[Haskell-beginners] 'Iterating a data type'

Are there anyway to express the "iterating" of a user-defined data type in Haskell? For example, in

data Shape = Square | Circle | Triangle

how can I 'iterate' them and apply them all to the same function without indicating them explicitly? such as [func Square, func Circle, func Triangle]. Can I use a form similar to the following case in a list instead:

Numbers = [1,2,3,4,5]

[func x | x <- Numbers ]

Actually what I want is to obtain all the possible values of a data type (Shape). Thank you very much! Best wishes, Raeck