[Haskell-cafe] Papers discussing interpreters for call by need?

I'm writing an interpreter for a call by need language and have been doing a direct implementation of the Launchbury semantics. My problem is that in the variable rule, an alpha conversion is done that, as far as I understand, is going to hinder any tail call optimization. I realize that the intent of Launchbury's paper is to come up with a theoretical framework for call by need, not to guide an implementation per say. Is anyone aware of any papers out there that go into detail on the construction of an actual interpreter? TIA, David -- David Sankel Sankel Software www.sankelsoftware.com 585 617 4748 (Office)