Re: [Haskell-cafe] Factoring into type classes

2009/1/19 Luke Palmer :

On Mon, Jan 19, 2009 at 3:58 AM, Patai Gergely wrote:

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However, there are other type classes that are too general to assign such concrete uses to. For instance, if a data structure can have more than one meaningful (and useful) Functor or Monoid instance,

As a side curiosity, I would love to see an example of any data structure which has more than one Functor instance. Especially those which have more than one useful functor instance. Luke

The recent, and great, blog post about moniods [1] discusses the fact that (Num a) could be one of several different monoids and how that was handled. [1] http://sigfpe.blogspot.com/2009/01/haskell-monoids-and-their-uses.html