Thanks, I'll check out Data and Typeable
--- On Thu, 10/1/09, Brandon S. Allbery KF8NH wrote:
From: Brandon S. Allbery KF8NH
Subject: Re: [Haskell-cafe] Introspection on types.
To: "Gregory Propf"
Cc: "Brandon S. Allbery KF8NH" , "Haskell-Cafe"
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] allbery@kf8nh.comsystem administrator [openafs,heimdal,too many hats] allbery@ece.cmu.eduelectrical and computer engineering, carnegie mellon university KF8NH
