[Haskell-beginners] Odd behavior from WinHugs
daniel.is.fischer at web.de
Wed Jan 14 16:07:06 EST 2009
Am Mittwoch, 14. Januar 2009 21:23 schrieb Conrad Meyer:
> On Wednesday 14 January 2009 11:46:23 am Justin Bailey wrote:
> > You have to capitalize your type names and data constructors:
> > data MyTuple a b c d = My4Tuple a b c d
> > | My3Tuple a b c
> > | My2Tuple a b
> > | My1Tuple a
> > deriving (Show)
> Also, I think (but by no means am I sure) that you should cut out 'a b c d'
> from the left side, i.e.:
> data MyTuple = My4Tuple a b c d
> | My3Tuple a b c
> | My2Tuple a b
> | My1Tuple a
> deriving (Show)
> Someone please tell me if I am wrong :).
The type variables are necessary on the left hand side, otherwise a
(My3Tuple x y z) could hold values of completely unknown type and so you
couldn't do anything useful with it.
If the types of things held weren't specified on the left, what type could
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