Re: Regression testing for pointers

From	Malcolm McLean <malcolm.mclean5@btinternet.com>
Newsgroups	comp.lang.c
Subject	Re: Regression testing for pointers
Date	2012-03-14 15:15 -0700
Organization	http://groups.google.com
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בתאריך יום רביעי, 14 במרס 2012 08:45:26 UTC, מאת Don Y:
> Oh, I think I see the distinction you are making.  To you,
> a "pure function" can have no side effects.  It takes
> inputs using call by value semantics and returns a result
> maintaining no internal state in the process.
> 
A function is a mapping of input to output. A procedure is is a sequence of actions. Unfortunately these terms are in use to refer to void fucntions and those that return values. This distinction is important for the grammar of the language (if(foo()) is illegal if foo is a void fucntion, legal if it return a value), but not from a softwar eengineering perspective (rewrite int foo(void) as void foo(int *answer) and you're not really changing anything.) 

A pure function changes the dta passed to it, but nothing else. That means that, strictly, it can't call malloc(). Even if it just allocates a temporary buffer and frees it, that may change the state of the heap and cause the next call to malloc() to return null when it otherwise wouldn't have done, so not a pure function.
But that requirement means that a large number of functions either have to be declared non-pure, or they have to use fixed buffers and return buffer exceeded errors. That's not really useful. So it's better to divide your functions into those that do IO and those that don't. That's the best palce to do the division. But it does make malloc() a special function.

-- 
Basic Algorithms - fast allocators, and how to implement your own malloc()
http://www.malcolmmclean.site11.com/www

Thread

Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-09 16:43 -0700
  Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-10 12:56 +1300
    Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-09 19:40 -0700
      Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-10 17:53 +1300
        Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-10 18:12 +1300
        Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-10 02:05 -0700
          Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-10 23:17 +1300
            Re: Regression testing for pointers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-03-10 12:00 +0000
              Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-11 11:00 +1300
                Re: Regression testing for pointers Ike Naar <ike@iceland.freeshell.org> - 2012-03-10 22:23 +0000
                Re: Regression testing for pointers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-03-10 22:40 +0000
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-11 12:12 +1300
                Re: Regression testing for pointers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-03-11 00:42 +0000
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-11 14:26 +1300
                Re: Regression testing for pointers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-03-11 03:09 +0000
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-11 18:16 +1300
            Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-10 12:01 -0700
              Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-11 10:35 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-12 09:19 -0700
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-13 07:23 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-12 16:23 -0700
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-13 17:25 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-13 00:19 -0700
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-13 20:34 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-13 01:00 -0700
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-13 21:22 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-13 10:19 -0700
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-14 07:25 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-14 02:00 -0700
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-14 22:18 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-14 11:32 -0700
                Re: Regression testing for pointers nick_keighley_nospam@hotmail.com - 2012-03-15 05:58 -0700
                Re: Regression testing for pointers nick_keighley_nospam@hotmail.com - 2012-03-15 05:55 -0700
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-15 11:32 -0700
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-16 18:14 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-20 01:43 -0700
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-20 21:59 +1300
                Re: Regression testing for pointers nick_keighley_nospam@hotmail.com - 2012-03-16 03:05 -0700
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-20 02:33 -0700
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-24 11:49 +1300
          Re: Regression testing for pointers nick_keighley_nospam@hotmail.com - 2012-03-11 05:01 -0700
            Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-11 09:44 -0700
              Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-12 09:56 +1300
    Re: Regression testing for pointers nick_keighley_nospam@hotmail.com - 2012-03-10 02:28 -0800
      Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-10 11:09 -0700
      Re: Regression testing for pointers Kaz Kylheku <kaz@kylheku.com> - 2012-03-10 18:29 +0000
        Re: Regression testing for pointers nick_keighley_nospam@hotmail.com - 2012-03-11 05:22 -0700
          Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-11 09:50 -0700
            Re: Regression testing for pointers "io_x" <a@b.c.invalid> - 2012-03-13 13:09 +0100
  Re: Regression testing for pointers Kaz Kylheku <kaz@kylheku.com> - 2012-03-10 03:14 +0000
    Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-10 12:42 -0700
  Re: Regression testing for pointers Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-03-10 08:42 +0000
    Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-10 02:19 -0700
      Re: Regression testing for pointers "BartC" <bc@freeuk.com> - 2012-03-10 15:54 +0000
        Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-10 11:49 -0700
          Re: Regression testing for pointers nick_keighley_nospam@hotmail.com - 2012-03-11 06:09 -0700
            Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-11 12:33 -0700
              Re: Regression testing for pointers nick_keighley_nospam@hotmail.com - 2012-03-12 03:29 -0700
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-12 10:01 -0700
                Re: Regression testing for pointers "BartC" <bc@freeuk.com> - 2012-03-13 18:56 +0000
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-13 16:31 -0700
      Re: Regression testing for pointers Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-03-12 00:30 +0000
        Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-12 16:41 -0700
      Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-12 13:39 +1300
        Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-12 09:36 -0700
          Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-13 07:25 +1300
            Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-12 16:28 -0700
              Re: Regression testing for pointers Kaz Kylheku <kaz@kylheku.com> - 2012-03-13 04:20 +0000
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-13 17:34 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-13 00:29 -0700
              Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-13 17:31 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-13 01:05 -0700
                Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-13 21:30 +1300
                Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-13 10:43 -0700
  Re: Regression testing for pointers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-10 15:41 -0800
    Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-11 11:23 -0700
      Re: Regression testing for pointers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-13 13:43 -0700
        Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-14 01:45 -0700
          Re: Regression testing for pointers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-14 15:15 -0700
            Re: Regression testing for pointers Kaz Kylheku <kaz@kylheku.com> - 2012-03-14 22:57 +0000
              Re: Regression testing for pointers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-15 13:10 -0700
                Re: Regression testing for pointers jgk@panix.com (Joe keane) - 2012-03-16 22:20 +0000
                Re: Regression testing for pointers "io_x" <a@b.c.invalid> - 2012-03-18 07:15 +0100
            Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-14 23:13 -0700
  Re: Regression testing for pointers gordonb.b29ri@burditt.org (Gordon Burditt) - 2012-03-12 19:37 -0500
    Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-12 19:23 -0700
  Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-14 13:12 +1300
    Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-14 01:54 -0700
      Re: Regression testing for pointers Ian Collins <ian-news@hotmail.com> - 2012-03-14 22:05 +1300
        Re: Regression testing for pointers Don Y <this@isnotme.com> - 2012-03-14 11:54 -0700

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