This seems unintended. Maybe others are wise to the contrary? Perhaps a
patch should be made.
Thanks
On Mon, Apr 13, 2020, 1:57 PM Christiaan Baaij
Hello list,
Is the following behavior intended? or an oversight?
Prelude Control.DeepSeq> tail ((undefined :: ()) `seq` 1 : []) *** Exception: Prelude.undefined CallStack (from HasCallStack): error, called at libraries/base/GHC/Err.hs:80:14 in base:GHC.Err undefined, called at <interactive>:5:8 in interactive:Ghci2 Prelude Control.DeepSeq> tail ((undefined :: ()) `deepseq` 1 : []) []
If you're wondering what's happening, there is a (builtin) fixity declaration for 'seq': infixr `seq` 0
But there isn't one for `deepseq`.
So
undefined `seq` 1 : []
is parsed as
undefined `seq` (1 : [])
while
undefined `deepseq` 1 : []
is parsed as
(undefined `deepseq` 1) : []
In a real-life use-case, changing `seq` to `deepseq` actually resulted in a (very unanticipated) space-leak for me. So again, is the lack of fixity declaration for deepseq intentional? or an accidental omission?
Best regards,
Christiaan
_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries