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[#]: collector: (lujun9972)
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[#]: translator: ( )
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Program a simple game with Elixir)
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[#]: via: (https://opensource.com/article/20/12/elixir)
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[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
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Program a simple game with Elixir
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======
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Learn Elixir by programming a "guess the number" game and comparing the
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language against ones you know.
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![A die with rainbow color background][1]
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To you learn a new programming language, it's good to focus on the things most 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. Because of these similarities, once you know one programming language, you can start figuring another one out by recognizing its differences.
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Another good tool for learning a new language is starting with a standard program. This allows you to focus on the language, not the program's logic. We're 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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The "guess the number" 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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### Guess the number in Elixir
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The [Elixir][2] programming language is a dynamically typed functional language designed for building stable and maintainable applications. It runs on top of the same virtual machine as [Erlang][3] and shares many of its strengths—but with slightly easier syntax.
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You can explore Elixir by writing a version of the "guess the number" game.
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Here is my implementation:
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```
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defmodule Guess do
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def guess() do
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random = Enum.random(1..100)
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IO.puts "Guess a number between 1 and 100"
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Guess.guess_loop(random)
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end
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def guess_loop(num) do
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data = IO.read(:stdio, :line)
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{guess, _rest} = Integer.parse(data)
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cond do
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guess < num ->
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IO.puts "Too low!"
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guess_loop(num)
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guess > num ->
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IO.puts "Too high!"
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guess_loop(num)
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true ->
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IO.puts "That's right!"
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end
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end
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end
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Guess.guess()
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```
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To assign a value to a variable, list the variable's name followed by the `=` sign. For example, the statement `random = 0` assigns a zero value to the `random` variable.
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The script starts by defining a **module**. In Elixir, only modules can have named functions in them.
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The next line defines the function that will serve as the entry point, `guess()`, which:
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* Calls the `Enum.random()` function to get a random integer
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* Prints the game prompt
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* Calls the function that will serve as the loop
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The rest of the game logic is implemented in the `guess_loop()` function.
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The `guess_loop()` function uses [tail recursion][4] to loop. There are several ways to do looping in Elixir, but using tail recursion is a common one. The last thing `guess_loop()` does is call _itself_.
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The first line in `guess_loop()` reads the input from the user. The next line uses `parse()` to convert the input to an integer.
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The `cond` statement is Elixir's version of a multi-branch statement. Unlike `if/elif` or `if/elsif` in other languages, Elixir does not treat the first nor the last branch in a different way.
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This `cond` statement has a three-way branch: The guess can be smaller, bigger, or equal to the random number. The first two options output the inequality's direction and then tail-call `guess_loop()`, looping back to the beginning. The last option outputs `That's right`, and the function finishes.
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### Sample output
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Now that you've written your Elixir program, you can run it to play the "guess the number" game. Every time you run the program, Elixir will pick a different random number, and you can guess until you find the correct number:
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```
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$ elixir guess.exs
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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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30
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Too high
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20
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Too high
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10
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Too low
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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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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/elixir
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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/dice_tabletop_board_gaming_game.jpg?itok=y93eW7HN (A die with rainbow color background)
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[2]: https://elixir-lang.org/
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[3]: https://www.erlang.org/
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[4]: https://en.wikipedia.org/wiki/Tail_call
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137
translated/tech/20201209 Program a simple game with Elixir.md
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137
translated/tech/20201209 Program a simple game with Elixir.md
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@ -0,0 +1,137 @@
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[#]: collector: (lujun9972)
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[#]: translator: (tt67wq)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Program a simple game with Elixir)
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[#]: via: (https://opensource.com/article/20/12/elixir)
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[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
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使用 Elixir 语言编写一个小游戏
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======
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通过编写"猜数字"游戏来学习 Elixir 编程语言并将它与一个你熟知的语言做对比。
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![A die with rainbow color background][1]
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为了更好的学习一门新的编程语言，最好的方法是去关注主流语言的一些共有特征：
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* 变量
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* 表达式
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* 声明
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这些概念是大多数编程语言的基础。因为这些相似性，只要你通晓了一门编程语言，你可以通过对比差异来熟知另一门编程语言。
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另外一个学习新编程语言的好方法是开始编写一个简单标准的程序。它可以让你集中精力在语言上而非程序的逻辑本身。在这个系列的文章中，我们使用"猜数字"程序来实现，计算机会选择一个介于 1 到 100 之间的数字，并要求你来猜测它。程序会循环执行，直到您正确猜出该数字为止。
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"猜数字"这个小程序使用了编程语言的以下概念：
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* 变量
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* 输入
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* 输出
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* 条件判断
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* 循环
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这是一个学习新编程语言的绝佳实践。
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### 猜数字的 Elixir 实现
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[Elixir][2] 是一门被设计用于构建稳定可维护应用的动态类型函数式编程语言。它与 [Erlang][3] 运行于同一虚拟机之上，吸纳了 Erlang 的众多长处的同时拥有更加轻便的语法。
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你可以编写一个 Elixir 版本的"猜数字"游戏来体验这门语言。
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这是我的实现方法：
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```
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defmodule Guess do
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def guess() do
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random = Enum.random(1..100)
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IO.puts "Guess a number between 1 and 100"
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Guess.guess_loop(random)
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end
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def guess_loop(num) do
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data = IO.read(:stdio, :line)
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{guess, _rest} = Integer.parse(data)
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cond do
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guess < num ->
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IO.puts "Too low!"
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guess_loop(num)
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guess > num ->
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IO.puts "Too high!"
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guess_loop(num)
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true ->
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IO.puts "That's right!"
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end
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end
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end
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Guess.guess()
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```
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Elixir 通过列出变量的名称后面跟一个`=`号来为了给变量分配一个数值。举个例子，表达式 `random = 0` 给 `random` 变量分配一个数值 0。
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代码以定义一个 **module** 开始。在 Elixir 语言中，只有 module 可以包含非匿名函数。
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紧随其后的这行代码定义了入口函数 `guess()`，这个函数：
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* 调用 `Enum.random()` 函数来获取一个随机数
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* 打印游戏提示
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* 调用循环执行的函数
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剩余的游戏逻辑实现在 `guess_loop()` 函数中。
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`guess_loop()` 函数利用[尾递归 ][4] 来实现循环。Elixir 中有好几种实现循环的方法，尾递归是比较常用的一种方式。`guess_loop()` 函数做的最后一件事就是调用自身。
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`guess_loop()` 函数的第一行读取用户输入。下一行调用 `parse()` 函数将输入转换成一个整数。
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`cond` 表达式是 Elixir 版本的多重分支表达式。与其他语言中的 `if/elif` 或者 `if/elsif` 表达式不同，Elixir 对于的首个分支或者最后一个没有分支并没有区别对待。
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`cond` 表达式有三路分支：猜测的结果可以比随机数大、小或者相等。前两个选项先输出不等式的方向然后递归调用 `guess_loop()`，循环返回至函数开始。最后一个选项输出 `That's right`，然后这个函数就完成了。
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### 输出例子
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现在你已经编写了你的 Elixir 代码，你可以运行它来玩"猜数字"的游戏。每次你执行这个程序，Elixir 会选择一个不同的随机数，你可以一直猜下去直到你找到正确的答案：
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```
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$ elixir guess.exs
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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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30
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Too high
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20
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Too high
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10
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Too low
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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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"猜数字"游戏是一个学习一门新编程语言的绝佳入门程序，因为它用了非常直接的方法实践了常用的几个编程概念。通过用不同语言实现这个简单的小游戏，你可以实践各个语言的核心概念并且比较它们的细节。
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你是否有你最喜爱的编程语言？你将怎样用它来编写"猜数字"这个游戏？关注这个系列的文章来看看其他你可能感兴趣的语言实现。
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/20/12/elixir
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作者：[Moshe Zadka][a]
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选题：[lujun9972][b]
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译者：[tt67wq](https://github.com/tt67wq)
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校对：[校对者ID](https://github.com/校对者ID)
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||||
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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/dice_tabletop_board_gaming_game.jpg?itok=y93eW7HN (A die with rainbow color background)
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[2]: https://elixir-lang.org/
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[3]: https://www.erlang.org/
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[4]: https://en.wikipedia.org/wiki/Tail_call
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