Re: Python handles globals badly.

From	"Skybuck Flying" <skybuck2000@hotmail.com>
Newsgroups	comp.lang.python
References	(6 earlier) <CALwzidkyAEGiLT--0XpFesmCv8yM6S9t-JXVLJsBTN0UoWGmhA@mail.gmail.com> <55EF1DD9.8080705@mrabarnett.plus.com> <msno70$vne$1@ger.gmane.org> <55EF6D3B.6030106@mrabarnett.plus.com> <mailman.242.1441758354.8327.python-list@python.org>
Subject	Re: Python handles globals badly.
Date	2015-09-11 10:23 +0200
Message-ID	<6ddeb$55f28f7d$d47876e2$13291@news.ziggo.nl> (permalink)
Organization	Ziggo

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"Random832"  wrote in message 
news:mailman.242.1441758354.8327.python-list@python.org...

MRAB <python@mrabarnett.plus.com> writes:
> If you're allowed to specify both bounds, why would you be forbidden
> from negative ones?

"
It makes it non-obvious what value should be returned from e.g. search
methods that return a negative number on failure. .NET's IndexOf
function returns -1, but MaxValue if the array has a negative
bound. BinarySearch returns the complement of the nearest index to the
value you were searching for, which requires some gymnastics if you want
to make use of it for an array that has negative and positive bounds.
"

Yes pascal/Delphi allows negative bounds if I recall correctly, example:

var
    vIntegerArray : array[-10..10] of integer;

You have just given a very good reason why to not use negative values for 
return values/indications of success or failure.

In pascal I pretty much always try and use booleans to return success.

This is a smart thing to do... especially in pascal/Delphi, since one never 
knows when one is dealing with negative numbers having processing needs.

-1 could then cause problems/troubles/errors.

There is a drawback of using booleans which I suspect is the real reason why 
C programmers for example like to use -1 to indicate failure.

It's "speed/performance". Using a seperate boolean doubles memory 
requirement and might or might not require extra processing time from the 
CPU.

Delphi usually optimizes these booleans to be returned in EAX register... so 
it's a register based thing... if enough registers or so are available 
otherwise perhaps
some pushes/pops needed... not sure about that last thing. Whatever the case 
may be... I will assume for now... that nowadays the performance impact of 
using booleans
as return values is not that great ? Also I am not sure... but perhaps 
booleans allow safer/better procesing of boolean operations.

Not sure how -1 or if -1 could lead to problems with or/and statements... 
mixing C function results will also become problematic... sometimes C 
functions return 0 to indicate failure.

Sometimes 0 can even mean success.

So C is pretty inconsistent when it comes to return values.

Hence I believe Pascal/Delphi to be better/safer at this.

Bye,
  Skybuck.

Thread

Re: Python handles globals badly. tdev@freenet.de - 2015-09-02 11:47 -0700
  Re: Python handles globals badly. tdev@freenet.de - 2015-09-02 12:32 -0700
  Re: Python handles globals badly. Emile van Sebille <emile@fenx.com> - 2015-09-02 12:34 -0700
  Re: Python handles globals badly. Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-02 13:38 -0600
  Re: Python handles globals badly. "Sven R. Kunze" <srkunze@mail.de> - 2015-09-02 22:08 +0200
  Re: Python handles globals badly. MRAB <python@mrabarnett.plus.com> - 2015-09-02 21:22 +0100
  Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-02 22:19 +0100
  Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-03 02:16 +0100
  Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-03 11:49 +1000
  Re: Python handles globals badly. Vladimir Ignatov <kmisoft@gmail.com> - 2015-09-04 20:05 -0400
  Re: Python handles globals badly. Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2015-09-08 10:40 +0200
  Re: Python handles globals badly. Vladimir Ignatov <kmisoft@gmail.com> - 2015-09-08 07:55 -0400
  Re: Python handles globals badly. Akira Li <4kir4.1i@gmail.com> - 2015-09-08 15:35 +0300
  Re: Python handles globals badly. Mario Figueiredo <marfig@gmx.com> - 2015-09-08 14:05 +0100
  Re: Python handles globals badly. Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-08 08:31 -0600
    Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-09 01:56 +1000
      Re: Python handles globals badly. Michael Torrie <torriem@gmail.com> - 2015-09-08 17:55 -0600
        Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-09 13:23 +1000
          Re: Python handles globals badly. Christian Gollwitzer <auriocus@gmx.de> - 2015-09-09 18:09 +0200
            Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-10 03:22 +1000
              Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-10 03:27 +1000
              Re: Python handles globals badly. William Ray Wing <wrw@mac.com> - 2015-09-09 13:59 -0400
              Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-09 20:20 +0100
                Re: Python handles globals badly. Peter Pearson <pkpearson@nowhere.invalid> - 2015-09-10 20:49 +0000
              Re: Python handles globals badly. MRAB <python@mrabarnett.plus.com> - 2015-09-09 20:22 +0100
              Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-10 05:27 +1000
      Re: Python handles globals badly. Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2015-09-09 12:42 +0200
      Re: Python handles globals badly. Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-09-09 09:33 -0400
  Re: Python handles globals badly. random832@fastmail.us - 2015-09-08 12:13 -0400
  Re: Python handles globals badly. MRAB <python@mrabarnett.plus.com> - 2015-09-08 18:41 +0100
  Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-08 23:41 +0100
  Re: Python handles globals badly. MRAB <python@mrabarnett.plus.com> - 2015-09-09 00:20 +0100
  Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-09 00:32 +0100
  Re: Python handles globals badly. Random832 <random832@fastmail.com> - 2015-09-08 20:02 -0400
    Re: Python handles globals badly. "Skybuck Flying" <skybuck2000@hotmail.com> - 2015-09-11 10:23 +0200
  Re: Python handles globals badly. Mario Figueiredo <marfig@gmx.com> - 2015-09-09 02:09 +0100
    Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-10 03:55 +1000
      Re: Python handles globals badly. Laura Creighton <lac@openend.se> - 2015-09-09 20:05 +0200
      Re: Python handles globals badly. Emile van Sebille <emile@fenx.com> - 2015-09-09 11:23 -0700
        Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-10 22:20 +1000
      Re: Python handles globals badly. "Sven R. Kunze" <srkunze@mail.de> - 2015-09-09 20:26 +0200
        Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-11 01:50 +1000
      Re: Python handles globals badly. random832@fastmail.us - 2015-09-09 14:59 -0400
        Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-11 01:59 +1000
          Re: Python handles globals badly. random832@fastmail.us - 2015-09-10 12:31 -0400
            Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-11 04:13 +1000
              Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-11 04:33 +1000
              Re: Python handles globals badly. Jussi Piitulainen <harvesting@makes.email.invalid> - 2015-09-10 22:11 +0300
              Re: Python handles globals badly. random832@fastmail.us - 2015-09-10 16:30 -0400
          Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-11 02:48 +1000
          Re: Python handles globals badly. alister <alister.nospam.ware@ntlworld.com> - 2015-09-10 19:56 +0000
          Re: Python handles globals badly. random832@fastmail.us - 2015-09-10 16:07 -0400
          Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-11 11:35 +1000
          Re: Python handles globals badly. Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2015-09-11 12:19 +0200
            Re: Python handles globals badly. Marko Rauhamaa <marko@pacujo.net> - 2015-09-11 14:59 +0300
              Re: Python handles globals badly. Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2015-09-14 09:13 +0200
      Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-10 05:00 +1000
      Re: Python handles globals badly. Laura Creighton <lac@openend.se> - 2015-09-09 21:14 +0200
      Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-10 05:18 +1000
        Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-10 22:18 +1000
          Re: Python handles globals badly. jkn <jkn_gg@nicorp.f9.co.uk> - 2015-09-10 08:09 -0700
          Re: Python handles globals badly. rurpy@yahoo.com - 2015-09-10 12:04 -0700
            Re: Python handles globals badly. Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-09-10 20:33 -0400
            Re: Python handles globals badly. Gene Heskett <gheskett@wdtv.com> - 2015-09-10 22:19 -0400
            Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-12 03:35 +0100
            Re: Python handles globals badly. Mario Figueiredo <marfig@gmx.com> - 2015-09-12 05:11 +0100
            Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-12 05:38 +0100
            Re: Python handles globals badly. Mario Figueiredo <marfig@gmx.com> - 2015-09-12 16:52 +0100
            Re: Python handles globals badly. Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-09-12 12:24 -0400
            Re: Python handles globals badly. Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-09-12 12:29 -0400
            Re: Python handles globals badly. MRAB <python@mrabarnett.plus.com> - 2015-09-12 18:09 +0100
            Re: Python handles globals badly. Mario Figueiredo <marfig@gmx.com> - 2015-09-12 22:57 +0100
            Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-12 23:05 +0100
            Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-12 23:07 +0100
      Re: Python handles globals badly. "Sven R. Kunze" <srkunze@mail.de> - 2015-09-09 21:21 +0200
      Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-09 20:24 +0100
      Re: Python handles globals badly. Mario Figueiredo <marfig@gmx.com> - 2015-09-09 20:57 +0100
      Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-09 21:15 +0100
      Re: Python handles globals badly. Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2015-09-10 09:27 +0200
        Re: Python handles globals badly. Marko Rauhamaa <marko@pacujo.net> - 2015-09-10 10:49 +0300
      Re: Python handles globals badly. Michael Torrie <torriem@gmail.com> - 2015-09-10 08:21 -0600
      Re: Python handles globals badly. Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2015-09-11 09:28 +0200
        Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-12 13:48 +1000
          Re: Python handles globals badly. Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2015-09-14 10:30 +0200
            Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-16 11:13 +1000
              Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-16 11:20 +1000
                Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-16 11:58 +1000
              Re: Python handles globals badly. Random832 <random832@fastmail.com> - 2015-09-15 21:54 -0400
              Re: Python handles globals badly. Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2015-09-16 10:51 +0200
      Re: Python handles globals badly. random832@fastmail.us - 2015-09-11 08:50 -0400
  Re: Python handles globals badly. Ben Finney <ben+python@benfinney.id.au> - 2015-09-09 11:26 +1000
  Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-09 11:41 +1000
  Re: Python handles globals badly. Mario Figueiredo <marfig@gmx.com> - 2015-09-09 03:43 +0100
  Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-09 13:03 +1000
  Re: Python handles globals badly. Ben Finney <ben+python@benfinney.id.au> - 2015-09-09 15:53 +1000

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