[Openmcl-devel] Am I failing to find documentation that exists?

Ron Garret ron at flownet.com
Tue Jun 15 09:06:04 PDT 2010

See contrib/garret/combination-hook.lisp for an example of how ADVISE can be used to modify the core semantics of the language.


On Jun 15, 2010, at 8:20 AM, Daniel Weinreb wrote:

> I couldn't find any documentation of advise, either, so
> I wrote some (which I hope is correct):
> The macro CCL:ADVISE lets you modify the behavior of a function or
> method in an arbitrary way.  You should not use ADVISE in production
> code, but it's useful for debugging and other tools.
> The argument list is::
> (function form &key when name define-if-not dynamic-extent-arglist)
> It basically means: whenever FUNCTION is called, run FORM.
> function
> The name of a function, or (:method name-of-method).  This is not 
> evaluated.  The advice is placed on this.  You can use (setf xxx) as a 
> function name.  FUNCTION cannot be the name of a macro or special form.
> form
> The Lisp form to be evaluated when FUNCTION is called.
> when
> (Evaluated.) One of :before, :after, or :around.  The default is 
> :before.  If :before, then evaluate FORM before calling the function. If 
> :after, evaluate FORM after calling the function. If :around, then just 
> evaluate FORM whenever the function is called; if FORM wants to do the 
> function call that would ordinarily have happened, it should evaluate 
> "(:do-it)".
> name
> (Evaluated.) A symbol that can be used to identify this piece of 
> advice, as an argument to other functions.
> define-if-not
> (NOT evaluated.) If FUNCTION is not defined, define it as a function 
> that does nothing.
> dynamic-extent-arglist
> (NOT evaluated.) If true, declare the argument list of the advised 
> function with dynamic-extent.
> The macro CCL:UNADVISE removes advice from a function.  The argument 
> list is::
> (function &key when name)
> These arguments have the same meaning as in ADVISE, except that if 
> FUNCTION is T, UNADVISE removes all advice on all functions.  Otherwise, 
> it removes all advice on FUNCTION.  If WHEN is specified, only return 
> advice for which that value of WHEN was given; NAME is analogous.
> Examples::
> (ccl:advise foo (print "about to call FOO"))
> (ccl:advise current-height (+ 5 (:do-it)) :when :around)
> Tim Bradshaw wrote:
>> I just discovered ADVISE & friends, which I failed to find any  
>> documentation for - am I not looking in the right place or is there  
>> none (I tried manual & wiki)?  If there isn't any, does anyone have  
>> any non-trivial examples of using it so I can avoid poring over the  
>> source too much.
>> [Note this is not a complaint about lack of documentation: given I'm  
>> neither paying nor contributing I'm very happy with anything I get.]
>> --tim
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