adam.smyczek:
> Example:
>
> data SampleType = A | B Int | C String | D -- .... etc.
>
> sampleTypes = [A, B 5, C "test"] :: [SampleType]
>
> How do I find for example element A in the sampleTypes list?
> Do I have to create e.g.:
>
> isA :: SampleType -> Bool
> isA A = True
> isA _ = False
>
> for every constructor and use find?
> It feels like this is not the quicker method.
This is where the implicit filtering in a list comprehension comes in
really handy,
data T = A | B Int | C String | D
deriving Show
xs = [A, B 5, C "test", D]
main = do print [ A | A <- xs ] -- filter A's
print [ x | x@(C _) <- xs ] -- filter C's
{-
*Main> main
[A]
[C "test"]
-}
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