I'm not sure why I'm struggling to express myself here. I'm not saying Nix was wrong not to focus on optimising this; it's not likely to be their bottleneck. I'

I'm not sure why I'm struggling to express myself here. I'm not saying Nix was wrong not to focus on optimising this; it's not likely to be their bottleneck. I'm saying that the article's argument doesn't hold. Consider a case where somebody is using C++ for mobile OS portability or to hook into another large project, rather than the performance it offers. In that case, the argument that the parser would be equally fast in Haskell is irrelevant because that was never the use-case. Consider a case where somebody is using C++ for performance. In that case, the argument that the parser would be equally fast in Haskell is irrelevant because that's not the part that needs to be fast. The only time "X in Haskell is equally fast to X in C++" is an argument that you care about is when you care about the performance of X, and in that case the code wouldn't look like this.