Try passing a state object containing all the flags you need to keep track of that 30 or 60 frames a second. Hmm, have you tried it? I don't see an immediate p

Try passing a state object containing all the flags you need to keep track of that 30 or 60 frames a second. Hmm, have you tried it? I don't see an immediate problem. 60 Hz is not an immense rate for computers. And state updates don't usually involve copying large structures, since pure languages use lots of sharing. It's more like updating a tree; you just do some logarithmic amount of consing. There aren't that many companies using Haskell at all, so you can't infer much from the fact that there aren't many large-scale games written in it. This is of course not an argument, but John Carmack doesn't seem to believe purity itself is an intractable performance problem!