polymorphic type in state of state monad

[Wang Meng]

Hi All,

Any one of your have the experience of defining a state of a state monad
as a polymorphic type?
I want to have:

> type State = Term a => [a]
> data M a = M (State -> IO(State,a))

GHC yields a error message "Illegal polymorphic type".
How to resolve this?

Thank you very much.
  
 -W-M-
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