Re: Use sharing in the Alternative instance of Maybe

15 Dec 2011

      Christian Maeder  writes:
...
Am 14.12.2011 13:17, schrieb Bas van Dijk:
...
On 14 December 2011 12:51, Michael Snoyman  wrote:
...
Out of curiosity, does this actually bypass an extra allocation, or is
GHC smart enough to notice the possibility to share?
With optimizations on, GHC seems to be smart enough. Since the
optimized core of:
plus1 Nothing  r = r
plus1 (Just x) _ = Just x
I suggest to directly write this using case:
l <|> r = case l of
   Nothing -> r
   Just _ -> l
Why not

 plus1 Nothing  r = r
 plus1 l@(Just x) _ = l

or the equivalent written with <|>?

-- 
Jón Fairbairn                                 Jon.Fairbairn@cl.cam.ac.uk

Re: Use sharing in the Alternative instance of Maybe

Jon Fairbairn