From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Constantin Kulikov <zxnotdead@gmail.com>
Cc: emacs-devel <emacs-devel@gnu.org>
Subject: Re: Lambda in macrolet becomes a closure? (another breaking change in emacs:))
Date: Fri, 23 Sep 2016 15:03:39 -0400 [thread overview]
Message-ID: <jwvr38acumz.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <CAFkz2yqCHpdjr7u9f3Bov1smzFoqOrMhBnHHCC=dK=c1aM7_jg@mail.gmail.com> (Constantin Kulikov's message of "Fri, 23 Sep 2016 20:19:36 +0300")
> and it seems to work well, but
>
> (setq lexical-binding nil)
> (let* ((fu #'(lambda (a) (+ a 1)))
> ba)
> (message "%s" `,fu)
> (let (byte-compile-warnings)
> (setq ba (byte-compile `(lambda (b) (funcall (quote ,fu) b)))))
> (funcall ba 2))
>
> results in a *Compile-Log* buffer pop up with
>
> Warning: (lambda (a) ...) quoted with ' rather than with #'
Notice it says "warning", not "error".
> So (if I understend correctly) I can not predict that the value of the `fu'
> will be a (closure ...) or a (lambda ...),
Or any other object that can be passed to `funcall`, indeed.
> then how I can decide how to quote this value or silence the warning?
If you're worried about the warning, silence it with
`with-no-warnings`, since in this particular case you know that the
(lambda ()...) is a function *value* and not a function expression,
hence the warning is incorrect.
We could *fix* the warning once and for all by changing the
implementation of the `function` special form so that it just always
returns a (closure ...), so that (lambda ...) is only ever used as
a source code expression and never as a function value. I think it
would be a good change, but I expect lots of people would complain about
such a gratuitous change.
Stefan
next prev parent reply other threads:[~2016-09-23 19:03 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-19 16:43 Lambda in macrolet becomes a closure? (another breaking change in emacs:)) Constantin Kulikov
2016-09-19 18:12 ` Stefan Monnier
2016-09-23 16:01 ` Michael Heerdegen
2016-09-23 16:13 ` Stefan Monnier
2016-09-23 17:19 ` Constantin Kulikov
2016-09-23 19:03 ` Stefan Monnier [this message]
2016-09-25 11:06 ` Constantin Kulikov
2016-09-25 14:15 ` Stefan Monnier
2016-09-25 18:01 ` Michael Heerdegen
2016-09-25 18:53 ` Stefan Monnier
2016-09-27 9:13 ` Constantin Kulikov
2016-09-27 9:19 ` Constantin Kulikov
2016-09-27 11:53 ` Constantin Kulikov
2016-09-27 14:57 ` Michael Heerdegen
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