Thanks, I'll check out Data and Typeable --- On Thu, 10/1/09, Brandon S. Allbery KF8NH <[email protected]> wrote:
From: Brandon S. Allbery KF8NH <[email protected]> Subject: Re: [Haskell-cafe] Introspection on types. To: "Gregory Propf" <[email protected]> Cc: "Brandon S. Allbery KF8NH" <[email protected]>, "Haskell-Cafe" <[email protected]> Date: Thursday, October 1, 2009, 6:14 PM On Oct 1, 2009, at 19:22 , Gregory Propf wrote:Is there a way to tell, let's say, how many constructors there are for a type? Or do I need one of the haskell extensions I've read about? If the constructors are nullary (that is: data MyData = Foo | Bar | Baz) you could derive Enum and Bounded, then (maxBound :: MyData) is one less than the number of constructors. Anything more complicated requires deriving Data or Typeable (I've done it with the latter but don't recall details off the top of my head). -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [email protected] administrator [openafs,heimdal,too many hats] [email protected] and computer engineering, carnegie mellon university KF8NH
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