[racket] Trace rejects set!

At Mon, 10 Oct 2011 10:31:39 -0700 (PDT),
michael rice wrote:
> 
> Welcome to DrRacket, version 5.1.3 [3m].
> Language: racket; memory limit: 128 MB.
> > (trace next-leaf-generator)
> set!: cannot modify a constant: next-leaf-generator

Try adding `(trace next-leaf-generator)' to the program itself, that
should work.

The interactions window is not part of the program, which is in its
own module. Since you can't mutate variables except in the module
where they're defined, you can't add tracing from the interactions
window.

Vincent