Rust 函数

概述

函数是 Rust 代码的基本构建块。本章将学习函数的定义、参数、返回值、闭包等概念。

🔧 函数基础

函数定义和调用

fn main() {
    println!("Hello, world!");
    
    another_function();
    function_with_parameter(5);
    print_labeled_measurement(5, 'h');
    
    let x = five();
    println!("The value of x is: {}", x);
    
    let x = plus_one(5);
    println!("The value of x is: {}", x);
}

fn another_function() {
    println!("Another function.");
}

fn function_with_parameter(x: i32) {
    println!("The value of x is: {}", x);
}

fn print_labeled_measurement(value: i32, unit_label: char) {
    println!("The measurement is: {}{}", value, unit_label);
}

fn five() -> i32 {
    5
}

fn plus_one(x: i32) -> i32 {
    x + 1
}

🔄 高阶函数

函数作为参数

fn add_one(x: i32) -> i32 {
    x + 1
}

fn do_twice(f: fn(i32) -> i32, arg: i32) -> i32 {
    f(arg) + f(arg)
}

fn main() {
    let answer = do_twice(add_one, 5);
    println!("The answer is: {}", answer);
}

📝 本章小结

函数是 Rust 的核心概念，掌握函数的使用对编写 Rust 程序至关重要。

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继续学习：下一章 - Rust 条件语句