Yes, in a non-pure type system, you are "on your honor" to not cause side effects. Clojure made STM a first-class language feature despite this https://clojure

Yes, in a non-pure type system, you are "on your honor" to not cause side effects. Clojure made STM a first-class language feature despite this https://clojure.org/reference/refs https://clojure.org/reference/refs Second, the problems with impurity you listed are exactly solved by Haskell. Just because "you cannnot port that to x/y/z" language should've be counted against the haskell language. We are talking about transactions here, but you're worried about thunks and memory allocations, and comparing this to java? It seems like you've simply decided Haskell is categorically slow, regardless of the context we're talking about.