[coolplants]

IMO I’d rather just write idiomatic C++ then non-idiomatic ghc-specific Haskell code if performance is important, and it nearly always is.

[whateveracct]

The thing is, like 20% of your program ends up being non-idiomatic, ghc-specific Haskell. I suppose for certain applications it could end up being the whole thing, but in general I'm thinking optimized Haskell is in that ballpark tops.

And idiomatic Haskell's performance is plenty acceptable for a variety of common use-cases (so not "nearly always is")

[coolplants]

In my experience that has not been the case. Either unacceptably slow computation or High memory usage.