std::ratio for amendments

ratio.cpp

// Example for comment in PR 3428: https://github.com/ripple/rippled/pull/3428

#include <iostream>
#include <ratio>

constexpr int oldN = 204;
constexpr int oldD = 256;

constexpr int newN = 80;
constexpr int newD = 100;

std::ratio<oldN, oldD> const pre3396;
std::ratio<newN, newD> const post3396;

int main(int argc, char **argv)
{
    std::cout << " pre: "<< pre3396.num << " / " << pre3396.den << "\n";

    for (int i = 0; i < 100000; ++i)
    {
        auto x = (i * oldN) / oldD;
        auto y = (i * pre3396.num) / pre3396.den;

        if (x != y)
            std::cout << i << ": old=" << x << ", new=" << y << "\n";
    }

    std::cout << "post: " << post3396.num << " / " << post3396.den << "\n";

    for (int i = 0; i < 100000; ++i)
    {
        auto x = (i * newN / newD);
        auto y = (i * post3396.num) / post3396.den;

        if (x != y)
            std::cout << i << ": old=" << x << ", new=" << y << "\n";
    }

    return 0;
}