[Haskell-cafe] Re: Strange typing?
ozgurakgun at gmail.com
Mon Mar 22 11:49:57 EDT 2010
Thank you all very much for the pointers.
On 22 March 2010 09:32, Gleb Alexeyev <gleb.alexeev at gmail.com> wrote:
> Ozgur Akgun wrote:
>> Is there any way to limit a functions type, not by a data type but by a
>> group of constructors of a data type? If not, what would be the *right*
>> thing to do to achieve this level of type safety?
>> data DT1 = X | Y | Z
>> data DT2 = A | B | C | D
>> func1 :: DT1 -> DT2 -- instead of this
>> func1' :: (X|Y) -> (B|C) -- i want sth. like this. (| means or)
>> OCaml has a feature called 'polymorphic variants' that allows exactly
> this. You may want to google 'polymorphic variants in haskell'.
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