Re: [Haskell-beginners] Type unions

'$' has the same effect as parens around whatever's after it so 'Left $ A x' == 'Left (A x)'. Since Haskell is left associative 'Left A x' == '(Left A) x' which is wrong and gives me a compile error. And yes it has the same effect as putStrLn $ "welcome". -deech On Wed, Dec 15, 2010 at 8:15 AM, Guofeng Zhang wrote:

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 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 wrote:

...

data AorB = Aconstructor Int | Bconstructor Int

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