gistfile1.txt

#include <iostream>
#include <string>
#include <cassert>

constexpr int currency(const char *cc)
{
    return cc[0] | (cc[1] << 8) | (cc[2] << 16);
}

template<int CUR>
struct Money {
    double amount;

    Money(double amount) : amount(amount) {}

    Money<CUR> operator+(Money<CUR> other) {
        return Money<CUR>(this->amount + other.amount);
    }

    bool operator==(Money<CUR> other) {
        return this->amount == other.amount;
    }
};

int main(int,char**) {
    Money<currency("USD")> five_bucks(5);
    Money<currency("USD")> handful_of_dollars(4);
    Money<currency("EUR")> some_euros(3);
    assert(five_bucks + handful_of_dollars == Money<currency("USD")>(9));
    // error: no match for 'operator+' (operand types are 'Money<4477781>' and 'Money<5395781>')
    // assert(five_bucks + some_euros == Money<currency("USD")>(8)); 
}