> I hope you're not suggesting that it's impossible to write this function without such constraints. To be concrete about it, that's exactly what I'm suggestin

> I hope you're not suggesting that it's impossible to write this function without such constraints. To be concrete about it, that's exactly what I'm suggesting. Please demonstrate, in any programming language, a derivative function that is parametrically polymorphic - that is, the same machine code will handle absolutely any type that's thrown at it - floating point, integral, string, function, map, set, graph, etc. I do not believe it's possible, unless you have some very different notion of derivative in mind. I would be delighted to learn it is possible, and mildly pleased to learn of a reasonable use of the phrase "derivative function" that's other than what I'm thinking and which makes sense of what you've written above.