You can get this information through the Data.Data module. There are two typeclasses which can be (have to be, I believe) derived for your data type, Data and Typeable. The Data class lets you access a representation of your type including type constructors. To set this up, you need to import Data.Data and enable the DeriveDataTypeable extension: {-# LANGUAGE DeriveDataTypeable #-} import Data.Data data Codes = A0100A | A0500A deriving (Show, Data, Typeable) Now you can get a representation of the type: λ> dataTypeOf (undefined :: Codes) DataType {tycon = "Main.Codes", datarep = AlgRep [A0100A,A0500A]} Since your type is an algebraic data type (AlgRep), the DataRep contains its constructors, which you can inspect with functions from the Data.Data module. On Mon, May 18, 2015 at 4:20 PM, Cody Goodman <codygman.consulting@gmail.com
wrote:
Can I use either template Haskell, GHC Generics, or something else to get the list of Constructors in Codes? Then I could do `map show codeSumTypeMembers` and get `["A0100A","A0500A"]`?
Here's an example of solving this problem manually:
data Codes = A0100A | A0500A deriving Show
codeExists "A0100A" = True codeExists "A0500A" = True codeExists _ = False
main = print $ codeExists xmlElementName where xmlElementName = "A0500A"
-- λ> main -- True _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe