> Yes that interface covers some edge cases that I've _never_ seen in practice (visiting two variants at once??), heh, this was literally one of my first uses

> Yes that interface covers some edge cases that I've _never_ seen in practice (visiting two variants at once??), heh, this was literally one of my first uses of C++ variants: that job needed a generic set of mathematical functions in a way that emulated a weaker type system (with automated conversions left and right), while preserving the original types as far as possible, and did meaningful conversions otherwise e.g. more-or-less using value = variant<int, float, string, vector<float>>; value clamp(value x, value a, value b);