metis_tac: proper context (ProofContext.init it *not* sufficient);
simplified method setup;
structure HOL =
struct
type 'a eq = {eq : 'a -> 'a -> bool};
fun eq (A_:'a eq) = #eq A_;
end; (*struct HOL*)
structure List =
struct
fun member A_ x (y :: ys) = HOL.eq A_ x y orelse member A_ x ys
| member A_ x [] = false;
end; (*struct List*)
structure Codegen =
struct
fun collect_duplicates B_ xs ys (z :: zs) =
(if List.member B_ z xs
then (if List.member B_ z ys then collect_duplicates B_ xs ys zs
else collect_duplicates B_ xs (z :: ys) zs)
else collect_duplicates B_ (z :: xs) (z :: ys) zs)
| collect_duplicates B_ xs ys [] = xs;
end; (*struct Codegen*)