[Haskell-cafe] SYB: extending a generic reader with a type class

[Sugar Bzzz]

Dear -cafe,

Is it possible to extend a generic reader (extR / ext1R from syb) with a
type class?


For example, let

foo :: (Integral a) => SomeMonad a

I could write:

reader = ... `extR` (foo :: SomeMonad Int) `extR` (foo :: SomeMonad Integer)

However, that is tedious.  Could I do something like

reader = ... `extR` foo

and have it apply to all instances of Integral?


I hope I am being clear.

Thank you.
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