> I'm not sure how purely functional it is ECS systems overlap functional programming (FP) only in that both are data first. Purely functional would mean neve

> I'm not sure how purely functional it is ECS systems overlap functional programming (FP) only in that both are data first. Purely functional would mean never mutating an existing value, functions only receiving one value and returning another, monadically binding side effects and so on. To put it bluntly, a non-trivial computer game in pure FP would hog every resource in your system to barely hit single digit frame rates. (Disclaimer: I love FP, and use it at my day job. It is not fit for games though)