Re: Uniform Function Call Syntax (UFCS)

X-Received	by 10.66.189.234 with SMTP id gl10mr274238pac.20.1402259750779; Sun, 08 Jun 2014 13:35:50 -0700 (PDT)
X-Received	by 10.140.95.141 with SMTP id i13mr326055qge.3.1402259750716; Sun, 08 Jun 2014 13:35:50 -0700 (PDT)
Path	csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!news.glorb.com!h3no188966igd.0!news-out.google.com!q9ni356qaj.0!nntp.google.com!j5no2561739qaq.1!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail
Newsgroups	comp.lang.python
Date	Sun, 8 Jun 2014 13:35:50 -0700 (PDT)
In-Reply-To	<mailman.10890.1402249956.18130.python-list@python.org>
Complaints-To	groups-abuse@google.com
Injection-Info	glegroupsg2000goo.googlegroups.com; posting-host=95.149.162.93; posting-account=KsoyMQkAAAAewqMJYXCNG9IZduQXE-lZ
NNTP-Posting-Host	95.149.162.93
References	<8b96ae27-20fa-4df9-807e-c806fed983c0@googlegroups.com> <mailman.10859.1402169265.18130.python-list@python.org> <bvhsgeF2on9U2@mid.individual.net> <1dd863ba-09e5-439b-8669-db65f3e999eb@googlegroups.com> <roy-68FCA5.10591408062014@news.panix.com> <927afb61-be0e-43a1-8aab-107e77a013fc@googlegroups.com> <CAPTjJmpGwu5xiH3kAYHO5Lk8Ycib44an-wkAVwSLPF67uWC=sg@mail.gmail.com> <CALwzid=vaj1Hj_OTVMYCwXub4=bQEqrV=hC+YYmCXctvAqXtsw@mail.gmail.com> <CAPTjJmrD28nS=tj_bm_SkwuqLNSY4F_RAKpKAWTYNh9x6RtBCQ@mail.gmail.com> <mailman.10890.1402249956.18130.python-list@python.org>
User-Agent	G2/1.0
MIME-Version	1.0
Message-ID	<23f69b68-6efb-49b7-bd01-ada3dea027d3@googlegroups.com> (permalink)
Subject	Re: Uniform Function Call Syntax (UFCS)
From	jongiddy <jongiddy@gmail.com>
Injection-Date	Sun, 08 Jun 2014 20:35:50 +0000
Content-Type	text/plain; charset=ISO-8859-1
Content-Transfer-Encoding	quoted-printable
Xref	csiph.com comp.lang.python:72993

Show key headers only | View raw

On Sunday, 8 June 2014 18:24:28 UTC+1, Ian  wrote:
> 
> But that would all be done in getattr, so I don't think it affects
> hasattr's implementation at all.  Since hasattr doesn't push anything
> onto the stack, getattr doesn't have to care whether it was called
> directly from Python or indirectly via getattr; either way the scope
> it needs is just the top frame of the stack.
> 
> Could be a different matter in other implementations, though.

In CPython, the UFCS would not be done in PyObject_GetAttr() as that would affect hasattr() as well. Instead, it would be implemented in the bytecode for LOAD_ATTR. If LOAD_ATTR was about to return an AttributeError, e.g. for [].len, it would perform the equivalent of a LOAD_NAME operation, with the difference that if the name is not found or is not callable, it returns AttributeError instead of NameError.

If the name is found, then it would return something: for [].len, it would return the len() function wrapped to know that it's first argument was the list, which might be done by creating a fake Method object, as shown in Ian's code.

But getattr([], 'len') and hasattr([], 'len') would both return False.

I'm beginning to think it is too un-Pythonic - too much implicitness, unless it can be spelt differently, something like [].len(_) or [].len(...) to explicitly indicate that it plans to call a function, but might call a method if one is available.

Thread

Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-06 23:45 -0700
  Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-07 13:20 -0600
    Re: Uniform Function Call Syntax (UFCS) Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-06-08 13:27 +1200
      Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 01:26 -0700
        Re: Uniform Function Call Syntax (UFCS) Paul Sokolovsky <pmiscml@gmail.com> - 2014-06-08 15:06 +0300
          Re: Uniform Function Call Syntax (UFCS) Marko Rauhamaa <marko@pacujo.net> - 2014-06-08 18:56 +0300
            Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-08 10:38 -0600
            Re: Uniform Function Call Syntax (UFCS) Paul Sokolovsky <pmiscml@gmail.com> - 2014-06-08 19:40 +0300
            Re: Uniform Function Call Syntax (UFCS) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 04:33 +0000
              Re: Uniform Function Call Syntax (UFCS) Marko Rauhamaa <marko@pacujo.net> - 2014-06-09 09:25 +0300
                Re: Uniform Function Call Syntax (UFCS) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 09:09 +0000
                Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 19:13 +1000
                Re: Uniform Function Call Syntax (UFCS) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 13:37 +0000
                Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-10 01:08 +1000
          Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 09:24 -0700
            Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 09:34 -0700
            Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-08 10:54 -0600
            Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 03:10 +1000
              Re: Uniform Function Call Syntax (UFCS) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 03:20 +0000
                Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 13:44 +1000
                Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 23:38 -0700
                Re: Uniform Function Call Syntax (UFCS) Roy Smith <roy@panix.com> - 2014-06-08 23:45 -0400
      Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 02:25 -0700
        Re: Uniform Function Call Syntax (UFCS) Roy Smith <roy@panix.com> - 2014-06-08 10:59 -0400
          Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 08:39 -0700
            Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 02:48 +1000
              Re: Uniform Function Call Syntax (UFCS) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 03:53 +0000
                Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 14:53 +1000
                Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-09 08:24 -0600
                Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-09 23:43 -0700
            Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-08 11:08 -0600
            Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 03:13 +1000
            Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-08 11:24 -0600
              Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 13:35 -0700
    Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 01:15 -0700
      Re: Uniform Function Call Syntax (UFCS) Paul Sokolovsky <pmiscml@gmail.com> - 2014-06-08 14:52 +0300
      Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-08 11:00 -0600

csiph-web