[Haskell-cafe] Defining a containing function on polymorphic list
miguelimo38 at yandex.ru
Mon Dec 22 13:55:27 EST 2008
On 22 Dec 2008, at 17:35, Raeck Zhao wrote:
> But I just found another 'problem', I just realize that the list
> does not support the user-defined data type?
Don't worry, it does.
> the list is also depending on the Eq function?
No, it doesn't.
> data Shape = Square | Triangle | Circle
> [Square, Triangle, Circle]
Should work fine.
> Square == Square
Wouldn't work unless you declare your type "Shape" an instance of
class "Eq" - which can be done automatically.
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