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 [email protected] • http://www.joachim-breitner.de/ Jabber: [email protected] • GPG-Key: 0xF0FBF51F Debian Developer: [email protected]
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