Re: SICP Chapter 2, Footnote 3


> Regarding your original question, note that a procedure can well be
> called without using its name directly.
>
> (define (foo callback)
> .... (callback) ...)
>
> (define (my-func) ...)
> (trace my-func)
> (foo my-func)
>
> If we want to see all the places where my-func is called, the tracing
> must also be activated from inside foo. This is much easier to
> accomplish if the my-func _procedure_ is specially tagged instead of
> the variable that is bound to it.

That's a good point. I tested that explicitly in UCB Scheme after
reading your post and would guess that it's doing something more
sophisticated and harder to implement since it behaves as I expect and
want it to..

(define combine cons)
(define (dummy-test fn val1 val2)
(fn val1 (fn val2 '())))

STk>(trace combine)
okay
STk>(dummy-test cons 1 2)
(1 2)
STk>(dummy-test combine 1 2)
[4 lines of trace output]
(1 2)

The SICP footnote may not have been accounting for these types of
implementations. I'm glad, however, that UCB Scheme works in this
fashion; it makes my life easier. :-)

.

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