Hi Twan,

Getting rid of the requirement for FlexibleInstances should not be to
hard (nor should adding support for them to Yhc).

Sometimes adding support for things to Yhc is harder than you might
naturally think...

But even if I work
around that, this patch relies quite havilly on the mtl, which uses
multi parameter type classes and functional dependencies. Those might be
a bigger problem. Hoever the mtl was already used in other parts of the
compiler...

There are two parts of the mtl - one provides monads, one provides
monad transformers. In general the monad half is Haskell 98, the
transformer half is not - we've been careful to stick to the monad
half so far. The mtl is actually being split soon into a Haskell 98
half and a MPTC/FD half.

How much of the transformer side do you use, and how hard would it be
to remove that? From my limited knowledge of mtl, I believe you can
write your own custom instance for any given combination - which
removes the type class requirement. If that is so, that may be an
option.

Thanks

Neil
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