| > Anyway, as I am still wondering why ghc creates different code for | > returnP a = return a | > returnP = return | > | | Ah, now I rember this coming up before. | | Simon, is this a CAF issue? Or did it trigger the -fno-state-hack case? I'm not sure. A small example would be good. | I've definitely run into the odd other case where point-freeing | a bit of code messes with the complexity. That should not happen -- except for the state-hack. Which is this: Consider f1 :: Char -> IO () f1 = \c. let i = ord c in \s. print i s Here s::State World. Is this equivalent to f2 = \c.\s. print (ord c) s The latter is very much more efficient than 'f1', because it doesn't build an intermediate lambda. This matters a lot in I/O-intensive programs. But if 'f' is called thus: forever (f 'w') then (ord 'w') is computed once for each call of f2, but is shared among all calls to f1. And that can make a big difference too. I have no idea whether this is playing a role in the example you are discussing -- my guess is not, and there may be another performance bug lurking. So eliciting a small demo would be great. Simon