Hey David, For instance:
arity :: (Data a) => a -> Int > arity = length . gmapQ (const ()) > Cheers, Pedro On Thu, Jun 25, 2009 at 17:31, David Fox <[email protected]> wrote: > Is it possible to determine the arity of a value's constructor? > Suppose I have a value x of type > > data A = B Int | C > > They typeOf function returns its TypeRep, which contains its type > constructor, but I don't see how to decide whether that > constructor's arity is 0 or 1. If the type has field names > I can look at those using Data.Data.conFields and count them, > but if it doesn't I don't see how to do it. > > -david > > > _______________________________________________ > Haskell-Cafe mailing list > [email protected] > http://www.haskell.org/mailman/listinfo/haskell-cafe > >
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