Path: csiph.com!usenet.pasdenom.info!news.redatomik.org!newsfeed.xs4all.nl!newsfeed8.news.xs4all.nl!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path: <ian.g.kelly@gmail.com>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.023
X-Spam-Evidence: '*H*': 0.95; '*S*': 0.00; 'omit': 0.07; 'compiler.': 0.09; 'bug': 0.10; 'python': 0.10; 'explicitly': 0.15; 'result.': 0.15; 'confusion': 0.16; 'entirely.': 0.16; 'foo()': 0.16; 'programmer,': 0.16; 'wrote:': 0.16; 'pointed': 0.18; "shouldn't": 0.18; 'programmer': 0.18; '>>>': 0.20; '2015': 0.20; 'controlling': 0.22; 'explicit': 0.22; 'am,': 0.23; 'header:In- Reply-To:1': 0.24; 'mon,': 0.24; "doesn't": 0.26; 'chris': 0.26; 'message-id:@mail.gmail.com': 0.27; '14,': 0.27; '13,': 0.29; 'tail': 0.29; "they'll": 0.29; 'subject:/': 0.30; 'statement': 0.32; 'point': 0.33; 'controls': 0.33; 'changing': 0.34; 'definition': 0.34; 'tue,': 0.34; 'received:google.com': 0.35; 'could': 0.35; 'instead': 0.36; 'keyword': 0.36; 'to:addr:python- list': 0.36; 'pm,': 0.36; 'subject:: ': 0.37; 'responsible': 0.37; "won't": 0.38; 'mean': 0.38; 'means': 0.39; 'why': 0.39; 'to:addr:python.org': 0.40; 'forget': 0.60; 'behavior': 0.61; 'today.': 0.67; 'jul': 0.72; 'led': 0.72; 'miss': 0.77; 'viewed': 0.79; 'difference.': 0.84; 'to:name:python': 0.84; 'mistakenly': 0.91
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type; bh=95hByLWtZ+Mya3d/0LqBydvdx1PxKqfErL8nOrsZjkg=; b=W5rYxVmeqvVdw4w+3V3UtuW+MTfZ9UJ0hpfIsH1uFAP8k3CnWW6pilV6nCGEOjWx8w icFv8w8W5X5R6fzx3jD68U0oofoSjmJi6TGFIRxRSkUtNoIEK1Tlg68cYUExkqnp7iIt ovlTt0BlqN2seZuVANM64fEwxlj0ZglNTgFMd4pAKJhvzKjqUKraZNgqEUxBTThqp3ja j4C0xfEPEq742qQBg9fMDQX+ManpCR0veeDdElJ2tz6CtjCbD8THt/LsYrft9MQ22rpd Dqdmom7aIChDr245+5WFbnWJrnw2BkI4HmBIV5dXW9PXKup+pWdDJIbxaKWHZ8cliraG hCcA==
X-Received: by 10.13.251.199 with SMTP id l190mr45324027ywf.148.1436879758584; Tue, 14 Jul 2015 06:15:58 -0700 (PDT)
MIME-Version: 1.0
In-Reply-To: <87pp3vm93f.fsf@elektro.pacujo.net>
References: <CAD+URuj-4e62-9hvpiLsrBP1M6kXRyZhZ6XyL01gWWnDoShvNg@mail.gmail.com> <CAPTjJmrnd2cdA75ROZUKsJfYMdYUXkxRbEN50UE_-r0Jg=c5nQ@mail.gmail.com> <55A3A853.4040006@rece.vub.ac.be> <CAPTjJmr92j+2DDPsZxynoHyZTTCpc-48cWCVrx_fT3dA0j_Osg@mail.gmail.com> <55A3C366.6060602@rece.vub.ac.be> <mailman.468.1436796350.3674.python-list@python.org> <87fv4r1fre.fsf@jester.gateway.sonic.net> <CAPTjJmqjuh2_s7-GzfqMNnpimS61W9m3KE5V9yd0TXm9VhTc7A@mail.gmail.com> <mailman.483.1436852831.3674.python-list@python.org> <877fq3nuwo.fsf@elektro.pacujo.net> <mailman.493.1436861666.3674.python-list@python.org> <87pp3vm93f.fsf@elektro.pacujo.net>
From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Tue, 14 Jul 2015 07:15:19 -0600
Subject: Re: Possibly Pythonic Tail Call Optimization (TCO/TRE)
To: Python <python-list@python.org>
Content-Type: text/plain; charset=UTF-8
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.20+
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.504.1436879766.3674.python-list@python.org>
Lines: 38
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1436879766 news.xs4all.nl 2878 [2001:888:2000:d::a6]:45629
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:93808

On Tue, Jul 14, 2015 at 2:33 AM, Marko Rauhamaa <marko@pacujo.net> wrote:
> Ian Kelly <ian.g.kelly@gmail.com>:
>
>> On Mon, Jul 13, 2015 at 11:57 PM, Marko Rauhamaa <marko@pacujo.net> wrote:
>>> How about "return"?
>>
>> I think you miss my point entirely. "return" doesn't mean tail-call
>> optimize;
>
> Why not?
>
>> it just means to return the result.
>
> Same difference.
>
>> This is what led to the confusion responsible for the bug that Chris
>> pointed out in the first place. With a keyword that explicitly means
>> "perform tail-call optimization *and* return",
>
> That could well be the explicit definition of the "return" statement in
> Python without changing the behavior of any working Python program
> today.

To the compiler. It won't be viewed that way be the programmer,
however. So they'll forget that the "return" is necessary to the
optimization and just write quicksort() instead of return quicksort().

>> the association of the keyword with the optimization is much clearer,
>> and the programmer is much less likely to mistakenly omit it.
>
> The programmer shouldn't be controlling tail call optimizations.

The programmer controls it regardless.

    return foo()  # TCO

    result = foo()  # No TCO
    return result  # No TCO