Number of procedure calls
In software-testing applications, it is useful to be able to count the number of times a given procedure is called during the course of a computation. Write a procedure
make-monitored
that takes as input a procedure,
f
, that itself takes one input. The result returned by
make-monitored
is a third procedure, say
mf
, that keeps track of the number of times it has been called by maintaining an internal counter. If the input to
mf
is the special symbol
how-many-calls?
, then mf returns the value of the counter. If the input is the special symbol reset-count, then
reset-count, mf
resets the counter to zero. For any other input,
mf
returns the result of calling
f
on that input and increments the counter. For instance, we could make a monitored version of the
sqrt
procedure:
(define s (make-monitored sqrt))
(s 100)
10
(s 'how-many-calls?)
1