Re: find-method

[bill@cambridge.apple.com (Bill St. Clair)]

>3. What I really want to find out is: given an instance and the symbol name of a method,
>   Is (meth-name inst) going to error due to the lack of meth-name existing?
>   Is find-method the correct fn to be calling?

As Kim Barrett said, COMPUTE-APPLICABLE-METHODS will do what you want.

If you don't care about portability, and would like to be faster and cons
less than COMPUTE-APPLICABLE-METHODS,  MCL has a function that is probably
exactly what you want:

method-exists-p generic-function &rest args

looks for a primary method specialized on the given generic function
which is applicable to the given args. If found, returns the method,
otherwise, returns NIL. If generic-function is not a generic function
or the name of a generic function, returns NIL. If there are fewer
args than there are required arguments to generic-function, ignores
the unspecified specializers (see the last example). Does not cons.

Example:

? (defmethod brack ((x number)) x)
#<STANDARD-METHOD BRACK (NUMBER)>
? (method-exists-p 'brack 1)
#<STANDARD-METHOD BRACK (NUMBER)>
? (method-exists-p 'brack nil)
NIL
? (method-exists-p 'defun 'brack)
NIL
? (defmethod bretch ((x number) (y list)) (cons x y))
#<STANDARD-METHOD BRETCH (NUMBER LIST)>
? (method-exists-p 'bretch 1 nil)
#<STANDARD-METHOD BRETCH (NUMBER LIST)>
? (method-exists-p 'bretch 1 'foo)
NIL
? (method-exists-p 'bretch 1)
#<STANDARD-METHOD BRETCH (NUMBER LIST)>
?