Python宏:用例? [英] Python Macros: Use Cases?

问题描述

如果Python具有类似于Lisp/Scheme的宏功能(例如 MetaPython ) ，您将如何使用它?

If Python had a macro facility similar to Lisp/Scheme (something like MetaPython), how would you use it?

如果您是Lisp/Scheme程序员，那么您将使用什么类型的宏(除了在Python中具有清晰的句法并行性(例如while循环)的宏之外)?

If you are a Lisp/Scheme programmer, what sorts of things do you use macros for (other than things that have a clear syntactic parallel in Python such as a while loop)?

推荐答案

一些Lisp宏示例:

• ITERATE ，它是一种有趣且可扩展的循环工具
• CL-YACC / CL-WHO ，它可以指定带有静态和动态部分的html文档
• Parenscript 这是一个JavaScript代码生成器
• 各种简单的代码包装器，例如错误处理程序(我有一个with-gtk-error-message-handler，它执行代码并在发生未处理的错误时显示GtkMessageDialog)，执行程序(例如，给定代码，以不同的方式执行它线程；我有一个在主线程内的宏，可以在不同线程中执行代码； PCall 库使用宏包装要同时执行的代码)
• 具有宏的GUI构建器(例如，指定窗口小部件层次结构和窗口小部件的属性，并使用宏生成用于创建所有窗口小部件的代码)
• 在编译期间使用外部资源的代码生成器.例如，处理C标头并生成FFI代码的宏，或根据数据库模式生成类定义的宏
• 声明性FFI.例如，指定外部结构，函数，它们的参数类型并具有宏以生成相应的lisp结构，具有类型映射和封送处理代码的函数
• Common Lisp的基于连续性的Web框架使用宏将代码转换为CPS(连续传递样式)形式.

• ITERATE which is a funny and extensible loop facility
• CL-YACC/FUCC that are parser generators that generate parsers at compile time
• CL-WHO which allows specifying html documents with static and dynamic parts
• Parenscript which is a javascript code generator
• Various simple code-wrappers, e.g., error handlers (I have a with-gtk-error-message-handler that executes code and shows GtkMessageDialog if unhandled error occurs), executors (e.g., given a code, execute it in different thread; I have a within-main-thread macro that executes code in different threads; PCall library uses macros to wrap code to be executed concurrently)
• GUI builders with macros (e.g., specify widgets hierarchy and widgets' properties and have a macro generate code for creation of all widgets)
• Code generators that use external resources during compilation time. E.g., a macro that processes C headers and generates FFI code or a macro that generates classes definitions based on database schema
• Declarative FFI. E.g., specifying the foreign structures, functions, their argument types and having macros to generate corresponding lisp structures, functions with type mapping and marshaling code
• Continuations-based web frameworks for Common Lisp use macros that transform the code into CPS (continuation passing style) form.

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