start tutorial

tutorial/03-rust-ownership-borrow/task/Cargo.toml

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+[package]
+name = "step03_rust_ownership_borrow_task"
+version = "0.1.0"
+edition = "2021"

tutorial/03-rust-ownership-borrow/task/src/main.rs

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+#[derive(Debug)]
+struct RobotState {
+    led_on: bool,
+    button_count: u32,
+    last_adc: u16,
+}
+
+fn print_state(state: &RobotState) {
+    println!(
+        "state => led_on={}, button_count={}, last_adc={}",
+        state.led_on, state.button_count, state.last_adc
+    );
+}
+
+fn toggle_led(state: &mut RobotState) {
+    state.led_on = !state.led_on;
+}
+
+fn record_button_press(state: &mut RobotState) {
+    state.button_count += 1;
+}
+
+fn update_adc(state: &mut RobotState, raw: u16) {
+    // TODO: keep this function as the single writer for ADC state.
+    state.last_adc = raw;
+}
+
+fn main() {
+    let mut state = RobotState {
+        led_on: false,
+        button_count: 0,
+        last_adc: 0,
+    };
+
+    print_state(&state);
+
+    toggle_led(&mut state);
+    record_button_press(&mut state);
+    update_adc(&mut state, 2024);
+
+    print_state(&state);
+}