Achieve the final result of entirely generic!!

src/system/sticker.rs

@@ -0,0 +1,29 @@
+use rand::Rng;
+use crate::system::{GriddedPosition, Position, Storage};
+
+pub trait Sticker<P: Position> {
+    fn should_stick<R: Rng, S: Storage<P>>(&self, rng: &mut R, space: &S, position: &P) -> bool;
+}
+
+pub struct SimpleSticking;
+
+pub struct ProbabilisticSticking {
+    pub stick_probability: f32
+}
+
+impl<P: GriddedPosition> Sticker<P> for SimpleSticking {
+    fn should_stick<R: Rng, S: Storage<P>>(&self, rng: &mut R, space: &S, position: &P) -> bool {
+        (0..P::NEIGHBOURS)
+            .map(|n| position.neighbour(n))
+            .any(|neighbour| space.at(&neighbour))
+    }
+}
+
+impl<P: GriddedPosition> Sticker<P> for ProbabilisticSticking {
+    fn should_stick<R: Rng, S: Storage<P>>(&self, rng: &mut R, space: &S, position: &P) -> bool {
+        (0..P::NEIGHBOURS)
+            .map(|n| position.neighbour(n))
+            .any(|neighbour| space.at(&neighbour) && rng.gen_range(0.0f32..=1.0) < self.stick_probability)
+    }
+}
+