On Tue, Sep 30, 2014 at 1:52 PM, Doug McIlroy <doug@cs.dartmouth.edu> wrote:
Ghci complains, "Could not deduce (Show a) arising from
the superclasses of an instance declaration from the
context (Num a)". Yet Show is a superclass of Num.
Hugs accepts the code.

Show used to be a superclass of Num. It's not in current ghc, and will probably be removed from the next version of the language standard.

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