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Xingyu Wang
parent
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commit
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@ -1,193 +0,0 @@
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[#]: collector: (lujun9972)
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[#]: translator: (wxy)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Learn Rust by writing a simple game)
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[#]: via: (https://opensource.com/article/20/12/learn-rust)
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[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
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Learn Rust by writing a simple game
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======
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Start programming with a simple game you can try in multiple languages.
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![Ferris the crab under the sea, unofficial logo for Rust programming language][1]
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When you want to learn a new programming language, it's good to focus on the things programming languages have in common:
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* Variables
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* Expressions
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* Statements
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These concepts are the basis of most programming languages. Once you understand them, you can start figuring the rest out.
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Because programming languages usually share similarities, once you know one language, you can learn the basics of another by understanding its differences.
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A good way to learn new languages is using a standard program that you can use to practice. This allows you to focus on the language, not the program's logic. I'm doing that in this article series using a "guess the number" program, in which the computer picks a number between one and 100 and asks you to guess it. The program loops until you guess the number correctly.
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This program exercises several concepts in programming languages:
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* Variables
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* Input
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* Output
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* Conditional evaluation
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* Loops
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It's a great practical experiment to learn a new programming language.
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### Install Rust
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You can [install a Rust toolchain using Rustup][2], or you can [try Rust online][3] without installing it locally.
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If you install it locally, you should update it periodically with `rustup update` to keep your toolchain fresh, and with `cargo update` to keep your libraries on their latest versions.
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### Guess the number in Rust
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[Rust][4] is a language that empowers anyone to build reliable and efficient software. You can explore Rust by writing a version of the "guess the number" game.
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The first step is to write a `Cargo.toml` file. You can generate a skeleton `Cargo.toml` using the `cargo new` command. This is almost always the best way to start a Rust project.
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```
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$ cargo new guess
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$ cd guess
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$ ls -1
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Cargo.toml
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src/
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```
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The `Cargo.toml` file names your package, gives it some metadata, and, most importantly, specifies that it depends on the `rand` [crate][5].
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```
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[package]
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name = "guess"
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version = "2020.11.0"
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authors = ["Moshe Zadka <[moshez@opensource.com][6]>"]
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edition = "2018"
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# See more keys and their definitions at <https://doc.rust-lang.org/cargo/reference/manifest.html>
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[dependencies]
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rand = "*"
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```
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Many things in Rust are not supplied by the language or the standard library. Instead, you get them from one of many external crates that are available to do many things.
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The program logic goes in `src/main.rs`:
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```
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use rand::Rng;
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use std::io::BufRead;
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fn main() {
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let mut rng = rand::thread_rng();
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let random = rng.gen_range(1..101);
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println!("Guess a number between 1 and 100");
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for line in std::io::stdin().lock().lines() {
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let parsed = line.ok().as_deref().map(str::parse::<i64>);
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if let Some(Ok(guess)) = parsed {
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match guess {
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_ if guess < random => println!("Too low"),
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_ if guess > random => println!("Too high"),
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_ => {
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println!("That's right");
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break;
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}
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}
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}
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}
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}
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```
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The first two lines of the code declare what you are going to do. In this case, `rand::Rng` generates a guess and the [trait][7] `std::io::BufRead` enables reading from standard input.
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The entry point to the Rust code is in the `main()` function, so the next step is to define `main()`.
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To assign a value to a variable put `let`, then the variable's name, followed by the `=` sign. This creates an [immutable][8] variable.
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Most of your variables will be immutable, but the `rng` object must be mutable. For example, the statement `let random = 0` assigns a zero value to the `random` variable.
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The first line of the function creates a thread-safe `Rng` object and assigns it to the variable `rng`. Rust is built on thread and memory safety, so you must think about those things as soon as you start writing code.
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The next line of the program reads the result of the function `gen_range()` and assigns it to the variable called `random`. The function takes a minimum (inclusive) and an upper bound (not inclusive). To make the upper bound inclusive, you can mark the greater number with an equal sign (for example, `1..=100`), or you can just set the upper bound to 1 above your intended maximum, as I've done in my code. In this case, the range is `1` to `100`, making the game just challenging enough.
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The central loop iterates over the lines in `std::io::stdin()`. Since there are all sorts of corner cases that might result in a line not being read, Rust requires you to wrap a line with a `Result`. It might also be impossible for a line to parse an integer.
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This code uses conditional pattern-matching to ignore all lines that would have caused errors:
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```
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let parsed = line.ok().as_deref().map(str::parse::<i64>);
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if let Some(Ok(guess)) = parsed {
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// ...
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}
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```
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The first line creates a `Result<Option<i64>, ...>` object because it might fail at the reading or parsing steps. Since the next line only matches on `Some(Ok(guess))`, whenever a line results in a value that does not match, it skips the `if` statement. This is a powerful way to ignore errors.
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Rust supports conditional expressions and flow control, like loops. In the "guess the number" game, Rust continues looping as long as the value in the guess is not equal to `random`.
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The body of the `if` statement contains a three-way branch using Rust's `match` statement. While `match` is most often used for pattern matching, it can also check arbitrary conditions. In this case, print an appropriate message and `break` the loop if the guess is correct.
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### Sample output
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Now that you've written your Rust program, you can run it to play the "guess the number" game. Every time you run the program, Rust will pick a different random number, so keep guessing until you find the correct number:
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```
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$ cargo run
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Compiling guess v2020.11.0 (/Users/mzadka/src/guess)
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Finished dev [unoptimized + debuginfo] target(s) in 0.70s
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Running `target/debug/guess`
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Guess a number between 1 and 100
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50
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Too high
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25
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Too high
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12
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Too low
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18
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Too high
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15
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Too high
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13
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Too low
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14
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That's right
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```
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It is typical to test the program by running it with `cargo run`. Eventually, you'll probably use `cargo build` to [build an executable and run it][9] as two separate steps.
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### Learn Rust
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This "guess the number" game is a great introductory program for learning a new programming language because it exercises several common programming concepts in a pretty straightforward way. By implementing this simple game in different programming languages, you can demonstrate some core concepts of the languages and compare their details.
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Do you have a favorite programming language? How would you write the "guess the number" game in it? Follow this article series to see examples of other programming languages that might interest you!
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/20/12/learn-rust
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作者：[Moshe Zadka][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/moshez
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/rust_programming_crab_sea.png?itok=2eWLz8A5 (Ferris the crab under the sea, unofficial logo for Rust programming language)
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[2]: https://www.rust-lang.org/learn/get-started
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[3]: https://play.rust-lang.org/
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[4]: https://www.rust-lang.org/
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[5]: https://doc.rust-lang.org/book/ch07-01-packages-and-crates.html
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[6]: mailto:moshez@opensource.com
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[7]: https://doc.rust-lang.org/rust-by-example/trait.html
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[8]: https://en.wikipedia.org/wiki/Immutable_object
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[9]: https://opensource.com/article/20/3/rust-cargo
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186
translated/tech/20201222 Learn Rust by writing a simple game.md
Normal file
186
translated/tech/20201222 Learn Rust by writing a simple game.md
Normal file
@ -0,0 +1,186 @@
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[#]: collector: (lujun9972)
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[#]: translator: (wxy)
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[#]: reviewer: (wxy)
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Learn Rust by writing a simple game)
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[#]: via: (https://opensource.com/article/20/12/learn-rust)
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[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
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通过编写一个简单的游戏来学习 Rust
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======
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> 你可以尝试以多种语言编程一个简单的游戏来开始编程之路。
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![海底的螃蟹 Ferris，Rust 编程语言的非官方标志][1]
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当你想学习一门新的编程语言时，不妨关注一下编程语言的共同点。
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* 变量
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* 表达式
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* 语句
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这些概念是大多数编程语言的基础。一旦你理解了它们，你就可以开始弄清楚其余的东西。
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因为编程语言通常具有相似性，一旦你懂了一种语言，你就可以通过理解其差异来学习另一种语言的基础知识。
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学习新语言的一个好方法是使用一个你可以用来练习的标准程序。这可以让你专注于语言，而不是程序的逻辑。我在这一系列文章中使用了一个“猜数字”的程序，在这个程序中，电脑会在 1 到 100 之间选一个数字让你猜。程序一直循环，直到你猜对数字为止。
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这个程序锻炼了编程语言的几个概念:
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* 变量
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* 输入
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* 输出
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* 条件评估
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* 循环
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这是学习一门新编程语言的很好的实践实验。
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### 安装 Rust
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你可以[使用 Rustup 安装一个 Rust 工具链][2]，或者你可以[在线尝试 Rust][3] 而不在本地安装它。
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如果你在本地安装，你应该定期用 `rustup update` 来更新它，以保持你的工具链的新鲜，并使用 `cargo update` 来保持你的库的最新版本。
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### Rust 语言版本的猜数字
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[Rust][4] 是一门赋予任何人构建可靠和高效的软件能力的语言。你可以通过编写一个 Rust 版本的“猜数字”游戏来探索 Rust。
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第一步是编写一个 `Cargo.toml` 文件。你可以使用 `cargo new` 命令生成一个骨架 `Cargo.toml`。这几乎是开始一个 Rust 项目的最佳方式。
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```
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$ cargo new guess
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$ cd guess
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$ ls -1
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Cargo.toml
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src/
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```
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`Cargo.toml` 文件为你的包命名，并给它一些元数据，最重要的是，指明了它依赖于 `rand` [crate][5]。
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```
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[package]
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name = "guess"
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version = "2020.11.0"
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authors = ["Moshe Zadka <moshez@opensource.com>"]
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edition = "2018"
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# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
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[dependencies]
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rand = "*"
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```
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Rust 中的许多东西不是由语言或标准库提供的。取而代之的是，你可以从某个外部 crate 得到它们，这些 crate 可以做许多事情。
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程序逻辑在 `src/main.rs` 中：
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```
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use rand::Rng;
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use std::io::BufRead;
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fn main() {
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let mut rng = rand::thread_rng();
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let random = rng.gen_range(1..101);
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println!("Guess a number between 1 and 100");
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for line in std::io::stdin().lock().lines() {
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let parsed = line.ok().as_deref().map(str::parse::<i64>);
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if let Some(Ok(guess)) = parsed {
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match guess {
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_ if guess < random => println!("Too low"),
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_ if guess > random => println!("Too high"),
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_ => {
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println!("That's right");
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break;
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}
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}
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}
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}
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}
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```
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代码的前两行声明你要做什么。在本例中，`rand::Rng` 生成一个猜测值，而 [trait][7] `std::io::BufRead` 使得可以从标准输入中读取。
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Rust 代码的入口在 `main()` 函数中，所以下一步就是定义 `main()`。
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要给一个变量赋值，先放 `let`，再放变量的名字，后面放 `=` 号。这样就创建了一个[不可变][8]变量。
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Rust 中大多数变量都是不可变的，但是 `rng` 对象必须是可变的（`mut`）。例如，语句 `let random = 0` 给`random` 变量分配一个零值。
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函数的第一行创建了一个线程安全的 `Rng` 对象，并将其分配给变量 `rng`。Rust 是建立在线程和内存安全的基础上的，所以你必须在开始写代码时就考虑到这些事情。
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程序的下一行读取函数 `gen_range()` 的结果，并将其分配给名为 `random` 的变量。该函数取一个最小值（包含）和一个上界（不包含）。为了也包含上界，你可以用一个等号来标记较大的数字（例如，`1...=100`），或者你也可以像我在代码中做的那样，将上界设置为比你的预期最大值大 1。在这种情况下，该范围是 `1` 到 `100`，使得游戏刚好有足够的挑战性。
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中央循环在 `std::io::stdin()` 中迭代行。由于有各种可能导致行不能读取的例外情况，Rust 要求你用一个 `Result` 来包裹一行。有时候可能无法将一行解析为一个整数。
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这段代码使用条件模式匹配来忽略所有会导致错误的行：
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```
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let parsed = line.ok().as_deref().map(str::parse::<i64>);
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if let Some(Ok(guess)) = parsed {
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// ...
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}
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```
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第一行创建了一个 `Result<Option<i64>, ...>` 对象，因为它可能在读取或解析步骤中失败。由于下一行只在 `Some(Ok(guess))` 上匹配，每当一行的结果是一个不匹配的值时，它就会跳过 `if` 语句。这是一种强大的忽略错误的方法。
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Rust 支持条件表达式和流程控制，比如循环。在“猜数字”游戏中，只要猜中的值不等于 `random`，Rust 就会继续循环。
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`if` 语句的主体包含一个 Rust 的 `match` 语句的三向分支。虽然 `match` 最常用于模式匹配，但它也可以检查任意条件。在这种情况下是打印一个适当的信息，如果猜测是正确的，则中断（`break`）循环。
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### 示例输出
|
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|
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现在你已经写好了你的 Rust 程序，你可以运行它来玩“猜数字”游戏。每次运行程序时，Rust 都会选择一个不同的随机数，所以继续猜，直到找到正确的数字。
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|
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```
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$ cargo run
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Compiling guess v2020.11.0 (/Users/mzadka/src/guess)
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Finished dev [unoptimized + debuginfo] target(s) in 0.70s
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Running `target/debug/guess`
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Guess a number between 1 and 100
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50
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Too high
|
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25
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Too high
|
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12
|
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Too low
|
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18
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Too high
|
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15
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Too high
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13
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Too low
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14
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That's right
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```
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典型的做法是用 `cargo run` 来测试程序。最终，你可能会使用 `cargo build` 分成两个独立的步骤[构建一个可执行文件并运行它][9]。
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|
||||
### 学习 Rust
|
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|
||||
这个“猜数字”游戏是学习一门新的编程语言的一个很好的入门程序，因为它以一种相当直接的方式锻炼了几个常见的编程概念。通过在不同的编程语言中实现这个简单的游戏，你可以展示语言的一些核心概念，并比较它们的细节。
|
||||
|
||||
你有喜欢的编程语言吗？你会如何用它来写“猜数字”游戏呢？请关注本系列文章，看看你可能感兴趣的其他编程语言的例子吧！
|
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|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/20/12/learn-rust
|
||||
|
||||
作者：[Moshe Zadka][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[wxy](https://github.com/wxy)
|
||||
校对：[wxy](https://github.com/wxy)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://opensource.com/users/moshez
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/rust_programming_crab_sea.png?itok=2eWLz8A5 (Ferris the crab under the sea, unofficial logo for Rust programming language)
|
||||
[2]: https://www.rust-lang.org/learn/get-started
|
||||
[3]: https://play.rust-lang.org/
|
||||
[4]: https://www.rust-lang.org/
|
||||
[5]: https://doc.rust-lang.org/book/ch07-01-packages-and-crates.html
|
||||
[6]: mailto:moshez@opensource.com
|
||||
[7]: https://doc.rust-lang.org/rust-by-example/trait.html
|
||||
[8]: https://en.wikipedia.org/wiki/Immutable_object
|
||||
[9]: https://opensource.com/article/20/3/rust-cargo
|
||||
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Reference in New Issue
Block a user