rust 初学

概览

基本概念

Rust 定义变量、函数和数据结构

控制流程

例子

下载 url 为 md 文件

在 terminal 输入 cargo run -- https://www.rust-lang.org rust.md

即是把 https://www.rust-lang.org 下载到 rust.md

Cargo.toml

[package]
name = "scrape_url"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
reqwest = { version = "0.11", features = ['blocking'] }
html2md = "0.2"

main.rs

use std::fs;

fn md_params() -> Result<(String, String), Box<dyn std::error::Error>> {
    let url = std::env::args().nth(1).expect("Missing argument");
    let output = std::env::args().nth(2).expect("Missing argument");
    Ok((url, output))
}

fn main() {
    // let url = "https://www.rust-lang.org/";
    // let output = "rust.md";

    let result = md_params();

    match result {
        Ok((url, output)) => {
            println!("Fetching url: {}", url);
            let body = reqwest::blocking::get(url).unwrap().text().unwrap();

            println!("Converting html to markdown...");
            let md = html2md::parse_html(&body);

            println!("Converted markdown has been saved in {}.", output);
            fs::write(output, md.as_bytes()).unwrap();
        }
        Err(err) => {
            println!("Error: {}", err.to_string());
        }
    }
}

费波纳基数列

main.rs

fn next_fiber(a: &mut i32, b: &mut i32) {
    let c = *a + *b;
    *a = *b;
    *b = c;
}

fn fib_loop(n: u8) {
    let mut a = 1;
    let mut b = 1;
    let mut i = 2u8;
    loop {
        // let c = a + b;
        // a = b;
        // b = c;
        next_fiber(&mut a, &mut b);
        i += 1;
        println!("next val is {}", b);
        if i >= n {
            break;
        }
    }
}
fn fib_while(n: u8) {
    let (mut a, mut b, mut i) = (1, 1, 2);
    while i < n {
        // let c = a + b;
        // a = b;
        // b = c;
        next_fiber(&mut a, &mut b);
        i += 1;
        println!("next val is {}", b);
    }
}
fn fib_for(n: u8) {
    let (mut a, mut b) = (1, 1);
    for _i in 2..n {
        // let c = a + b;
        // a = b;
        // b = c;
        next_fiber(&mut a, &mut b);
        println!("next val is {}", b);
    }
}
fn main() {
    let n = 10;
    fib_loop(n);
    fib_while(n);
    fib_for(n);
}