// 闭包测试 — lambda 表达式 + 调用
fn apply_op(x: i64, op: i64) -> i64 {
    // 闭包作为参数暂不支持直接调用，返回 x * 2
    return x * 2;
}

fn main() -> void {
    // 测试1: 基本 lambda
    let double = fn(x: i64) -> i64 { return x * 2; };
    let r1 = double(21);
    print_i64(r1);  // 42

    // 测试2: lambda with multiple params
    let add = fn(a: i64, b: i64) -> i64 { return a + b; };
    let r2 = add(30, 12);
    print_i64(r2);  // 42

    // 测试3: nested lambda call
    let r3 = double(add(10, 11));
    print_i64(r3);  // 42

    // 测试4: lambda in sequence
    let triple = fn(x: i64) -> i64 { return x * 3; };
    let r4 = triple(14);
    print_i64(r4);  // 42
}