Major Section: MISCELLANEOUS
Examples: (x y z) (x y z &optional max (base '10 basep)) (x y &rest rst) (x y &key max base) (&whole sexpr x y)
The ``lambda-list'' of a macro definition may include simple formal
parameter names as well as appropriate uses of the following
lambda-list keywords from CLTL (pp. 60 and 145), respecting the
order shown:
&whole, &optional, &rest, &body, &key, and &allow-other-keys.ACL2 does not support
&aux and &environment. In addition, we make
the following restrictions:
(1) initialization forms in
&optionaland&keyspecifiers must be quoted values;(2)
&allow-other-keysmay only be used once, as the last specifier; and(3) destructuring is not allowed.
You are encouraged to experiment with the macro facility. One way to do so is to define a macro that does nothing but return the quotation of its arguments, e.g.,
(defmacro demo (x y &optional opt &key key1 key2) (list 'quote (list x y opt key1 key2)))You may then execute the macro on some sample forms, e.g.,
term value
(demo 1 2) (1 2 NIL NIL NIL)
(demo 1 2 3) (1 2 3 NIL NIL)
(demo 1 2 :key1 3) error: non-even key/value arglist
(because :key1 is used as opt)
(demo 1 2 3 :key2 5) (1 2 3 NIL 5)
In particular, Common Lisp specifies that if you use both &rest and
&key, then both will be bound using the same list of arguments. The
following example should serve to illustrate how this works.
ACL2 !>(defmacro foo (&rest args &key k1 k2 k3)
(list 'quote (list args k1 k2 k3)))
Summary
Form: ( DEFMACRO FOO ...)
Rules: NIL
Warnings: None
Time: 0.00 seconds (prove: 0.00, print: 0.00, other: 0.00)
FOO
ACL2 !>(foo :k1 3 :k2 4 :k3 5)
((:K1 3 :K2 4 :K3 5) 3 4 5)
ACL2 !>(foo :k1 3 :k2 4)
((:K1 3 :K2 4) 3 4 NIL)
ACL2 !>(foo :k1 3 :bad-key 7)
ACL2 Error in macro expansion: Illegal key/value args (:BAD-KEY 7)
in macro expansion of (FOO :K1 3 :BAD-KEY 7). The argument list for
FOO is
(&REST ARGS &KEY K1 K2 K3).
ACL2 !>
If we don't want to get the error above, we can use
&allow-other-keys, as follows.
ACL2 !>(defmacro bar (&rest args &key k1 k2 k3
&allow-other-keys)
(list 'quote (list args k1 k2 k3)))
Summary
Form: ( DEFMACRO BAR ...)
Rules: NIL
Time: 0.00 seconds (prove: 0.00, print: 0.00, other: 0.00)
BAR
ACL2 !>(bar :k1 3 :bad-key 7)
((:K1 3 :BAD-KEY 7) 3 NIL NIL)
ACL2 !>
Also see trans.