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

Path csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Subject Re: Problems using struct pack/unpack in files, and reading them.
Date Sun, 15 Nov 2015 04:04:18 +1100
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On Sun, Nov 15, 2015 at 3:52 AM, Marko Rauhamaa <marko@pacujo.net> wrote:
> What I don't understand is why there is a unary + but no unary /:
>
>    -x ≡ 0 - x
>    +x ≡ 0 + x
>    /x ≡ 1 / x
>    //x ≡ 1 // x
>    *x ≡ 1 * x
>
> You could write:
>
>    r = //(//r1 + //r2 + //r3)
>
> for
>
>    r = 1 // (1//r1 + 1//r2 + 1//r3)

Small problem: Since we have / and // operators, it's impossible to
have a unary / operator:

1 // x
1 / (/x)

But leaving that aside, the number of times you'd want this are far
fewer than the times you want unary minus.

> Actually, the real question is, is the unary - *really* so useful that
> it merits existence or is it just something that was mindlessly copied
> into programming languages from elementary school arithmetics?

More likely, copied from C. But that's why I made my other post.

ChrisA

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Thread

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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