lib/Catch2/src/catch2/catch_approx.cpp

//              Copyright Catch2 Authors
// Distributed under the Boost Software License, Version 1.0.
//   (See accompanying file LICENSE.txt or copy at
//        https://www.boost.org/LICENSE_1_0.txt)

// SPDX-License-Identifier: BSL-1.0
#include <catch2/catch_approx.hpp>
#include <catch2/internal/catch_enforce.hpp>
#include <catch2/internal/catch_reusable_string_stream.hpp>

#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 {

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

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

    Approx Approx::operator-() const {
        auto temp(*this);
        temp.m_value = -temp.m_value;
        return temp;
    }


    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(std::isinf(m_value)? 0 : m_value)));
    }

    void Approx::setMargin(double newMargin) {
        CATCH_ENFORCE(newMargin >= 0,
            "Invalid Approx::margin: " << newMargin << '.'
            << " Approx::Margin has to be non-negative.");
        m_margin = newMargin;
    }

    void Approx::setEpsilon(double newEpsilon) {
        CATCH_ENFORCE(newEpsilon >= 0 && newEpsilon <= 1.0,
            "Invalid Approx::epsilon: " << newEpsilon << '.'
            << " Approx::epsilon has to be in [0, 1]");
        m_epsilon = newEpsilon;
    }

namespace literals {
    Approx operator ""_a(long double val) {
        return Approx(val);
    }
    Approx operator ""_a(unsigned long long val) {
        return Approx(val);
    }
} // end namespace literals

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

} // end namespace Catch