first?

.gitignore

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+/target
+
+.vscode

Cargo.toml

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+[package]
+name = "rulebot"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+reqwest = { version = "0.11.16", features = ["blocking"] }
+exitcode = "1.1.2"
+rand = "0.8.5"

README.md

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+RuleBot
+=======
+
+Bot that runs a random ![cellular automaton](https://en.wikipedia.org/wiki/Elementary_cellular_automaton) on an 8-bit input.

src/main.rs

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+use rand::Rng;
+
+type State = [bool; 8];
+
+fn map_state(rule: u8, state: &State) -> State {
+    let mut new_state: [bool; 8] = [false; 8];
+
+    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;
+    }
+
+    new_state
+}
+
+fn state_to_string(state: State) -> String {
+    state.map(|c| if c { "⬛" } else { "⬜" }).concat()
+}
+
+fn num_to_state(num: u8) -> State {
+    let mut state = [false; 8];
+
+    for i in 0..8 {
+        state[i] = (num >> i & 1) == 1;
+    }
+
+    state
+}
+
+fn main() {
+    let mut rng = rand::thread_rng();
+    let seed: u16 = rng.gen();
+
+    let rule: u8 = (seed & 0xff) as u8;
+    let init_state = num_to_state((seed >> 8 & 0xff) as u8);
+
+    let states: String = (0..8)
+        .scan(init_state, |state, _i| {
+            let old_state = *state;
+            *state = map_state(rule, state);
+            Some(old_state)
+        })
+        .map(state_to_string)
+        .collect::<Vec<String>>()
+        .join("\n");
+
+    println!("Rule: {}\n{}", rule, states);
+
+    let client = reqwest::blocking::Client::new();
+    let res = client
+        .post("https://mastodon.raptorpond.com/api/v1/statuses")
+        .header(
+            "Authorization",
+            format!("Bearer {}", std::env::var("MASTODON_TOKEN").unwrap()),
+        )
+        .form(&[
+            ("status", format!("Rule: {}\n{}", rule, states)),
+            ("visibility", String::from("private")),
+        ])
+        .send();
+
+    match res {
+        Ok(_) => std::process::exit(exitcode::OK),
+        Err(error) => {
+            println!("{:?}", error);
+            std::process::exit(exitcode::IOERR);
+        }
+    }
+}