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Re: allow line break at operators

References (15 earlier) <slrnj4am5d.1es6.usenet-nospam@guild.seebs.net> <92b8f192-d7fc-4c60-87ad-71b12652f3a2@k8g2000yqk.googlegroups.com> <mailman.2233.1313179799.1164.python-list@python.org> <roy-D85560.09413315082011@news.panix.com> <4e492d08$0$30003$c3e8da3$5496439d@news.astraweb.com>
Date 2011-08-15 15:42 +0100
Subject Re: allow line break at operators
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.11.1313419331.27778.python-list@python.org> (permalink)

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On Mon, Aug 15, 2011 at 3:28 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> And of course, once you start using floating point numbers, you can't assume
> commutativity:
>
>>>> 0.1 + 0.7 + 0.3 == 0.3 + 0.7 + 0.1
> False
>

This isn't because programming languages fail to follow mathematics;
it's because floating point numbers do not represent real numbers.
Python doesn't support substring removal using the subtraction
operator, but I'd have to say that floats more closely parallel
strings and other high level objects than they do mathematical reals.
If Python treated __sub__(str,str) as str.replace(str,"") then:


>>> "hello world" + "asdfqwer" - "d"
"hello worlasfqwer"
>>> "hello world" - "d" + "asdfqwer"
"hello worlasdfqwer"

Nobody would expect strings to behave mathematically with subtraction,
because negatives don't make sense. Even sets don't quite work,
although they're closer:

>>> set("asdf")-set("test")
{'a', 'd', 'f'}

There's no way, in a set, to show a negative reference to 't' and 'e'.
In theory you could do this with dictionaries or collections.Counter,
but subtracting a Counter from a Counter doesn't produce negative
numbers either. No, these constructs do not subtract algebraically,
and I do not think it would be any improvement to the language if they
did.

ChrisA

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Re: allow line break at operators Yingjie Lan <lanyjie@yahoo.com> - 2011-08-09 23:05 -0700
  Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-10 18:32 +1000
    Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-10 09:39 +0100
    Re: allow line break at operators Dan Sommers <dan@tombstonezero.net> - 2011-08-10 09:56 +0000
      Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-11 00:44 +1000
    Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-10 11:26 +0100
      Re: allow line break at operators Duncan Booth <duncan.booth@invalid.invalid> - 2011-08-10 12:25 +0000
        Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-10 13:42 +0100
        Re: allow line break at operators Yingjie Lan <lanyjie@yahoo.com> - 2011-08-10 05:58 -0700
        Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-10 15:45 +0100
        Re: allow line break at operators Yingjie Lan <lanyjie@yahoo.com> - 2011-08-10 06:19 -0700
        Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-10 16:56 +0100
          Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-10 17:55 +0000
            Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-11 07:51 +1000
              Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-10 23:42 +0100
                Re: allow line break at operators Neil Cerutti <neilc@norwich.edu> - 2011-08-11 14:40 +0000
              Re: Python & Sullivan Tim Chase <python.list@tim.thechases.com> - 2011-08-10 18:26 -0500
                Re: Python & Sullivan Ben Finney <ben+python@benfinney.id.au> - 2011-08-11 10:57 +1000
              Re: Python & Sullivan Chris Angelico <rosuav@gmail.com> - 2011-08-11 00:54 +0100
              Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-11 04:59 +0000
                Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-11 15:56 +1000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-11 21:19 +0000
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-12 00:58 +0100
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-12 11:40 +1000
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-12 08:09 +0100
                Re: allow line break at operators Neil Cerutti <neilc@norwich.edu> - 2011-08-12 12:57 +0000
                Re: allow line break at operators Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2011-08-12 14:54 +0200
                Re: allow line break at operators Tim Roberts <timr@probo.com> - 2011-08-14 22:22 -0700
                Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-12 18:59 +1000
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-12 20:40 +1000
                Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-12 21:16 +1000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-12 16:33 +0000
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-11 22:29 +1000
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-11 22:40 +1000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-11 21:19 +0000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-11 21:19 +0000
                Re: allow line break at operators Ethan Furman <ethan@stoneleaf.us> - 2011-08-11 15:43 -0700
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-12 06:34 +0000
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-12 08:20 +0100
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-12 08:33 -0700
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-12 20:52 +0100
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-12 16:33 +0000
                Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-12 20:39 +1000
                Re: allow line break at operators Chris Rebert <clp2@rebertia.com> - 2011-08-12 10:03 -0700
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-12 18:37 +0000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-12 16:33 +0000
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-12 21:01 +0100
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-12 21:06 +0000
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-12 08:26 -0700
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-12 16:33 +0000
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-12 10:57 -0700
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-12 21:09 +0100
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-12 21:06 +0000
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-13 08:39 +1000
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-12 23:50 +0100
                Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-13 09:19 +1000
                Re: allow line break at operators Tim Chase <python.list@tim.thechases.com> - 2011-08-12 18:53 -0500
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-13 00:39 +0000
                Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-13 10:57 +1000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-13 02:34 +0000
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-13 18:50 -0700
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-13 19:07 -0700
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-13 18:59 -0700
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-14 17:10 +1000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-14 08:07 +0000
                Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-14 19:25 +1000
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-15 00:26 +1000
                Re: allow line break at operators Roy Smith <roy@panix.com> - 2011-08-14 11:35 -0400
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-15 03:24 +1000
                Re: Re: allow line break at operators Dave Angel <davea@ieee.org> - 2011-08-14 17:46 -0400
                Re: allow line break at operators Roy Smith <roy@panix.com> - 2011-08-14 18:46 -0400
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-15 00:02 +0100
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-14 16:39 +0100
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-15 03:26 +1000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-14 19:01 +0000
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-15 11:54 +1000
                Re: allow line break at operators Chris Rebert <clp2@rebertia.com> - 2011-08-14 19:10 -0700
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-15 04:28 +0000
                Re: allow line break at operators Tim Chase <python.list@tim.thechases.com> - 2011-08-15 06:40 -0500
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-15 23:30 +1000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-15 16:32 +0000
                Re: allow line break at operators alex23 <wuwei23@gmail.com> - 2011-08-15 21:13 -0700
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-15 21:37 -0700
                Re: allow line break at operators alex23 <wuwei23@gmail.com> - 2011-08-15 23:49 -0700
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-16 11:56 -0700
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-15 04:28 +0000
                Re: allow line break at operators Terry Reedy <tjreedy@udel.edu> - 2011-08-15 03:31 -0400
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-15 14:21 -0700
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-15 09:27 +0100
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-14 09:34 +0100
                Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-14 19:27 +1000
                Re: allow line break at operators Ethan Furman <ethan@stoneleaf.us> - 2011-08-14 03:51 -0700
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-14 12:59 +0100
                Re: allow line break at operators Teemu Likonen <tlikonen@iki.fi> - 2011-08-14 12:46 +0300
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-14 19:01 +0000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-14 19:01 +0000
                Re: allow line break at operators Chris Rebert <clp2@rebertia.com> - 2011-08-14 01:44 -0700
                Re: allow line break at operators Teemu Likonen <tlikonen@iki.fi> - 2011-08-16 07:04 +0300
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-13 19:18 -0700
                Re: allow line break at operators Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-08-13 13:19 +1200
                Re: allow line break at operators Johann Hibschman <jhibschman+usenet@gmail.com> - 2011-08-15 08:27 -0500
                Re: allow line break at operators Roy Smith <roy@panix.com> - 2011-08-15 09:41 -0400
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-15 15:16 +0100
                Re: allow line break at operators Roy Smith <roy@panix.com> - 2011-08-15 20:34 -0400
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-16 01:37 +0100
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-16 00:28 +1000
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-15 15:42 +0100
                Re: allow line break at operators Roy Smith <roy@panix.com> - 2011-08-15 20:30 -0400
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-16 00:39 +0000
                Re: allow line break at operators Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-08-16 12:43 +1200
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-15 16:32 +0000
                Re: allow line break at operators Ethan Furman <ethan@stoneleaf.us> - 2011-08-12 13:35 -0700
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-12 21:06 +0000
                Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-13 08:03 +1000
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-12 22:14 +0000
                Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-13 08:36 +1000
                Re: allow line break at operators Terry Reedy <tjreedy@udel.edu> - 2011-08-12 20:15 -0400
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-13 00:44 +0000
                Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-08-13 18:25 -0700
                Re: allow line break at operators Ben Finney <ben+python@benfinney.id.au> - 2011-08-13 08:12 +1000
                RE: allow line break at operators "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2011-08-16 15:51 -0400
                RE: allow line break at operators "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2011-08-16 15:26 -0400
                Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-16 20:19 +0000
                Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-16 21:05 +0100
            Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-11 10:32 +1000
              Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-11 01:47 +0100
              Re: allow line break at operators Seebs <usenet-nospam@seebs.net> - 2011-08-11 04:59 +0000
        Re: allow line break at operators Yingjie Lan <lanyjie@yahoo.com> - 2011-08-10 19:52 -0700
          Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-11 14:18 +1000
            Re: allow line break at operators Chris Rebert <clp2@rebertia.com> - 2011-08-11 00:50 -0700
            Re: allow line break at operators Vito 'ZeD' De Tullio <zak.mc.kraken@libero.it> - 2011-08-11 12:21 +0200
        Re: allow line break at operators Yingjie Lan <lanyjie@yahoo.com> - 2011-08-10 19:58 -0700
        Re: allow line break at operators Chris Rebert <clp2@rebertia.com> - 2011-08-10 21:16 -0700
        Re: allow line break at operators Chris Rebert <clp2@rebertia.com> - 2011-08-10 22:07 -0700
        Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-11 09:24 +0100
        Re: allow line break at operators MRAB <python@mrabarnett.plus.com> - 2011-08-11 14:03 +0100
        Re: [Python-ideas] allow line break at operators Matt Joiner <anacrolix@gmail.com> - 2011-08-12 00:28 +1000
          Re: [Python-ideas] allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-12 12:32 +1000
        Re: [Python-ideas] allow line break at operators Jakob Bowyer <jkbbwr@gmail.com> - 2011-08-11 16:42 +0100
        Re: [Python-ideas] allow line break at operators Daniel Greenfeld <pydanny@gmail.com> - 2011-08-11 10:04 -0700
        Re: [Python-ideas] allow line break at operators Paul Colomiets <paul@colomiets.name> - 2011-08-11 22:17 +0300
        Re: [Python-ideas] allow line break at operators Devin Jeanpierre <jeanpierreda@gmail.com> - 2011-08-11 17:06 -0400
        Re: [Python-ideas] allow line break at operators Devin Jeanpierre <jeanpierreda@gmail.com> - 2011-08-11 17:29 -0400
        Re: [Python-ideas] allow line break at operators Jim Jewett <jimjjewett@gmail.com> - 2011-08-11 17:39 -0400
        Re: [Python-ideas] allow line break at operators Devin Jeanpierre <jeanpierreda@gmail.com> - 2011-08-11 18:29 -0400
        Re: [Python-ideas] allow line break at operators Matt Joiner <anacrolix@gmail.com> - 2011-09-02 15:33 +1000
          Re: [Python-ideas] allow line break at operators Roy Smith <roy@panix.com> - 2011-09-03 12:59 -0400
        Re: [Python-ideas] allow line break at operators "Stephen J. Turnbull" <stephen@xemacs.org> - 2011-09-02 16:28 +0900
        Re: [Python-ideas] allow line break at operators Guido van Rossum <guido@python.org> - 2011-09-02 12:30 -0700
        Re: [Python-ideas] allow line break at operators "Stephen J. Turnbull" <stephen@xemacs.org> - 2011-09-03 13:38 +0900
        Re: [Python-ideas] allow line break at operators "Stephen J. Turnbull" <stephen@xemacs.org> - 2011-09-03 15:10 +0900
        Re: [Python-ideas] allow line break at operators Terry Reedy <tjreedy@udel.edu> - 2011-09-03 15:01 -0400
        Re: [Python-ideas] allow line break at operators ron3200 <ron3200@gmail.com> - 2011-09-04 10:22 -0500
          Re: allow line break at operators rantingrick <rantingrick@gmail.com> - 2011-09-04 11:08 -0700
      Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-11 00:37 +1000
        Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-10 16:13 +0100
        Re: allow line break at operators Ian Kelly <ian.g.kelly@gmail.com> - 2011-08-10 09:16 -0600
          Re: allow line break at operators Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-11 09:32 +1000
            Re: allow line break at operators Chris Angelico <rosuav@gmail.com> - 2011-08-11 00:55 +0100

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