Ok, will do. How about "in long?"  Why can't eval bind to an environment that encompasses the lexical closure I made? Mike <div>On 10/25/07, Chongkai Zhu <<a href="mailto:czhu@cs.utah.edu">czhu@cs.utah.edu</a>> wrote:<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Mike J. Bell wrote: > I don't think this is PLT specific, so I apologize if this should be > on a more general scheme list. > > I'm interested in adding a generic hook to evaluate a piece of code at > an arbitrary point in my program.  This would be useful for debugging > purposes.  For instance: > > (let ((x 5)) >   ;(do a bunch of stuff with x) >   (write (eval (read)))) > > Obviously this isn't very useful outside of a loop or other more > complicated idea, but this is just a toy to show the problem.  When > (read) runs, I would like to type in something like: > > (set! x 7) > > This doesn't work.  The error is that 'x' is unbound.  So I tried: > ... >   (write (eval (read) (interaction-environment)))) > > and that didn't work either.  It seems like I can't get to the > environment that contains the lexical closure created by the initial > (let...). > > Is there any way around this?  I supposed I could write my own (mini) > version of eval, but that seems pretty extreme.  How can I get access > to the lexical environment at the point (eval) is executed so I can > inject arbitrary code? In short, you can't. So try some other way to do the debug, say using the debug tool. > > Thanks for any tips!!! > > Mike > > -- > Mike J. Bell on gmail > ------------------------------------------------------------------------ > > _________________________________________________ >   For list-related administrative tasks: >   <a href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme">http://list.cs.brown.edu/mailman/listinfo/plt-scheme</a> > </blockquote></div> -- Mike J. Bell on gmail