Comments (3)
Good first question! The reason is that list
evaluates the arguments 'setq
then x
and (list '+ x 1))
. But this x
is the problem, because x
is first replaced by n
then the n
is evaluated by list
. A macro constructs code, but the code is still evaluated in a way that may not be immediately intuitive. This is one of the reasons why Lisp implementations have so-called quasiquotes to make this possible, but not easy (ugly) to look at IMHO. Maybe we should add quasiquotes?
EDIT: It's a different problem, it looks like something is not working in setq
:
>(define n 1)
>(setq n (+ n 1))
ERR 3 unbound symbol
There is a typo in f_setq
that uses 1
instead of *e
(environment).
from lisp.
However ...
This macro works in other lisp 1's. E.g. in tiny-lisp the following is okay:
(setq ++ (macro (x) (list 'setq x (list '+ x 1))))
(setq r 4) (++ r)
Now r equals 5. Quasiquotes not needed, although it would be nice to have them.
from lisp.
Should work now after the setq
typo fix, see my EDIT.
from lisp.
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from lisp.