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| ANSI Common Lisp 3 Evaluation and Compilation 3.4 Lambda Lists ### 3.4.4 Macro Lambda Lists A macro lambda list is used in describing macros defined by the operators in the next figure.
Operators that use Macro Lambda Lists
define-compiler-macro | defmacro | macrolet
define-setf-expander |  |
With the additional restriction that an environment parameter may appear only once (at any of the positions indicated), a macro lambda list has the following syntax:
reqvars::= | `{`var | pattern`}`
optvars::= | `[``&optional` `{`var | (`{`var | pattern`}` [init-form [supplied-p-parameter ] ])`}`*`]`
restvar::= | `[``{``&rest` | `&body``}` `]``{`var | pattern`}`
keyvars::= | [`&key` `{`var | (`{`var | (keyword-name`{`var | pattern`}` )`}` [init-form [supplied-p-parameter ] ])`}`*
| [`&allow-other-keys`]]
auxvars::= | `[``&aux` `{`var | (var [init-form ] )`}`*`]`
envvar::= | `[``&environment` var`]`
wholevar::= | `[``&whole` var`]`
lambda-list::= | (wholevar envvar reqvars envvar optvars envvar
| restvar envvar keyvars envvar auxvars envvar) |
| (wholevar envvar reqvars envvar optvars envvar `.` var)
pattern::= | (wholevarreqvarsoptvarsrestvarkeyvarsauxvars) |
| (wholevar reqvars optvars `.` var)

A macro lambda list can contain the lambda list keywords shown in the next figure.
Lambda List Keywords used by Macro Lambda Lists
&allow-other-keys | &environment | &rest
&aux | &key | &whole
&body | &optional |
Optional parameters (introduced by &optional) and keyword parameters (introduced by &key) can be supplied in a macro lambda list, just as in an ordinary lambda list. Both may contain default initialization forms and supplied-p parameters. &body is identical in function to &rest, but it can be used to inform certain output-formatting and editing functions that the remainder of the form is treated as a body, and should be indented accordingly. Only one of &body or &rest can be used at any particular level; see Section 3.4.4.1 Destructuring by Lambda Lists. &body can appear at any level of a macro lambda list; for details, see Section 3.4.4.1 Destructuring by Lambda Lists. &whole is followed by a single variable that is bound to the entire macro-call form; this is the value that the macro function receives as its first argument. If &whole and a following variable appear, they must appear first in lambda-list, before any other parameter or lambda list keyword. &whole can appear at any level of a macro lambda list. At inner levels, the &whole variable is bound to the corresponding part of the argument, as with &rest, but unlike &rest, other arguments are also allowed. The use of &whole does not affect the pattern of arguments specified. &environment is followed by a single variable that is bound to an environment representing the lexical environment in which the macro call is to be interpreted. This environment should be used with macro-function, get-setf-expansion, compiler-macro-function, and macroexpand (for example) in computing the expansion of the macro, to ensure that any lexical bindings or definitions established in the compilation environment are taken into account. &environment can only appear at the top level of a macro lambda list, and can only appear once, but can appear anywhere in that list; the &environment parameter is bound along with &whole before any other variables in the lambda list, regardless of where &environment appears in the lambda list. The object that is bound to the environment parameter has dynamic extent. Destructuring allows a macro lambda list to express the structure of a macro call syntax. If no lambda list keywords appear, then the macro lambda list is a tree containing parameter names at the leaves. The pattern and the macro form must have compatible tree structure; that is, their tree structure must be equivalent, or it must differ only in that some leaves of the pattern match non-atomic objects of the macro form. For information about error detection in this situation, see Section 3.5.1.7 Destructuring Mismatch. A destructuring lambda list (whether at top level or embedded) can be dotted, ending in a parameter name. This situation is treated exactly as if the parameter name that ends the list had appeared preceded by &rest. It is permissible for a macro form (or a subexpression of a macro form) to be a dotted list only when `(... &rest var)` or `(... . var)` is used to match it. It is the responsibility of the macro to recognize and deal with such situations. 3.4.4.1 Destructuring by Lambda Lists

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