[gambit-list] limiting trace

Code:

~/code/irc$ cat trace.scm (define (foo x) x)

(define (bar) (foo 0))

(define (test) (foo 1) (bar))

(trace foo)

(test) ~/code/irc$ gsi trace.scm | > (foo 1) | 1 | > (foo 0) | 0

Problem:

Can I control trace where I can say "trace foo, but not when it's called by bar".

I.e. rather than just saying "trace this function", I would like to be able to say:

(trace foo predicate)

where predicate is a function that takes as input the "stack" frame, and as output creates a #t / #f, which decides whether this particular trace should be printed

On a side note -- all the cool debugging functions in Gambit -- is this part of the 100K LOC scheme or 50K LOC hand written C? (hoping it's the former)