[Haskell-beginners] Type unions

[Guofeng Zhang]

What does "$" mean in Left $ A x. Why does not write it as "Left A x"?

For putStrLn $ "welcome", is the "$" has the same meaning as that in Left $
A x?


On Wed, Dec 15, 2010 at 4:26 AM, Russ Abbott <russ.abbott at gmail.com> wrote:

> Isn't "Either" the same thing as AorB in
>
> data AorB = Aconstructor Int | Bconstructor Int
>
>
> I want two separate types A and B along with a third type which is their
> Union. Is that not possible?
>
> In my actual case, I have more than two types.  So I would like a way to
> take the union of an arbitrarily number of types.
>
> data Union = A1 | A2 | ...
>
>
> where each of A1, A2, ... has its own data declaration.
> *
> -- Russ *
>
>
> On Tue, Dec 14, 2010 at 12:14 PM, Tobias Brandt <tob.brandt at googlemail.com
> > wrote:
>
>> data AorB = Aconstructor Int | Bconstructor Int
>
>
>
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