Generic Function Lambda Lists

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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)} [init-form [supplied-p-parameter]])}* [&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.