- | SimplDontFoldBackAppend
- -- we fold `foldr (:)' back into flip (++),
- -- but we *don't* want to do it when compiling
- -- List.hs, otherwise
- -- xs ++ ys = foldr (:) ys xs
- -- {- via our loopback -}
- -- xs ++ ys = xs ++ ys
- -- Oops!
- -- So only use this flag inside List.hs
- -- (Sigh, what a HACK, Andy. WDP 96/01)
-