Battleship Tutorial

This tutorial demonstrates transactions and state management through a simplified Battleship game.

Overview

The game creates two board objects, places ships via setState, and resolves attacks by checking coordinates against the stored ship list.

Board behavior

The board behavior handles two message types:

• ["ship", x, y, length] — place a ship by reading the current state, appending the ship, and writing back.
• ["coord", x, y] — check if the coordinate hits any ship.

"ship" => {
    avm_do! {
        let current_state <- trigger(get_state());
        let new_state = { /* append ship to list */ };
        trigger(set_state(new_state));
        ret(Val::Bool(true))
    }
}
"coord" => {
    avm_do! {
        let current_state <- trigger(get_state());
        let hit = /* check if (x,y) intersects any ship */;
        ret(Val::Bool(hit))
    }
}

Game setup

avm_do! {
    // Atomic creation
    let tx <- trigger(begin_tx(None));
    let board1 <- trigger(create_obj("board", None));
    let board2 <- trigger(create_obj("board", None));
    trigger(commit_tx(tx));

    // Place ships
    trigger(call(board1, ship(0, 0, 3)));
    trigger(call(board2, ship(1, 1, 4)));

    // Attack
    let hit  <- trigger(call(board2, coord(1, 1)));  // hit!
    let miss <- trigger(call(board2, coord(9, 9)));  // miss
    ret(Val::list(vec![hit, miss]))
}

Key concepts demonstrated

• Transactional creation: both boards are created atomically.
• State management: get_state / set_state maintain ship lists across calls.
• Message-based dispatch: the board behavior pattern-matches on the input message tag to decide what to do.