3.4.2 Generic Function Lambda Lists

A generic function lambda list is used to describe the overall shape of the argument list to be accepted by a generic function. Individual method signatures might contribute additional keyword parameters to the lambda list of the effective method.

A generic function lambda list is used by defgeneric.

A generic function lambda list has the following syntax:

lambda-list::= (var* 
                [&optional {var | (var)}*] 
                [&rest var] 
                [&key {var | ({var | (keyword-name var)})}* [&allow-other-keys]]) 

A generic function lambda list can contain the lambda list keywords shown in the next figure.

&allow-other-keys  &optional    
&key               &rest        

Figure 3-14. Lambda List Keywords used by Generic Function Lambda Lists

A generic function lambda list differs from an ordinary lambda list in the following ways:

Required arguments

Zero or more required parameters must be specified.

Optional and keyword arguments

Optional parameters and keyword parameters may not have default initial value forms nor use supplied-p parameters.

Use of &aux

The use of &aux is not allowed.