[Haskell-cafe] Is it possible to represent such polymorphism?
Alberto G. Corona
agocorona at gmail.com
Wed Oct 5 13:45:56 CEST 2011
If a newbie considers this as something natural, this is another reason for
syntactic sugaring of HList:
http://www.haskell.org/pipermail/haskell-cafe/2011-April/090986.html
2011/10/2 Du Xi <sdiyazg at sjtu.edu.cn>
> --I tried to write such polymorphic function:
>
> expand (x,y,z) = (x,y,z)
> expand (x,y) = (x,y,1)
>
> --And it didn't compile. Then I added a type signature:
>
> expand::a->b
> expand (x,y,z) = (x,y,z)
> expand (x,y) = (x,y,1)
>
> --It still didn't compile. I think the reason is that the following is
> disallowed:
>
> f::a->b
> f x = x
>
> --Is it possible to get around this and write the "expand" function? Of
> course, x and y may be of different types
>
>
>
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