move to iterator

src/main.rs

@@ -1,11 +1,25 @@
-use std::{fmt::Display, future::Future, ops::Index, time::Duration};
+use std::{
+    fmt::Display,
+    future::Future,
+    ops::{Index, IndexMut},
+    time::Duration,
+};
 
 use rand::Rng;
 use tokio::{signal, time};
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, Default)]
 struct State([bool; 8]);
 
+impl State {
+    fn rule_iterator(&self, rule: u8) -> impl Iterator<Item = State> {
+        StateIterator {
+            rule: rule,
+            state: *self,
+        }
+    }
+}
+
 impl Index<usize> for State {
     type Output = bool;
 
@@ -14,17 +28,35 @@ impl Index<usize> for State {
     }
 }
 
-fn map_state(rule: u8, state: &State) -> State {
-    let mut new_state: [bool; 8] = [false; 8];
+impl IndexMut<usize> for State {
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        &mut self.0[index]
+    }
+}
+
+struct StateIterator {
+    rule: u8,
+    state: State,
+}
+
+impl Iterator for StateIterator {
+    type Item = State;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let old_state = self.state;
+        let mut new_state = State::default();
 
         for i in 0..8 {
-        let pattern = ((i != 0 && state[i - 1]) as u8 * 4)
-            | (state[i] as u8 * 2)
-            | ((i != 7 && state[i + 1]) as u8);
-        new_state[i] = (rule >> pattern & 1) == 1;
+            let pattern = ((i != 0 && self.state[i - 1]) as u8 * 4)
+                | (self.state[i] as u8 * 2)
+                | ((i != 7 && self.state[i + 1]) as u8);
+            new_state[i] = (self.rule >> pattern & 1) == 1;
         }
 
-    State(new_state)
+        self.state = new_state;
+
+        Some(old_state)
+    }
 }
 
 impl Display for State {
@@ -72,14 +104,11 @@ fn send_status(
 
 fn generate(seed: u16) -> String {
     let rule: u8 = (seed & 0xff) as u8;
-    let init_state = ((seed >> 8 & 0xff) as u8).into();
+    let init_state: State = ((seed >> 8 & 0xff) as u8).into();
 
-    (0..8)
-        .scan(init_state, |state, _i| {
-            let old_state = *state;
-            *state = map_state(rule, state);
-            Some(old_state)
-        })
+    init_state
+        .rule_iterator(rule)
+        .take(8)
         .map(|state| state.to_string())
         .collect::<Vec<String>>()
         .join("\n")