If you are interested, I can explain it to you over vchat, it's way too involved to get into here. :)

I think we actually need to pass a name and environment.

`func <- exprToFunction(expr, name="func", assign.env=environment())`

@jmcphers, we balked from this because of having two environments as parameters, but `delayedAssign` does this and I found it pretty intuitive personally. (Annoyingly, we probably need to keep the signature backwards compatible though.)