我如何理解这个C类型声明？ [英] How can I make sense of this C type declaration?

问题描述

double (*bar(int, double(*)(double,double[])))(double);

在审查演讲幻灯片时，我发现有一个练习留给学生：

While reviewing a lecture slide, I found an exercise left to the student:

用简单的英语来说，此C声明中的 bar 是什么类型？

请帮助我完成此过程。我什至不知道从哪里开始，除了最终会返回双精度值。

Please help walk me through this. I don't even know where to begin, except that something is ultimately returning a double.

推荐答案

此答案带给您使用螺旋规则的能力。能够通过从未知元素开始并对其进行阅读来理解复杂的表达式（首先解决括号中的问题）。

This answer is brought to you by the ability to use the Spiral Rule. Being able to understand a complex expression by starting at the unknown element and reading around it (resolving things in the parenthesis first). A very useful skill when reading code.

        bar                                            - bar
        bar()                                          - is a function
        bar(int, )                                     - which takes an int...
        bar(int, (*)())                                - and a function pointer
        bar(int, double(*)())                          - which returns a double
        bar(int, double(*)(double, ))                  - and takes a double...
        bar(int, double(*)(double, double[]))          - and an array of doubles
      (*bar(int, double(*)(double, double[])))         - and returns a pointer
      (*bar(int, double(*)(double, double[])))()       - to a function
      (*bar(int, double(*)(double, double[])))(double) - taking a double
double(*bar(int, double(*)(double, double[])))(double) - which returns a double

那是har d方法...当然，有些站点使此操作变得容易，例如， cdecl 网站；但是即使您无法上网也能够读取代码。

That was the hard way... There are of course sites that make this easier, the cdecl site for example; but it's good to be able to read code even when you can't get to the internet.

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