[Boost-users] [boost.test] floating point comparison with user defined type

Subject: [Boost-users] [boost.test] floating point comparison with user defined type
From: Georgios Sermaidis (g.sermaidis_at_[hidden])
Date: 2018-03-20 22:46:17

Hello,

I have created a class to represent the euro currency and I am trying to use boost.test to check if two euro amounts are sufficiently close. I was expecting the following to pass the test given the tolerance level I have set, but instead it fails.
What is the proper way to compare two user-defined decimals? Thank you for your time.

#define BOOST_TEST_MODULE My Test
#include <boost/test/included/unit_test.hpp>

class eur {

    long double m_amount;

public:

    eur(long double amount)
    : m_amount(amount){}

    bool operator ==(const eur& rhs) const {
        return m_amount == rhs.m_amount;
    }

    bool operator !=(const eur& rhs) const {
        return m_amount != rhs.m_amount;
    }

    friend std::ostream& operator <<(std::ostream& os, const eur& rhs);
};

std::ostream& operator <<(std::ostream& os, const eur& rhs) {
    os << "EUR " << rhs.m_amount;
    return os;
}

BOOST_TEST_DECORATOR(* boost::unit_test::tolerance(eur(0.1)))

BOOST_AUTO_TEST_CASE(first_test)
{
    eur x(1.1);
    eur y(1.2);

    BOOST_TEST(x == y);
}