选择两个函数之间的函子 [英] Functor for Choosing Between Two Functions

问题描述

Googling for C ++函子语法带来了很多不同的结果，我不认为我看到任何需要。一些使用模板，一些使用单个类，其他多个，还有一些使用structs。我不知道我需要什么具体的元素我想做什么。所以现在，我想做什么：

Googling for C++ functor syntax brings a lot of different results and I don't think I see what need in any of them. Some use templates, some use a single class, others multiple, and still others use structs instead. I'm never sure what specific elements I need for what I want to do. So now, what I want to do:

我有两个功能。它们都采用完全相同的参数，但命名方式不同，并返回不同的结果，但返回类型也是相同的，例如

I have two functions. They both take the exact same parameters, but are named differently and will return a different result, though the return type is also the same, e.g.,

unsigned foo1（char * start，char * end）;

c>

unsigned foo1(char *start, char *end);
unsigned foo2(char *start, char *end);

我只想根据布尔变量的值来选择调用哪个函数。我可以写一个谓词来选择两者之间，但这似乎不是一个优雅的解决方案。如果这是C，我会使用一个简单的函数指针，但我已经被告知他们在C ++中不能很好地工作。

I just want to choose which function to call depending on the value of a Boolean variable. I could just write a predicate to choose between the two, but that doesn't seem an elegant solution. If this were C, I'd use a simple function pointer, but I've been advised they don't work well in C++.

编辑：

推荐答案

只需使用 std： ：function ：

std::function<unsigned int(char*, char*)> func = condition ? foo1 : foo2;
//            ^^^^^^^^^^^^^^^^^^^^^^^^^^ function signature

// ...

unsigned int result = func(start, end);

此外，函数指针在C ++中运行正常：

Also, function pointers work fine in C++:

auto func = condition ? foo1 : foo2;

unsigned int result = func(start, end);

但 std :: function 。

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