn rotate((lon, lat, direction) : &Rover, rotation: Rotation) -> Rover {
-	match rotation {
-	    Rotation::Left => {
-		let new_d = next_direction(*direction);
-		(*lon, *lat, new_d)
-	    },
-	    Rotation::Right => {
-		let new_d = next_direction(*direction);
-		let new_d = next_direction(new_d);
-		let new_d = next_direction(new_d);
-		(*lon, *lat, new_d)
-	    }
+    impl Rover {
+	pub fn forward(&self) -> Rover {
+	    let Rover(lon, lat, direction) = self;
+	    let (xoff, yoff) = velocity(&direction);
+	    Rover(lon + xoff, lat + yoff, *direction)
+	}
+
+	pub fn backward(&self) -> Rover {
+	    let Rover(lon, lat, direction) = self;
+	    let (xoff, yoff) = velocity(&direction);
+	    Rover(lon - xoff, lat - yoff, *direction)
+	}
+
+	pub fn rotate(&self, rotation: Rotation) -> Rover {
+	    let Rover(lon, lat, direction) = self;
+	    let new_direction = match rotation {
+		Rotation::Left => {
+		    next_direction(*direction)
+		},
+		Rotation::Right => {
+		    next_direction(
+			next_direction(
+			    next_direction(*direction)
+			)
+		    )
+		}
+	    };
+	    Rover(*lon, *lat, new_direction)
 	}
     }
 }
@@ -60,10 +67,10 @@ mod driver {
 
     fn perform_command(command: &str, rover: &rover::Rover) -> rover::Rover {
 	match command {
-	    "f" => rover::forward(&rover),
-	    "b" => rover::backward(&rover),
-	    "l" => rover::rotate(&rover, rover::Rotation::Left),
-	    "r" => rover::rotate(&rover, rover::Rotation::Right),
+	    "f" => rover.forward(),
+	    "b" => rover.backward(),
+	    "l" => rover.rotate(rover::Rotation::Left),
+	    "r" => rover.rotate(rover::Rotation::Right),
 	    _ => rover.clone()
 	}
     }
@@ -80,67 +87,67 @@ mod driver {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
+    use super::driver;
+    use super::rover::{Rover, Facing,Rotation};
 
     #[test]
     fn move_north() {
-	let r = (1 as i32, 1 as i32, rover::Facing::N);
-	assert_eq!(rover::forward(&r),
-		   (1 as i32, 0 as i32, rover::Facing::N));
+	let r = Rover(1, 1, Facing::N);
+	assert_eq!(r.forward(),
+		    Rover(1, 0, Facing::N));
 
-	let r = (1 as i32, 3 as i32, rover::Facing::N);
-	assert_eq!(rover::forward(&r),
-		   (1 as i32, 2 as i32, rover::Facing::N));
+	let r =  Rover(1, 3, Facing::N);
+	assert_eq!(r.forward(),
+		   Rover(1, 2, Facing::N));
     }
 
     #[test]
     fn move_south() {
-	let r = (1 as i32, 1 as i32, rover::Facing::S);
-	assert_eq!(rover::forward(&r),
-		   (1 as i32, 2 as i32, rover::Facing::S));
+	let r = Rover(1, 1, Facing::S);
+	assert_eq!(r.forward(),
+		   Rover(1, 2, Facing::S));
     }
 
     #[test]
     fn move_west() {
-	let r = (1 as i32, 1 as i32, rover::Facing::W);
-	assert_eq!(rover::forward(&r),
-		   (0 as i32, 1 as i32, rover::Facing::W));
+	let r = Rover(1, 1, Facing::W);
+	assert_eq!(r.forward(),
+		   Rover(0, 1, Facing::W));
     }
 
     #[test]
     fn move_east() {
-	let r = (1 as i32, 1 as i32, rover::Facing::E);
-	assert_eq!(rover::forward(&r),
-		   (2 as i32, 1 as i32, rover::Facing::E));
+	let r = Rover(1, 1, Facing::E);
+	assert_eq!(r.forward(),
+		   Rover(2, 1, Facing::E));
     }
 
     #[test]
     fn move_backward() {
-	let r = (1 as i32, 1 as i32, rover::Facing::E);
-	let r2 = rover::forward(&r);
-	assert_eq!(rover::backward(&r2), r);
+	let r = Rover(1, 1, Facing::E);
+	let r2 = r.forward();
+	assert_eq!(r2.backward(), r);
     }
 
     #[test]
     fn spin_left() {
-	let r = (1 as i32, 1 as i32, rover::Facing::E);
-	match rover::rotate(&r, rover::Rotation::Left) {
-	    (_, _, facing) => assert_eq!(facing, rover::Facing::N)
+	let r = Rover(1, 1, Facing::E);
+	match r.rotate(Rotation::Left) {
+	    Rover(_, _, facing) => assert_eq!(facing, Facing::N)
 	}
     }
     #[test]
     fn spin_right() {
-	let r = (1 as i32, 1 as i32, rover::Facing::S);
-	match rover::rotate(&r, rover::Rotation::Right) {
-	    (_, _, facing) => assert_eq!(facing, rover::Facing::W)
+	let r = Rover(1, 1, Facing::S);
+	match r.rotate(Rotation::Right) {
+	    Rover(_, _, facing) => assert_eq!(facing, Facing::W)
 	}
     }
 
     #[test]
     fn drive() {
-	let r = (1 as i32, 1 as i32, rover::Facing::S);
+	let r = Rover(1, 1, Facing::S);
 	assert_eq!(driver::execute(&r, "ffrf"),
-		   (0 as i32, 3 as i32, rover::Facing::W));
+		   Rover(0, 3, Facing::W));
     }
-
 }