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