Class WithinRelMatcher

CvPlot/ext/catch2/inc/catch.hpp:3406–3413

Given IEEE-754 format for floats and doubles, we can assume that float -> double promotion is lossless. Given this, we can assume that if we do the standard relative comparison of |lhs - rhs| <= epsilon * max(fabs(lhs), fabs(rhs)), then we get the same result if we do this for floats, as if we do this for doubles that were promoted from floats.

        // the same result if we do this for floats, as if we do this for
        // doubles that were promoted from floats.
        struct WithinRelMatcher : MatcherBase<double> {
            WithinRelMatcher(double target, double epsilon);
            bool match(double const& matchee) const override;
            std::string describe() const override;
        private:
            double m_target;
            double m_epsilon;
        };

    } // namespace Floating