Catch2/include/internal/catch_approx.cpp

/*
 *  Created by Martin on 19/07/2017.
 *  Copyright 2017 Two Blue Cubes Ltd. All rights reserved.
 *
 *  Distributed under the Boost Software License, Version 1.0. (See accompanying
 *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 */

#include "catch_approx.h"

#include <cmath>
#include <limits>

namespace {

// Performs equivalent check of std::fabs(lhs - rhs) <= margin
// But without the subtraction to allow for INFINITY in comparison
bool marginComparison(double lhs, double rhs, double margin) {
    return (lhs + margin >= rhs) && (rhs + margin >= lhs);
}

}

namespace Catch {
namespace Detail {

    Approx::Approx ( double value )
    :   m_epsilon( std::numeric_limits<float>::epsilon()*100 ),
        m_margin( 0.0 ),
        m_scale( 0.0 ),
        m_value( value )
    {}

    Approx Approx::custom() {
        return Approx( 0 );
    }

    std::string Approx::toString() const {
        ReusableStringStream rss;
        rss << "Approx( " << ::Catch::Detail::stringify( m_value ) << " )";
        return rss.str();
    }

    bool Approx::equalityComparisonImpl(const double other) const {
        // First try with fixed margin, then compute margin based on epsilon, scale and Approx's value
        // Thanks to Richard Harris for his help refining the scaled margin value
        return marginComparison(m_value, other, m_margin) || marginComparison(m_value, other, m_epsilon * (m_scale + std::fabs(m_value)));
    }

} // end namespace Detail

std::string StringMaker<Catch::Detail::Approx>::convert(Catch::Detail::Approx const& value) {
    return value.toString();
}

} // end namespace Catch