2020: day12: refacto part 1 directions iterator
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@ -35,7 +35,7 @@ enum Direction {
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West,
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}
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#[derive(Debug, Clone, Copy)]
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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enum ActionKind {
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Move(Direction),
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@ -114,45 +114,42 @@ impl Ship {
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self.x.abs() + self.y.abs()
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}
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fn find_direction<I>(iter: I, quarters: usize, current_direction: Direction) -> Direction
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where
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I: Iterator<Item = Direction>,
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I: std::clone::Clone,
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{
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iter
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// this is litteraly a circle, reaching West and turning 90 degrees right means
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// facing North again
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.cycle()
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// find our current ship direction
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.skip_while(|dir| *dir != current_direction)
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// skip as many quarters as needed
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.nth(quarters)
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// we can unwrap safely because we called .cycle() on a non empty iterator
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.unwrap()
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}
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fn process(&mut self, action: Action) {
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match action.kind {
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ActionKind::Move(dir) => self.forward(dir, action.arg),
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ActionKind::Right => {
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ActionKind::Right | ActionKind::Left => {
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debug_assert!(action.arg % 90 == 0, "only right angles are supported");
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let quarters = action.arg / 90;
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let quarters = (action.arg / 90) as usize;
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let new_dir = Self::CLOCKWISE_DIRECTIONS
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.iter()
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// this is litteraly a circle, reaching West and turning 90 degrees right means
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// facing North again
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.cycle()
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// find our current ship direction
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.skip_while(|dir| **dir != self.direction)
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// skip as many quarters as needed
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.nth(quarters as usize)
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// we can unwrap safely because we called .cycle() on a non empty iterator
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.unwrap();
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let directions_iter = Self::CLOCKWISE_DIRECTIONS.iter().copied();
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self.direction = *new_dir;
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}
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let new_dir = if action.kind == ActionKind::Left {
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// go through cardinal directions the other way around, anti-clockwise
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Ship::find_direction(directions_iter.rev(), quarters, self.direction)
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} else {
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Ship::find_direction(directions_iter, quarters, self.direction)
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};
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ActionKind::Left => {
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debug_assert!(action.arg % 90 == 0, "only right angles are supported");
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let quarters = action.arg / 90;
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let new_dir = Self::CLOCKWISE_DIRECTIONS
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.iter()
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// same thing as above, but reverse direction first!
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.rev()
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.cycle()
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.skip_while(|dir| **dir != self.direction)
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.nth(quarters as usize)
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.unwrap();
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self.direction = *new_dir;
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self.direction = new_dir;
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}
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ActionKind::Forward => self.forward(self.direction, action.arg),
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