Hi Herbert, Am Sonntag, den 03.08.2014, 11:31 +0200 schrieb Herbert Valerio Riedel:
However, the following two functions are not equivalent after compilation to Core:
g, h :: (Int -> Int) -> Int -> () g f x = let !y = f x in () h f x = case f x of y -> ()
In fact, compilation results in
g = \ (f_asi :: Int -> Int) (x_asj :: Int) -> case f_asi x_asj of _ [Occ=Dead] { I# ipv_sKS -> () }
h = \ _ [Occ=Dead] _ [Occ=Dead] -> ()
Is the documentation inaccurate/incomplete/I-missed-something or is the implementation to blame?
I think that in Haskell (which is not Core!), a "case" does not imply evaluation – only if the patterns require it. So the example in the docs is correct (case e of [x,y] -> b requires evaluation of e), but your example is simply optimized away. haskell.org is down, so I can’t check if the report has anything to say about that. Greetings, Joachim -- Joachim “nomeata” Breitner mail@joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata@joachim-breitner.de • GPG-Key: 0xF0FBF51F Debian Developer: nomeata@debian.org