APIs and programming languages are UI for programmers, so yeah, they deserve some UX thinking. However, where is the current trend of functional programming in

APIs and programming languages are UI for programmers, so yeah, they deserve some UX thinking. However, where is the current trend of functional programming in this piece? (I am not disparaging FP, on the contrary, I think it's a good development.) Shouldn't API calls be, for example, easy to test? In functional programming, we often avoid doing actions directly, and instead give descriptions of actions (in form of functions) that are to be made. Does your API support that? What about minimization of the state that the API requires to keep, and its transparency? I am sorry if I come off a little incoherent. Best would be if I could give some tool a program that calls an API, say a sequence of API calls. And I would be told, this sequence is valid for the API. So I could prove for my program that it is accessing the API correctly.