#### 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)})}* pt [`&allow-other-keys`]`]`)

A generic function lambda list can contain the lambda list keywords shown in Figure 3–14.

      &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.