6.5 Advising subfunctions

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6.5 Advising subfunctions

Subfunctions are functions that are defined inside the body of other functions rather than by top level defining forms like defun, defmethod, etc. To advise such a subfunction, call defadvice with a "subfunction dspec" of the form:

(subfunction sub-name parent-dspec)
(flet sub-name parent-dspec)
(labels sub-name parent-dspec)

See Subfunction dspecs for details. The rest of the defadvice form has the same effect as when advising ordinary functions.

The behavior when advising a subfunction is somewhat different from advising other functions.

defadvice modifies the parent of the subfunction such that future execution of the code that creates the subfunction will create it advised.
A subsequent call to defadvice with the same dspec and name re-modifies the parent, and also causes any of the subfunctions that were already created advised to change their "advice" behavior (as defined by the defadvice form) to the behavior specified by the latest call to defadvice.
remove-advice with the same dspec and name returns the parent function to its original state, and switches off the "advice" for the subfunctions that were created "advised".
Using defadvice again with the same dspec and name after remove-advice modifies the parent as in the first point above, but has no affect on any subfunction that was created by the parent before the call to remove-advice.

Advising of subfunction works only for compiled code.

6.5.1 Notes on subfunction names

Anonymous lambdas are named by the compiler using integers.

You can find the dspec of a given subfunction by calling object-dspec on the subfunction. You can also construct it from the printed representation of the subfunction, which contains the sub-name and the parent-dspec.

A subfunction can be given an name using a hcl:lambda-name declaration (see declare). If this is of the form (subfunction sub-name), then the dspec of the subfunction will be contain both sub-name and the correct parent-dspec. However, if it has any other form, then dspec will be that name and you will need to know the parent-dspec in order to construct the subfunction dspec.

LispWorks User Guide and Reference Manual - 20 Sep 2017