11.4 Example

This section shows an example of tracing two functions and examining the output.

Define the following functions:

(defun foo (x y) (bar y x))
 
(defun bar (x y) (values (vector x y) (list y x)))

in a Listener and start the Tracer tool. The trace these functions by entering foo into the Trace pane of the Tracer and pressing Return or clicking the button. Notice that the symbol name appears in the Traced Functions: area.

Do the same for bar.

For longer function names, you might find it useful to type just a few characters and then press Up or Down to invoke in-place completion.

Then call:

(foo 100 200)

in the Listener. You will see output something like this printed in the Listener.

CL-USER 1 > foo 100 200
0 FOO > ...
  >> X : 100
  >> Y : 200
  1 BAR > ...
    >> X : 200
    >> Y : 100
  1 BAR < ...
    << VALUE-0 : #(200 100)
    << VALUE-1 : (100 200)
0 FOO < ...
  << VALUE-0 : #(200 100)
  << VALUE-1 : (100 200)
#(200 100)
(100 200)
 
CL-USER 2 >

Note: the format of the output is affected by the value of *trace-verbose*.

Now switch to the Output Text view of the Tracer and you will similar output.

Now switch to the Output Data view of the Tracer, which will looks like this:

The node that is labeled Arguments 100 200 contains the arguments to the function foo. Double-click on this node to show those arguments in an Inspector.

The first node that is labeled Values #(200 100) (100 200) contains the values returned by bar. Expand this node to reveal the two values. Double-click on one of the values nodes to inspect it. You can also see that these values were in turn returned by foo, as shown by the second node that is labeled Values #(200 100) (100 200).