From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Michael Heerdegen <michael_heerdegen@web.de>
Cc: emacs-devel@gnu.org
Subject: Re: Why is FUNC in cl-callf not allowed to be an expression?
Date: Sat, 18 May 2019 10:09:41 -0400 [thread overview]
Message-ID: <jwvlfz3q3ao.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <87tvdshew9.fsf@web.de> (Michael Heerdegen's message of "Sat, 18 May 2019 00:53:10 +0200")
> (defmacro gv-place-bind (bindings &rest body)
Hmm... "bind", eh? I don't think that's different enough.
How 'bout something more like a "gv-alias"?
> Writing the docstring made me thoughtful though - how is this different
> from symbol-macrolet?
Indeed, they're closely related but symbol-macrolet does not "evaluates"
anything at the "binding" site. Also it can also be used for purposes
different from "places", e.g. to keep a log of all the accessed to
a "variable" (tho, we could just as well create a (journaled PLACE)
pseudo place which would record accesses in the very same way).
Yeah, maybe a "place alias" is a generalization of symbol-macro.
Actually, no: symbol-macro can also expand to other macro-calls which
are supposed to be re-expanded at each use-site, AFAIK, so it can
macro-expand to something different every time the "variable" is
referenced, which is not the case of places, I think.
Maybe people over on comp.lang.lisp (or other Lisp discussion area)
would have some insight about this.
> My second point in this message: thinking once more about callf, we
> could also support a syntax like (callf (with EXPR) PLACE ARG) or
> something like that to support expressions as first arg.
You can already do that, except that `with` is spelled `lambda (it)`:
(cl-callf (lambda (it) EXPR) PLACE)
Notice that the gv-callf we discussed are equivalent to the above rather
than to something where the EXPR is evaluated to decide which function
to call. To me, the benefit of
(gv-modify it PLACE EXPR)
[with or without the `it`] is that expressions appear in the order in
which they're evaluated, and also that it looks more like `setf`, which
is right since this is about doing a `setf` just with the added twist
that it can refer to the old value of the variable to compute the
new one.
Stefan
next prev parent reply other threads:[~2019-05-18 14:09 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-09 21:52 Why is FUNC in cl-callf not allowed to be an expression? Michael Heerdegen
2019-05-10 0:47 ` Stefan Monnier
2019-05-10 11:32 ` Michael Heerdegen
2019-05-10 13:28 ` Stefan Monnier
2019-05-10 14:19 ` Stefan Monnier
2019-05-10 14:22 ` Stefan Monnier
2019-05-10 15:18 ` Michael Heerdegen
2019-05-13 16:47 ` Stefan Monnier
2019-05-14 12:36 ` Michael Heerdegen
2019-05-14 23:32 ` Michael Heerdegen
2019-05-15 2:02 ` Stefan Monnier
2019-05-15 16:38 ` Michael Heerdegen
2019-05-15 17:19 ` Michael Heerdegen
2019-05-16 2:18 ` Michael Heerdegen
2019-05-16 13:12 ` Stefan Monnier
2019-05-16 14:37 ` Michael Heerdegen
2019-05-16 15:09 ` Michael Heerdegen
2019-05-16 19:34 ` Stefan Monnier
2019-05-16 21:46 ` Michael Heerdegen
2019-05-16 23:06 ` Stefan Monnier
2019-05-17 22:53 ` Michael Heerdegen
2019-05-18 14:09 ` Stefan Monnier [this message]
2019-05-20 23:25 ` Michael Heerdegen
2019-05-21 2:01 ` Stefan Monnier
2019-05-21 2:47 ` Michael Heerdegen
2019-05-21 10:16 ` Noam Postavsky
2019-05-21 16:38 ` Michael Heerdegen
2019-05-21 17:38 ` Stefan Monnier
2019-05-21 7:26 ` Andy Moreton
2019-05-23 23:02 ` Michael Heerdegen
2019-05-22 1:00 ` Michael Heerdegen
2019-05-23 1:50 ` Michael Heerdegen
2019-05-23 3:38 ` Stefan Monnier
2019-05-23 23:38 ` Michael Heerdegen
2019-05-24 15:29 ` Stefan Monnier
2019-05-28 19:54 ` Michael Heerdegen
2019-05-27 0:20 ` Michael Heerdegen
2019-05-29 17:02 ` Stefan Monnier
2019-05-15 19:17 ` Michael Heerdegen
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