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[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Learn Lua by writing a "guess the number" game)
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[#]: via: (https://opensource.com/article/20/12/lua-guess-number-game)
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[#]: author: (Seth Kenlon https://opensource.com/users/seth)
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Learn Lua by writing a "guess the number" game
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======
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Get to know Lua, a dynamically typed, lightweight, efficient, and
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embeddable scripting language, by programming a simple game.
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![Puzzle pieces coming together to form a computer screen][1]
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If you're a fan of scripting languages like Bash, Python, or Ruby, you might find Lua interesting. Lua is a dynamically typed, lightweight, efficient, and embeddable scripting language with an API to interface with C. It runs by interpreting bytecode with a register-based virtual machine, and it can be used for everything from procedural programming to functional programming to data-driven programming. It can even be used for object-oriented programming through the clever use of arrays, or _tables_, used to mimic classes.
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A great way to get a feel for a language is by writing a simple application you're already familiar with. Recently, some Opensource.com correspondents have demonstrated how to use their favorite languages to create a number-guessing game. [Lua][2] is one of my favorites, so here's my Lua version of the guessing game.
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### Install Lua
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If you're on Linux, you can install Lua from your distribution's software repository. On macOS, you can install Lua from [MacPorts][3] or [Homebrew][4]. On Windows, you can install Lua from [Chocolatey][5].
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Once you have Lua installed, open your favorite text editor and get ready to code.
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### Lua code
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First, you must set up a pseudo-random number generator, so your player has something unpredictable to try to guess. This is a two-step process: first, you start a random seed based on the current time, and then you select a number within the range of 1 to 100:
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```
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math.randomseed(os.[time][6]())
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number = math.random(1,100)
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```
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Next, create what Lua calls a _table_ to represent your player. A table is like an [array in Bash][7] or an ArrayList in Java. You can create a table and then assign child variables associated with that table. In this code, `player` is the table, and `player.guess` is an entry in that table:
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```
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player = {}
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player.guess = 0
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```
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For the purpose of debugging, print the secret number. This isn't good for the game, but it's great for testing. Comments in Lua are preceded by double dashes:
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```
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`print(number) --debug`
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```
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Next, set up a `while` loop that runs forever upon the condition that the value assigned to `player.guess` is not equal to the random `number` established at the start of the code. Currently, `player.guess` is set to 0, so it is not equal to `number`. Lua's math operator for inequality is `~=`, which is admittedly unique, but you get used to it after a while.
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The first thing that happens during this infinite loop is that the game prints a prompt so that the player understands the game.
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Next, Lua pauses and waits for the player to enter a guess. Lua reads from files and standard in (stdin) using the `io.read` function. You can assign the results of `io.read` to a variable that is dynamically created in the `player` table. The problem with the player's input is that it is read as a string, even if it's a number. You can convert this input to an integer type using the `tonumber()` function, assigning the result back to the `player.guess` variable that initially contained 0:
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```
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while ( player.guess ~= number ) do
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print("Guess a number between 1 and 100")
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player.answer = io.read()
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player.guess = tonumber(player.answer)
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```
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Now that `player.guess` contains a new value, it's compared to the random number in an `if` statement. Lua uses the keywords `if`, `elseif`, and `else` and terminates the statement with the keyword `end:`
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```
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if ( player.guess > number ) then
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print("Too high")
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elseif ( player.guess < number) then
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print("Too low")
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else
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print("That's right!")
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os.[exit][8]()
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end
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end
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```
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At the end, the function `os.exit()` closes the application upon success and the keyword `end` is used twice: once to end the `if` statement and again to end the `while` loop.
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### Run the application
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Run the game in a terminal:
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```
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$ lua ./guess.lua
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96
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Guess a number between 1 and 100
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1
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Too low
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Guess a number between 1 and 100
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99
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Too high
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Guess a number between 1 and 100
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96
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That's right!
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```
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That's it!
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### Intuitive and consistent
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As you may be able to tell from this code, Lua is sublimely consistent and fairly intuitive. Its table mechanism is a refreshing way of associating data, and its syntax is minimalistic and efficient. There are few wasted lines in Lua code; in fact, at least one pair of lines in this example could be optimized further, but I wanted to demonstrate data conversion as its own step (maybe you can find the two lines I'm referring to and restructure them).
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Lua is a pleasure to use, and its [documentation is a pleasure to read][9], mostly because there's just not that much to it. You'll learn the core language in no time, and then you'll be free to explore [LuaRocks][10] to discover all the great libraries others have contributed to make your time with Lua even easier. "Lua" means "moon" in Portuguese, so give it a try tonight.
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/20/12/lua-guess-number-game
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作者：[Seth Kenlon][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/seth
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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/puzzle_computer_solve_fix_tool.png?itok=U0pH1uwj (Puzzle pieces coming together to form a computer screen)
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[2]: https://www.lua.org/
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[3]: https://opensource.com/article/20/11/macports
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[4]: https://opensource.com/article/20/6/homebrew-mac
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[5]: https://opensource.com/article/20/3/chocolatey
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[6]: http://www.opengroup.org/onlinepubs/009695399/functions/time.html
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[7]: https://opensource.com/article/20/6/associative-arrays-bash
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[8]: http://www.opengroup.org/onlinepubs/009695399/functions/exit.html
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[9]: https://www.lua.org/docs.html
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[10]: https://opensource.com/article/19/11/getting-started-luarocks
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@ -0,0 +1,129 @@
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[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Learn Lua by writing a "guess the number" game)
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[#]: via: (https://opensource.com/article/20/12/lua-guess-number-game)
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[#]: author: (Seth Kenlon https://opensource.com/users/seth)
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通过编写“猜数字”游戏学习 Lua
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======
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通过编写一个简单的游戏来认识 Lua，它是一种动态类型的、轻量级的、高效的、可嵌入的脚本语言。
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![Puzzle pieces coming together to form a computer screen][1]
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如果你是 Bash、Python 或 Ruby 等脚本语言的爱好者，你可能会发现 Lua 很有趣。Lua 是一种动态类型的、轻量级的、高效的、可嵌入的脚本语言，它有与 C 语言的 API 接口。它通过解释字节码与基于寄存器的虚拟机来运行，它可以用于从过程式编程到函数式编程再到数据驱动编程。它甚至可以通过巧妙地使用数组或_表_来模拟类，以用于面向对象的编程。
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感受一门语言的好方法是通过编写一个你已经熟悉的简单应用。最近，一些 Opensource.com 的通讯员已经演示了如何使用他们最喜欢的语言来创建一个数字猜测游戏。[Lua][2] 是我最喜欢的语言之一，所以这是我的 Lua 版猜数游戏。
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### 安装 Lua
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如果你是在 Linux 上，你可以从你的发行版仓库中安装 Lua。在 macOS 上，你可以从 [MacPorts][3] 或 [Homebrew][4] 安装 Lua。在 Windows 上，你可以从 [Chocolatey][5] 安装 Lua。
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安装 Lua 后，打开你最喜欢的文本编辑器，可以准备编写了。
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### Lua 代码
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首先，你必须设置一个伪随机数生成器，这样你的玩家就有一些不可预知的东西来尝试猜测。这是一个两个步骤的过程：首先，你根据当前的时间生成一个随机种子，然后在 1 到 100 的范围内选择一个数字：
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```
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math.randomseed(os.[time][6]())
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number = math.random(1,100)
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```
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接下来，创建一个 Lua 所谓的_表_来表示你的玩家。表就像一个 [Bash 中的数组][7]或 Java 中的 ArrayList。你可以创建一个表，然后分配与该表相关的子变量。在这段代码中，`player` 是表，而 `player.guess` 是表中的一个条目：
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```
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player = {}
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player.guess = 0
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```
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为了调试打印秘密数字。这对游戏不好，但对测试很有帮助。Lua 中的注释前面有双破折号：
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```
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`print(number) --debug`
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```
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接下来，设置一个 `while` 循环，当分配给 `player.guess` 的值不等于代码开始时建立的随机 `number` 时，循环将永远运行。目前，`player.guess` 被设置为 0，所以它不等于 `number`。Lua 的不等式数学运算符是 `~=`，诚然这很独特，但过一段时间你就会习惯。
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在这个无限循环的过程中，首先游戏会打印一个提示，让玩家明白游戏的内容。
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接下来，Lua 会暂停，等待玩家输入猜测。Lua 使用 `io.read` 函数从文件和标准输入 （stdin） 中读取数据。你可以将 `io.read`的结果分配到一个变量中，这个变量是在 `player` 表中动态创建的。玩家输入的问题是，即使它是一个数字，它也是作为一个字符串读取的。你可以使用 `tonumber()` 函数将这个输入转换为整数类型，将结果赋值回初始为 0 的 `player.guess` 变量：
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```
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while ( player.guess ~= number ) do
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print("Guess a number between 1 and 100")
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player.answer = io.read()
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player.guess = tonumber(player.answer)
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```
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现在 `player.guess` 包含了一个新的值，它将与 `if` 语句中的随机数进行比较。Lua 使用关键字 `if`、`elseif` 和 `else`，并用关键字 `end` 来结束语句：
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```
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if ( player.guess > number ) then
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print("Too high")
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elseif ( player.guess < number) then
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print("Too low")
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else
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print("That's right!")
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os.[exit][8]()
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end
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end
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```
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最后，函数 `os.exit()` 在成功后关闭应用，关键字 `end` 使用了两次：一次是结束 `if` 语句，另一次是结束 `while` 循环。
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### 运行应用
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在终端上运行游戏：
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```
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$ lua ./guess.lua
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96
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Guess a number between 1 and 100
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1
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Too low
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Guess a number between 1 and 100
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99
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Too high
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Guess a number between 1 and 100
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96
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That's right!
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```
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就是这样！
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### 直观且一致
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从这段代码中可以看出，Lua 是非常一致且相当直观的。它的表机制是一种令人耳目一新的数据关联方式，它的语法也是简约而高效的。Lua 代码中几乎没有浪费的行数，事实上，这个例子中至少有两行可以进一步优化，但我想把数据转换作为它的步骤来演示（也许你可以找到我所指的两行，并对它们进行重组）。
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Lua 使用起来很愉快，它的[文档阅读起来很愉快][9]，主要是因为它的内容实在是不多。你会在短时间内学会核心语言，然后你就可以自由地探索 [LuaRocks][10]，发现别人贡献的所有很棒的库。
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/20/12/lua-guess-number-game
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作者：[Seth Kenlon][a]
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选题：[lujun9972][b]
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译者：[geekpi](https://github.com/geekpi)
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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/seth
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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/puzzle_computer_solve_fix_tool.png?itok=U0pH1uwj (Puzzle pieces coming together to form a computer screen)
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[2]: https://www.lua.org/
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[3]: https://opensource.com/article/20/11/macports
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[4]: https://opensource.com/article/20/6/homebrew-mac
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[5]: https://opensource.com/article/20/3/chocolatey
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[6]: http://www.opengroup.org/onlinepubs/009695399/functions/time.html
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[7]: https://opensource.com/article/20/6/associative-arrays-bash
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[8]: http://www.opengroup.org/onlinepubs/009695399/functions/exit.html
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[9]: https://www.lua.org/docs.html
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[10]: https://opensource.com/article/19/11/getting-started-luarocks
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