I don't have an answer, but would be extremely interested in knowing
one!
one of my first attempts to use GADTs was to do something similar,
implemening the simple polymorphic lambda calculus in a way that
transformations could be guarenteed typesafe statically, but then when I
went and tried to write an interpreter, I couldn't figure out how to
read in programs to interpret.
it seems you would want something like first class existentials 'Exp
(exists a . a)' or something like that.
John
--
John Meacham - ⑆repetae.net⑆john⑈
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