You are just saying the equally wrong thing on the opposing side. You can get to 2x without giving up anything. Lists are just a data structure. So are vecto

You are just saying the equally wrong thing on the opposing side. You can get to 2x without giving up anything. Lists are just a data structure. So are vectors. You don't give anything up to choose one or the other, you pick the right one and use it. You do not write "everything in procedural (by monads) way" to gain performance. Do notation is literally syntactic sugar, and there is no "perform faster" monad to do it in. Haskell code gets to 2x C speeds the same way C gets to 1x C speeds: profile your code and fix the inefficiencies.