[Haskell-cafe] how to check thunk

[Kazu Yamamoto ( 山本和彦 )]

Hello,

Are there any ways to see if a value is a thunk or memorized?
I would like to have a function like:
  isThunk :: a -> IO Bool

I'm implementing some data structures described in "Purely Functional
Data Structures" and want to check my implementation is correct.
E.g.

	https://gist.github.com/2987425

Thanks.

--Kazu