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You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Beginners digest..." Today's Topics: 1. Basic "data" question (Costello, Roger L.) ---------------------------------------------------------------------- Message: 1 Date: Thu, 24 Nov 2011 10:43:58 +0000 From: "Costello, Roger L." <coste...@mitre.org> Subject: [Haskell-beginners] Basic "data" question To: "beginners@haskell.org" <beginners@haskell.org> Message-ID: <b5fee00b53cf054aa8439027e8fe177518191...@imcmbx04.mitre.org> Content-Type: text/plain; charset="us-ascii" Hi Folks, I am trying to define a data type for this: A Lambda term is one of these: - Variable - Application of a Lambda term to a Lambda term - Abstraction of a Variable in a Lambda term Here's an example of a Lambda term: term = Abstraction (Variable X) (Application (Variable X) (Variable Y)) Is there a way to define Lambda term? Here's an attempt at defining it: data Var = V | W | X | Y | Z data Lambda = Variable Var | Application Lambda Lambda | Abstraction (Variable Var) Lambda But that yields the following error: test.hs:5:71: Not in scope: type constructor or class 'Variable' Any suggestions would be much appreciated. /Roger ------------------------------ _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 41, Issue 33 *****************************************