[Haskell-cafe] Unique functor instance

Luke Palmer lrpalmer at gmail.com
Tue Nov 25 07:40:37 EST 2008

I've been wondering, is it ever possible to have two (extensionally)
different Functor instances for the same type?  I do mean in Haskell;
i.e. (,) doesn't count.  I've failed to either come up with any
examples or prove that they all must be the same using the laws.


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