Re: Problems using struct pack/unpack in files, and reading them.

From	Chris Angelico <rosuav@gmail.com>
Newsgroups	comp.lang.python
Subject	Re: Problems using struct pack/unpack in files, and reading them.
Date	2015-11-15 03:59 +1100
Message-ID	<mailman.332.1447520400.16136.python-list@python.org> (permalink)
References	(2 earlier) <mailman.310.1447454532.16136.python-list@python.org> <56469f14$0$1612$c3e8da3$5496439d@news.astraweb.com> <mailman.314.1447470111.16136.python-list@python.org> <5646c95a$0$1597$c3e8da3$5496439d@news.astraweb.com> <CALwzidnYYiErH_ERYCszk6eyxcv13eV08=6PpXHDj25iSmre8Q@mail.gmail.com>

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On Sun, Nov 15, 2015 at 2:43 AM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> On Fri, Nov 13, 2015 at 10:40 PM, Steven D'Aprano <steve@pearwood.info> wrote:
>> Python has operator overloading, so it can be anything you want it to be.
>> E.g. you might have a DSL where +feature turns something on and -feature
>> turns it off.
>
> By that argument we should also have operators ~, !, $, \, ? because
> some hypothetical DSL might someday want to use them for something.

Unary tilde does, doing bitwise negation on integers. Backslash
probably never will, due to confusion with line continuation and
stuff. But let's look at the parallel-universe Python in which unary
plus never existed (but unary minus did). The PEP preamble for its
inclusion says:

Abstract
This PEP proposes a new unary version of the binary + operator.

Specification
A new unary operator is added to the Python language:
=======  ========================= ===========
 Op      Precedence/associativity     Method
=======  ========================= ===========
``+``    Same as unary ``-``       ``__pos__``
=======  ========================= ===========

No implementations of this methods is added to the builtin or standard
library types. However, we foresee that Domain-Specific Languages can
make use of this parallel to unary minus; see Intended usage details
below for details.

Okay. I've done my bit, stealing text from PEP 465. Now Steven, you
can write the Motivation section. There's a lot of similarities here
(Python's built-in types do not need @ or unary + for anything), but
the big push for 465 was that there have been calls for the new
operator for years. So... where would the "please add unary plus"
calls come from?

ChrisA

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Re: Problems using struct pack/unpack in files, and reading them. Chris Angelico <rosuav@gmail.com> - 2015-11-14 09:42 +1100
  Re: Problems using struct pack/unpack in files, and reading them. Steven D'Aprano <steve@pearwood.info> - 2015-11-14 13:40 +1100
    Re: Problems using struct pack/unpack in files, and reading them. Chris Angelico <rosuav@gmail.com> - 2015-11-14 14:01 +1100
      Re: Problems using struct pack/unpack in files, and reading them. Steven D'Aprano <steve@pearwood.info> - 2015-11-14 16:40 +1100
        Re: Problems using struct pack/unpack in files, and reading them. Ian Kelly <ian.g.kelly@gmail.com> - 2015-11-14 08:43 -0700
          Re: Problems using struct pack/unpack in files, and reading them. Marko Rauhamaa <marko@pacujo.net> - 2015-11-14 18:52 +0200
            Re: Problems using struct pack/unpack in files, and reading them. Chris Angelico <rosuav@gmail.com> - 2015-11-15 04:04 +1100
              Re: Problems using struct pack/unpack in files, and reading them. Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-11-16 19:19 +1300
            Re: Problems using struct pack/unpack in files, and reading them. Ian Kelly <ian.g.kelly@gmail.com> - 2015-11-14 10:04 -0700
              Re: Problems using struct pack/unpack in files, and reading them. Marko Rauhamaa <marko@pacujo.net> - 2015-11-14 23:53 +0200
              Re: Problems using struct pack/unpack in files, and reading them. Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-11-16 19:15 +1300
                Re: Problems using struct pack/unpack in files, and reading them. Steven D'Aprano <steve@pearwood.info> - 2015-11-16 23:11 +1100
                Re: Problems using struct pack/unpack in files, and reading them. Dave Farrance <df@see.replyto.invalid> - 2015-11-17 09:54 +0000
            Re: Problems using struct pack/unpack in files, and reading them. Ian Kelly <ian.g.kelly@gmail.com> - 2015-11-14 10:13 -0700
            Re: Problems using struct pack/unpack in files, and reading them. Random832 <random832@fastmail.com> - 2015-11-14 17:53 -0500
              Re: Problems using struct pack/unpack in files, and reading them. Marko Rauhamaa <marko@pacujo.net> - 2015-11-15 02:12 +0200
              Re: Problems using struct pack/unpack in files, and reading them. Steven D'Aprano <steve@pearwood.info> - 2015-11-15 12:14 +1100
                Re: Problems using struct pack/unpack in files, and reading them. Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-11-15 11:09 -0500
                Re: Problems using struct pack/unpack in files, and reading them. Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-11-16 19:11 +1300
            Re: Problems using struct pack/unpack in files, and reading them. MRAB <python@mrabarnett.plus.com> - 2015-11-15 00:49 +0000
          Re: Problems using struct pack/unpack in files, and reading them. Steven D'Aprano <steve@pearwood.info> - 2015-11-15 13:08 +1100
            Re: Problems using struct pack/unpack in files, and reading them. Chris Angelico <rosuav@gmail.com> - 2015-11-15 13:23 +1100
              Re: Problems using struct pack/unpack in files, and reading them. Steven D'Aprano <steve@pearwood.info> - 2015-11-17 00:17 +1100
                Re: Problems using struct pack/unpack in files, and reading them. Chris Angelico <rosuav@gmail.com> - 2015-11-17 00:27 +1100
        Re: Problems using struct pack/unpack in files, and reading them. Chris Angelico <rosuav@gmail.com> - 2015-11-15 03:59 +1100
    Re: Problems using struct pack/unpack in files, and reading them. Ian Kelly <ian.g.kelly@gmail.com> - 2015-11-13 20:45 -0700
    Re: Problems using struct pack/unpack in files, and reading them. Ian Kelly <ian.g.kelly@gmail.com> - 2015-11-13 20:48 -0700
    Re: Problems using struct pack/unpack in files, and reading them. Chris Angelico <rosuav@gmail.com> - 2015-11-14 14:56 +1100
    Re: Problems using struct pack/unpack in files, and reading them. Chris Angelico <rosuav@gmail.com> - 2015-11-14 14:57 +1100

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