Python-based monads essay (Re: Assignment versus binding)

[Gregory Ewing]

Steven D'Aprano wrote:
> "the implementation is free to use in-place mutations of the state object – 
> ... without letting anyone know that the implementation has given up 
> any functional purity."

If it's impossible to tell that functional purity has
been given up, then in what sense has it been given up
at all?

-- 
Greg