inline double algorithm_call(std::span<double const> xs) noexcept {
        return std::accumulate(
            xs.begin(),
            xs.end(),
            0.0,
            [](double acc, double volts) {
                auto mv  = calibrated_mv(volts);
                auto err = residual(mv);
                return weighted_square(err) + acc;
        });
    }

    inline double raw_loop(std::span<double const> xs) noexcept {
        double sum = 0.0;

        for (double volts : xs) {
            auto mv  = calibrated_mv(volts);
            auto err = residual(mv);
            sum += weighted_square(err);
        }

        return sum;
    }

https://tiki.li/blog/lucky_code.html

> std::visit over std::variant<A, B, C> is lowered to a switch over the active alternative.

> In this case, layout is probably doing more work than the dispatch mechanism itself.

Very likely because last time I checked visit lowers to a virtual call.

There are proposals to introduce better exceptions into C++. Like this: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p07....

But until it's not in the standard, people should use std::expceted instead.

You want to see a beautiful compiler? Look at Plan 9’s compiler suite. A man could understand and even build on that.

Another name for compilers: invisible backdoor injectors. The more complex is the syntax the more it is likely to happen... I let you guess how the "sane" syntax from c++ and similar (LOL) does fit here...