2021 day5/rust: avoid nightly for line point iterator

2021/day5/day5_rs/src/main.rs

@@ -1,7 +1,5 @@
-#![feature(int_abs_diff)]
 #![warn(clippy::pedantic)]
 use std::{
-    cmp::Ordering,
     convert::Infallible,
     io::{stdin, BufRead},
     str::FromStr,
@@ -40,25 +38,24 @@ impl FromStr for Line {
 }
 
 struct LinePoints {
-    pos: Vector2D<usize>,
-    x_change: Ordering,
-    y_change: Ordering,
+    pos: Vector2D<isize>,
+    step: Vector2D<isize>,
     points_left: usize,
 }
 
 impl LinePoints {
     fn new(line: &Line) -> Self {
-        let x_change = line.end.x.cmp(&line.start.x);
-        let y_change = line.end.y.cmp(&line.start.y);
+        let start = line.start.as_isizes();
+        let end = line.end.as_isizes();
+        let delta = end - start;
+        let step = Vector2D::new(delta.x.signum(), delta.y.signum());
 
-        let delta_x = line.end.x.abs_diff(line.start.x);
-        let delta_y = line.end.y.abs_diff(line.start.y);
+        let len = usize::max(delta.x.unsigned_abs(), delta.y.unsigned_abs());
 
         Self {
-            pos: line.start,
-            x_change,
-            y_change,
-            points_left: usize::max(delta_x, delta_y) + 1,
+            pos: start,
+            step,
+            points_left: len + 1,
         }
     }
 }
@@ -72,18 +69,9 @@ impl Iterator for LinePoints {
         }
 
         let current = self.pos;
-        match self.x_change {
-            Ordering::Less => self.pos.x -= 1,
-            Ordering::Greater => self.pos.x += 1,
-            Ordering::Equal => {}
-        }
-        match self.y_change {
-            Ordering::Less => self.pos.y -= 1,
-            Ordering::Greater => self.pos.y += 1,
-            Ordering::Equal => {}
-        }
+        self.pos += self.step;
         self.points_left -= 1;
-        Some(current)
+        Some(current.as_usizes())
     }
 }