Re: [Haskell-cafe] showing a user defined type

michael rice wrote on 19.05.2009 18:16:

Cool!

Is there *anything* Haskell *can't* do?

Well, I haven't found a way to emulate polymorphics kinds yet, and I feel like I need them. Other than than - probably no.

Michael

--- On *Mon, 5/18/09, David Menendez //* wrote:

From: David Menendez Subject: Re: [Haskell-cafe] showing a user defined type To: "Ryan Ingram" Cc: haskell-cafe@haskell.org Date: Monday, May 18, 2009, 10:26 PM

On Mon, May 18, 2009 at 10:02 PM, Ryan Ingram > wrote: > Unfortunately, you can't derive Show on Chain as defined, because it > contains a function:

Sure you can. I just tried the following, and it compiled without complaints.

> import Text.Show.Functions > > data Chain = Link Int (Int -> Chain) deriving (Show)

The usual warnings about orphan instances apply, but the purpose of the Text.Show.Functions module is to provide a standard Show instance for functions so that libraries (e.g., QuickCheck) don't declare conflicting instances.

-- Dave Menendez > <http://www.eyrie.org/~zednenem/ http://www.eyrie.org/%7Ezednenem/> _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

------------------------------------------------------------------------

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe