From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Andrea Corallo <akrl@sdf.org>
Cc: Zhu Zihao <all_but_last@163.com>, Tomas Hlavaty <tom@logand.com>,
emacs-devel@gnu.org
Subject: Re: named-let
Date: Mon, 11 Jan 2021 18:57:36 -0500 [thread overview]
Message-ID: <jwvo8hv3ue7.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <xjfr1mrdpfb.fsf@sdf.org> (Andrea Corallo's message of "Mon, 11 Jan 2021 23:28:08 +0000")
>> [ TCO has also undesirable interactions with debugging/tracing, but
>> I think that would be a secondary concern which should be
>> manageable somehow. ]
>
> It's also a change in semantic as one must assume that `bar' is not
> redefining `foo'.
>
> (defun foo ()
> (bar)
> (foo))
I think there's a bit of confusion: you can have TCO without having to
pay any attention to whether `bar` changes `foo`. True TCO will also
avoid eating up stack space when you have code like
(defun foo (x)
(baz (1+ x)))
or
(defun foo (x)
(funcall (if (something) #'bar #'foo) (1+ x)))
or
(defun foo (x)
(let ((k (lambda (y) (foo (1+ x)))))
(k 5)))
or ... and that doesn't depend on analyzing the code at all.
IOW, it shouldn't matter whether it's a recursive call or whether it's
a call to "self": all calls in tail position would conceptually pop
their stack frame before jumping to the destination function.
Stefan
next prev parent reply other threads:[~2021-01-11 23:57 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-09 1:43 named-let Stefan Monnier
2021-01-09 8:58 ` named-let tomas
2021-01-09 16:01 ` named-let Joost Kremers
2021-01-09 21:48 ` named-let Stefan Monnier
2021-01-09 15:23 ` named-let Tomas Hlavaty
2021-01-09 16:44 ` named-let Stefan Monnier
2021-01-09 17:03 ` named-let Helmut Eller
2021-01-09 18:43 ` named-let Stefan Monnier
2021-01-09 18:47 ` named-let Tomas Hlavaty
2021-01-10 18:49 ` named-let Zhu Zihao
2021-01-11 22:27 ` named-let Tomas Hlavaty
2021-01-11 22:36 ` named-let Stefan Monnier
2021-01-11 22:48 ` named-let Tomas Hlavaty
2021-01-11 22:50 ` named-let Andrea Corallo via Emacs development discussions.
2021-01-11 23:10 ` named-let Stefan Monnier
2021-01-11 23:28 ` named-let Andrea Corallo via Emacs development discussions.
2021-01-11 23:57 ` Stefan Monnier [this message]
2021-01-12 9:24 ` named-let Andrea Corallo via Emacs development discussions.
2021-01-12 18:07 ` named-let Stefan Monnier
2021-01-12 18:50 ` named-let Andrea Corallo via Emacs development discussions.
2021-01-12 9:13 ` named-let Helmut Eller
2021-01-13 8:11 ` named-let Zhu Zihao
2021-01-13 14:01 ` named-let Stefan Monnier
2021-01-11 22:40 ` named-let Andrea Corallo via Emacs development discussions.
2021-01-11 22:51 ` named-let Tomas Hlavaty
2021-01-11 23:04 ` named-let Andrea Corallo via Emacs development discussions.
2021-01-12 0:12 ` named-let Tomas Hlavaty
2021-01-20 19:44 ` named-let Stefan Monnier
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