Lambda-Over-Lambda在C ++中14 [英] Lambda-Over-Lambda in C++14

问题描述

如何递归lambda调用结束/终止？

How following recursive lambda call ends/terminates ?

#include <cstdio>

auto terminal = [](auto term)            // <---------+  
{                                        //           |
    return [=] (auto func)               //           |  ???
    {                                    //           |
        return terminal(func(term));     // >---------+
    };
};


auto main() -> int
{
    auto hello =[](auto s){ fprintf(s,"Hello\n"); return s; };
    auto world =[](auto s){ fprintf(s,"World\n"); return s; };


    terminal(stdout)
            (hello)
            (world) ;

    return 0;

}

我在这里缺少什么？

^运行代码

推荐答案

这不是一个递归函数调用， / p>

It's not a recursive function call, look at it step-by-step:

1. terminal（stdout） - 这只是返回一个已捕获 stdout


2. 使用lambda hello 调用1.的结果， lambda（ func（term）），其结果传递到 terminal（）如1中所示。


3. 使用lambda world 调用2.的结果，它与2相同，返回值被舍弃...

1. terminal(stdout) - this simply returns a lambda which has captured stdout
2. The result of 1. is called with the lambda hello, which executes the lambda (func(term)), the result of which is passed to terminal(), which simply returns a lambda as in 1.
3. The result of 2. is called with the lambda world, which does the same as 2, this time the return value is discarded...

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