Probably   arglist in the Allegro specific package.
AFAIK MKANT's metering tool had a function for allegro for that purpose

Karsten

>>Can anyone tell me if there is a function in Allegro CL which finds the arity 
(= number of arguments) of a function or closure? Preferably also returning the 
number of optional arguments following the obligatory ones, and which arguments 
are keywords and must therefore be followed by corresponding values?>>