C++17 STL Cookbook

How to do it...

In this section, we define some simple toy function objects and concatenate them, so we get a single function that applies the simple toy functions after each other to the input we give it. In order to do so, we write our own concatenation helper function:

1. First, we need some includes:

      #include <iostream>      #include <functional>

2. Then, we implement the helper function, concat, which arbitrarily takes many parameters. These parameters will be functions, such as f, g, and h, and the result will be another function object that applies f(g(h(...))) on any input:

      template <typename T, typename ...Ts>      auto concat(T t, Ts ...ts)      {

 

3. Now, it gets a little complicated. When the user provides functions f, g, and h, we will evaluate ...