[Haskell-beginners] Re: [Haskell-cafe] 'Iterating a data type'
lrpalmer at gmail.com
Mon Dec 29 20:28:46 EST 2008
On Mon, Dec 29, 2008 at 6:24 PM, <raeck at msn.com> wrote:
> Are there anyway to express the "iterating" of a user-defined data type in
> 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
For "enum" style data, where all the constructors have no arguments, you can
do deriving (Bounded, Enum), so:
data Shape = Square | Circle | Triangle
numbers = [minBound..maxBound] :: [Shape]
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