Hi all - What's the best approach to determine free variables at source level? What i am trying to accomplish is to take a scheme expression from a file, say (+ foo bar) and transform (lambda (foo bar)   (+ foo bar)) for arbitrary scheme expressions.  Are there procedures that would allow me to determine whether a symbol has a binding?  Given scheme identifier can be bound to different values, it seems like this would require some sort of runtime environment inspection - is that true? Thanks, yc