use fmt::format() for error_stats output.

std::ostream &operator<<(std::ostream &out, const ErrorStats &stats)

std::ostream &operator<<(std::ostream &out, const ErrorStats &stats)

{

{

    const std::ios_base::fmtflags flags = out.flags();

    out << fmt::format("Average: {:10.3e} StdDev: {:10.3e} MaxErr: {:10.3e} @ item: {}",

    const std::streamsize width         = out.width(10);

                       stats.avg(), stats.dev(), stats.max(), stats.idx());

    const std::streamsize prec          = out.precision(3);

    return out;

    out << std::scientific << "Average: " << stats.avg() << " StdDev: " << stats.dev()

        << " MaxErr: " << stats.max();

    out.precision(prec);

    out.width(width);

    out.flags(flags);

    return out << " @ item: " << stats.idx();

}

}