Move the proximity function to a module

src/proximity.rs

@@ -0,0 +1,28 @@
+use std::cmp;
+use crate::{Attribute, Position};
+
+const ONE_ATTRIBUTE: u32 = 1000;
+const MAX_DISTANCE: u32 = 8;
+
+pub fn index_proximity(lhs: u32, rhs: u32) -> u32 {
+    if lhs <= rhs {
+        cmp::min(rhs - lhs, MAX_DISTANCE)
+    } else {
+        cmp::min((lhs - rhs) + 1, MAX_DISTANCE)
+    }
+}
+
+pub fn positions_proximity(lhs: Position, rhs: Position) -> u32 {
+    let (lhs_attr, lhs_index) = extract_position(lhs);
+    let (rhs_attr, rhs_index) = extract_position(rhs);
+    if lhs_attr != rhs_attr { MAX_DISTANCE }
+    else { index_proximity(lhs_index, rhs_index) }
+}
+
+pub fn extract_position(position: Position) -> (Attribute, Position) {
+    (position / ONE_ATTRIBUTE, position % ONE_ATTRIBUTE)
+}
+
+pub fn path_proximity(path: &[Position]) -> u32 {
+    path.windows(2).map(|w| positions_proximity(w[0], w[1])).sum::<u32>()
+}