Lambda 表达式

Lambda 是内联的匿名函数。

语法

(parameters) => expression

简单示例：

let double = (x: int) => x * 2;

多行 lambda 使用花括号：

let greet = (name: string) => {
    say("Hello, ${name}!");
    say("Welcome to the server!");
};

高阶函数

接受其他函数作为参数的函数：

fn apply_to_all(targets: selector, action: (selector) => void) {
    action(targets);
}

apply_to_all(@a, (s: selector) => {
    effect(s, "speed", 10, 2);
});

for_each

对集合中的每个元素应用 lambda：

let teams: string[] = ["red", "blue", "green"];

for_each(teams, (team: string) => {
    team_add(team);
    say("Created team: ${team}");
});

map

转换值：

let scores: int[] = [10, 20, 30];
let doubled: int[] = map(scores, (x: int) => x * 2);
// [20, 40, 60]

filter

筛选匹配的值：

let scores: int[] = [5, 15, 25, 35];
let high: int[] = filter(scores, (x: int) => x > 20);
// [25, 35]

闭包

Lambda 可以捕获外层作用域的变量：

let bonus: int = 10;

let add_bonus = (score: int) => score + bonus;

add_bonus(5);  // 15
add_bonus(20); // 30

更实际的例子：

fn create_reward(base_xp: int) {
    let give_reward = (player: selector) => {
        xp_add(player, base_xp);
        say("Rewarded ${base_xp} XP!");
    };

    give_reward(@a[tag=winner]);
}

实际示例

使用 lambda 构建可配置的事件系统：

let on_game_start: () => void = () => {
    say("Game started!");
    effect(@a, "speed", 30, 1);
};

let on_game_end: () => void = () => {
    say("Game over!");
    clear(@a);
};

fn trigger_event(handler: () => void) {
    handler();
}

@load
fn init() {
    trigger_event(on_game_start);
}

下一步

• NBT 数据 — 使用 Minecraft NBT
• 选择器 — 定位实体