[isabelle-dev] instantiation

[Florian Haftmann]

> :( I also failed a few weeks ago to instantiate the fold combinator to
> iterate function composition ...

Hmmm... perhaps "fold (op o) id id" is what you want in that case.

> But is this restriction fundamental or does it happen to be there?

Well, the type classes in Isabelle are an instance of order-sorted
algebra which demands type arguments to be free.  Perhaps it is possible
to relax this without smashing the meta theory (I don't know the
answer).  Anyway, this would mean a lot of work...

	Florian

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