The original example isn't really using ranges except to emulate C++98 iterator work though.

The actual equivalent might be something closer to:

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

Even that is enough to make ranges useful in my mind, but in a codebase which has started to integrate some functional programming techniques, there are also applications for things like views and transforms.

This can make it easier to reason about iteration pipelines in ways you might already be familiar with from POSIX.

That all said, it's C++ so sometimes the error messages get a lot more 'interesting' than they would have with STL-style iterators, especially when mixed with constexpr expressions as you might do with std::format or fmt libs.

The first one too? Isn't that the map-reduce fork-join golden example of multiprocessing?