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“覃学苦练（八）：Mathematica编程中程序包的定义与使用”
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Dear, this is LearningYard Academy.
Today, the editor brings you an article"Qin Xue's hard training (8): The Definition and Use of Package in Mathematica Programming "
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一、思维导图（Mind mapping）
二、程序包（Package）
Mathematica编程中的程序包就是一些功能相近的函数语句的集合，按照某种方式组合起来以便用户使用，相当于面向对象程序设计中的类。当使用时，系统会自动加载一些软件包，可以通过“$Packages”系统变量知道哪些程序包已经被加载，通过系统变量“$Path”知道这些程序包的位置。如下图所示：
A package in Mathematica programming is a collection of functional statements with similar functions, which are combined in some way for users to use, equivalent to a class in object-oriented programming. When using, the system will automatically load some packages. You can know which packages have been loaded through the " $Packages" system variable, and know the location of these packages through the " $Path" system variable. As shown in the following figure:
三、程序包的自定义（Customization of the package）
1、新建Wolfram语言程序包（New Wolfram Language Package）
打开Mathematica软件，在菜单栏中选择“文件”，选择“新建”然后选择“程序包\脚本”在其中选择“Wolfram语言程序包”就新建了一个Wolfram语言程序包。可以自己命名程序包名称，以便后续引入使用程序。
Open the Mathematica software, select "File" in the menu bar, select "New" and then select "Package \ Script", and select "Wolfram Language Package" to create a new Wolfram Language Package. You can name the package name yourself so that you can use it later.
在程序包定义结构中，BeginPackage[“程序包名称”]与EndPackage[]定义程序包的上下文，Begin[“Private`”]与End[]设置了当前环境上下文。通过以上设置上下文来区别不同环境下的同名变量，若特定的名字出现在一个上下文中，则没必要明确上下文的名字了。程序包中通过f::usage语句定义函数f的使用信息，对函数进行描述和用法说明。
In the package definition structure, BeginPackage [ "PackageName"] and EndPackage [] define the context of the package, and Begin [ "Private`"] and End [] set the current environment context. Variables with the same name in different environments can be distinguished by setting the context above. If a specific name appears in a context, there is no need to specify the name of the context. The package defines the usage information of the function f through the f: usage statement, and describes the function and its usage.
四、程序包的使用（Use of packages）
1、程序包导入（Package import）
当程序定义完成后，点击保存，可自由保存到自己想保存的位置，然后在Mathematica的笔记本窗体可使用Get[“文件浏览器”]选择自己保存的程序包位置导入程序包执行其中代码。
After the program definition is completed, click Save to freely save to the location you want to save, and then use Get [ "File Browser"] to select the location of the package you want to save in the notebook form of Mathematica to import the package and execute the code.
2、编程实例（Programming example）
根据以上阐述，小编通过一道简单实例来给大家演示一下全过程的操作。实例：生成一个软件包，用来求矩形的面积和周长。如下图所示：
According to the above elaboration, Xiaobian demonstrates the operation of the whole process through a simple example. Example: Generate a package to find the area and perimeter of a rectangle. As shown in the following figure:
在程序自定义输入时可用快捷键“Ait+Enter”新建一个Cell；并可通过“Definition[f]”函数或“？f”来查看自定义函数的信息。
You can use the shortcut key "Ait + Enter" to create a new Cell during the custom input of the program, and you can use the "Definition [f]" function or "? F "to view the information of the custom function."
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参考资料：
翻译：讯飞星火翻译，《Mathematica基础及其在数学建模中的应用》
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文案：qin
排版：qin
审核|Yue