C++17 STL Cookbook

How to do it...

We are going to implement a program that does multiple different things concurrently but instead of explicitly starting threads, we use std::async and std::future:

1. First, we include all necessary headers and declare that we use the std namespace:

      #include <iostream>      #include <iomanip>      #include <map>      #include <string>      #include <algorithm>      #include <iterator>      #include <future>            using namespace std;

2. We implement three functions which have nothing to do with parallelism but do interesting tasks. The first function accepts a string and creates a histogram of all characters occurring within that string:

      static map<char, size_t> histogram(const string &s)      {          map<char, size_t> m;                for (char c : s) { m[c] += 1; }                return m;