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Re: global/static variables & loops

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James Kuyper <jameskuyper@verizon.net> writes:

> On 02/15/2012 12:25 PM, Anders Wegge Keller wrote:

>>  That is global state in my book.
 
> If that counts as global state, then storing global state in global
> variables is clearly not necessary.

 No, but when the effect is the same anyway, why add another level of
complexity?
 
>>  My point is that no matter how you try to hide it, whether it's to
>> get rid of global variables, just because they are baaad, ...
 
> Your use of "just" and "baaad" implies that you think that the idea
> that globals are bad is an unjustified prejudice,

 It very often is an unreflected, almost religious observance. Just
like "gotos are bad". The next thing you see, is people mechanically
replacing a global variable with a static, and adding getters and
setters because the same state is still needed globally. 

> rather than the well-justified judgment that it actually is.

 If it quacks like a duck, walks like a duck and swims like a duck, it
probably is a duck, no matter how you dress it up. 

> Are you actually unaware of the problems that they can cause?

 If people write bad code, they will get into trouble, no matter what
paradigm they adhere to. I can think of lots of ways a program can
become difficult to manage by doing something stupid with a
global. But that is not exclusive to that style.

>> ... or if you actually need to do something in a smarter way, there
>> is hardly a program that hasn't got a global state. And in that
>> case, I fail to see why the program would be any worse, by actually
>> admitting the fact.

> The key problem with global variables is visibility; by being
> visible everywhere, they can be affected by anything, which can make
> it difficult to determine what part of the program caused those
> variables to have their current value, or what part had it's
> behavior affected by the value.

 Scratch the getter/setter pattern, and the global struct pointer
that's passed down the call tree then. *OR* prototype the darn things
as const outside the translation unit that actually has to modify
them, and see where the compiler complains. (And remember to remove
the const prototype afterwards, unless you want to see some
spectacular failures :)

> Variables which are local to main() and are passed by a
> pointer to subroutines need not be passed to all subroutines, but only
> the ones that actually need to have access to those variables, and that
> could be a different set of subroutines for different variables. 

 Unless you have a very limited state space, that will lead to some
very convoluted and error-prone code. 

> Making information available to a subroutine only on a "need to
> know" basis is good software design. It can be overdone, but that's
> seldom a real-world problem.

 You should try to do real-time machine control with 10-15
co-concurrent tasks running on a 80186 platform, where each individual
thread has a stack in the range 128 to 256 bytes, and avoid overdoing
need-to-know :) I'm in the 0.1%, where overdoing things are a
real-world problem.

-- 
/Wegge

Leder efter redundant peering af dk.*,linux.debian.*

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global/static variables & loops Rob Janecek <robs@invalid.com> - 2012-02-14 19:56 +0000
  Re: global/static variables & loops Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-14 12:42 -0800
  Re: global/static variables & loops Stephen Sprunk <stephen@sprunk.org> - 2012-02-14 15:01 -0600
  Re: global/static variables & loops Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-14 20:35 -0500
    Re: global/static variables & loops Philip Lantz <prl@canterey.us> - 2012-02-14 21:18 -0800
    Re: global/static variables & loops pete <pfiland@mindspring.com> - 2012-02-15 00:53 -0500
      Re: global/static variables & loops Jonathan Leffler <jleffler@earthlink.net> - 2012-02-18 21:15 -0800
        Re: global/static variables & loops Kaz Kylheku <kaz@kylheku.com> - 2012-02-19 06:05 +0000
          Re: global/static variables & loops Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-22 03:15 +0200
        Re: global/static variables & loops Shao Miller <sha0.miller@gmail.com> - 2012-02-19 04:14 -0500
          Re: global/static variables & loops Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-19 12:32 +0000
            Re: Array 'typedef's and exclusive use of '->' versus '.' Shao Miller <sha0.miller@gmail.com> - 2012-02-19 17:00 -0500
              Re: Array 'typedef's and exclusive use of '->' versus '.' Keith Thompson <kst-u@mib.org> - 2012-02-19 16:43 -0800
                Re: Array 'typedef's and exclusive use of '->' versus '.' Shao Miller <sha0.miller@gmail.com> - 2012-02-19 20:32 -0500
              Re: Array 'typedef's and exclusive use of '->' versus '.' Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-22 03:27 +0200
                Re: Array 'typedef's and exclusive use of '->' versus '.' Shao Miller <sha0.miller@gmail.com> - 2012-02-25 02:19 -0500
                Re: Array 'typedef's and exclusive use of '->' versus '.' Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-25 10:14 +0200
    Re: global/static variables & loops "BartC" <bc@freeuk.com> - 2012-02-15 10:47 +0000
      Re: global/static variables & loops Kaz Kylheku <kaz@kylheku.com> - 2012-02-15 11:42 +0000
        Re: global/static variables & loops "BartC" <bc@freeuk.com> - 2012-02-15 12:54 +0000
        Re: global/static variables & loops Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-15 05:17 -0800
      Re: global/static variables & loops Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-22 03:28 +0200
    Re: global/static variables & loops August Karlstrom <fusionfile@gmail.com> - 2012-02-15 15:19 +0100
    Re: global/static variables & loops Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-22 03:12 +0200
  Re: global/static variables & loops Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-15 01:23 -0800
    Re: global/static variables & loops August Karlstrom <fusionfile@gmail.com> - 2012-02-15 14:03 +0100
      Re: global/static variables & loops Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-15 05:20 -0800
        Re: global/static variables & loops James Kuyper <jameskuyper@verizon.net> - 2012-02-15 08:41 -0500
          Re: global/static variables & loops Kaz Kylheku <kaz@kylheku.com> - 2012-02-16 00:20 +0000
            Re: global/static variables & loops Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-15 21:02 -0500
              Re: global/static variables & loops "BartC" <bc@freeuk.com> - 2012-02-16 10:03 +0000
                Re: global/static variables & loops Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-16 07:58 -0500
              Re: global/static variables & loops Markus Wichmann <nullplan@gmx.net> - 2012-02-19 20:44 +0100
                Re: global/static variables & loops Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-19 15:37 -0500
                Re: global/static variables & loops Kaz Kylheku <kaz@kylheku.com> - 2012-02-22 05:01 +0000
                Re: global/static variables & loops Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-22 08:12 -0500
    Re: global/static variables & loops Anders Wegge Keller <wegge@wegge.dk> - 2012-02-15 15:55 +0100
      Re: global/static variables & loops James Kuyper <jameskuyper@verizon.net> - 2012-02-15 11:05 -0500
      Re: global/static variables & loops Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-15 09:13 -0800
        Re: global/static variables & loops Anders Wegge Keller <wegge@wegge.dk> - 2012-02-15 18:25 +0100
          Re: global/static variables & loops James Kuyper <jameskuyper@verizon.net> - 2012-02-15 13:25 -0500
            Re: global/static variables & loops Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-15 10:51 -0800
              Re: global/static variables & loops James Kuyper <jameskuyper@verizon.net> - 2012-02-15 14:45 -0500
              Re: global/static variables & loops Anders Wegge Keller <wegge@wegge.dk> - 2012-02-15 20:47 +0100
                Re: global/static variables & loops Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-16 04:45 -0800
                Re: global/static variables & loops Anders Wegge Keller <wegge@wegge.dk> - 2012-02-16 14:25 +0100
                Re: global/static variables & loops Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-16 08:10 -0800
                Re: global/static variables & loops Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-17 00:59 -0800
            Re: global/static variables & loops Anders Wegge Keller <wegge@wegge.dk> - 2012-02-15 20:30 +0100
              Re: global/static variables & loops James Kuyper <jameskuyper@verizon.net> - 2012-02-15 15:00 -0500
                Re: global/static variables & loops Anders Wegge Keller <wegge@wegge.dk> - 2012-02-15 21:30 +0100
                Re: global/static variables & loops James Kuyper <jameskuyper@verizon.net> - 2012-02-15 16:00 -0500
                Re: global/static variables & loops Anders Wegge Keller <wegge@wegge.dk> - 2012-02-15 23:10 +0100
                Re: global/static variables & loops Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-15 15:50 -0800
                Re: global/static variables & loops James Kuyper <jameskuyper@verizon.net> - 2012-02-15 19:50 -0500
                Re: global/static variables & loops Anders Wegge Keller <wegge@wegge.dk> - 2012-02-16 14:36 +0100
            Re: global/static variables & loops Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-16 03:29 -0800
      Re: global/static variables & loops Anders Wegge Keller <wegge@wegge.dk> - 2012-02-15 23:37 +0100
      Re: global/static variables & loops Kaz Kylheku <kaz@kylheku.com> - 2012-02-16 00:23 +0000
        Re: global/static variables & loops Anders Wegge Keller <wegge@wegge.dk> - 2012-02-16 01:29 +0100
        Re: global/static variables & loops Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-15 21:20 -0500
      Re: global/static variables & loops Shao Miller <sha0.miller@gmail.com> - 2012-02-15 22:24 -0500
        Re: global/static variables & loops Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-16 01:08 -0800
      Re: global/static variables & loops Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-16 03:17 -0800

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