Re: template metaprogramming in C?

From	Malcolm McLean <malcolm.mclean5@btinternet.com>
Newsgroups	comp.lang.c
Subject	Re: template metaprogramming in C?
Date	2012-03-24 07:25 -0700
Organization	http://groups.google.com
Message-ID	<15270245.366.1332599106789.JavaMail.geo-discussion-forums@vbgx21> (permalink)
References	<jkkcqp$b94$1@speranza.aioe.org>

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בתאריך יום שבת, 24 במרס 2012 11:57:11 UTC, מאת Rui Maciel:
> What are your thoughts on adding a standard form of proper template 
> metaprogramming to the C programming language? 
> 
>
Standards mean that every plug fits every socket, but only it it's compatible. So a British 3 pin plug with square pins will fit any British mains socket. But it won't fit an American socket, and rightly, because American mains voltage is different and you might damage equipment.

Now in programming, think of the data as the plug and the function interface as the socket. We want any data held be caller to be passed into callee, but only if it's compatible.
So say someone writes

double mean(double *x, int N);

That's not very good if our data is floats, or integers, or if it's the 'salary' field of an array of struct employees. We've got to write special adapter fucntions, just to get the data into a suitable format to pass to mean.

But there are huge problems with a template approach. If we call mean() on an array of floats, we would expect a float back. But the mean of an array of integers is not necessarily an integer. The mean of an array of long doubles or some custome huge integer type might not be representable in double.
Then if you've got a really low precision float type, really you need to sort the input first before summing it. This is likely to be overkill for normal use, however.
There are all sorts of problems, even with this extremely simple function. The problem with templates is that most template systems don't really address these issues. They mean that the function can be passed a double *, int *, or float *, but that's a small win.

-- 
Basic Algorithms - a massive compendium of C programming resources.
http://www.malcolmmclean.site11.com/www

Thread

template metaprogramming in C? Rui Maciel <rui.maciel@gmail.com> - 2012-03-24 11:57 +0000
  Re: template metaprogramming in C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-24 07:25 -0700
    Re: template metaprogramming in C? Markus Wichmann <nullplan@gmx.net> - 2012-03-26 11:46 +0200
      Re: template metaprogramming in C? Philipp Klaus Krause <pkk@spth.de> - 2012-03-27 21:09 +0200
        Re: template metaprogramming in C? Markus Wichmann <nullplan@gmx.net> - 2012-03-28 09:25 +0200
          Re: template metaprogramming in C? James Kuyper <jameskuyper@verizon.net> - 2012-03-28 06:59 -0400
      Re: template metaprogramming in C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-28 12:13 -0700
      Re: template metaprogramming in C? James Dow Allen <jdallen2000@yahoo.com> - 2012-04-01 02:47 -0700
  Re: template metaprogramming in C? Jens Gustedt <jens.gustedt@loria.fr> - 2012-03-24 18:01 +0100
  Re: template metaprogramming in C? Nobody <nobody@nowhere.com> - 2012-03-24 22:57 +0000
    Re: template metaprogramming in C? William Ahern <william@wilbur.25thandClement.com> - 2012-03-24 18:29 -0700
      Re: template metaprogramming in C? Ian Collins <ian-news@hotmail.com> - 2012-03-25 15:03 +1300
      Re: template metaprogramming in C? nick_keighley_nospam@hotmail.com - 2012-03-25 05:32 -0700
  Re: template metaprogramming in C? BGB <cr88192@hotmail.com> - 2012-03-24 17:02 -0700
  Re: template metaprogramming in C? jacob navia <jacob@spamsink.net> - 2012-03-25 01:21 +0100
    Re: template metaprogramming in C? Philipp Klaus Krause <pkk@spth.de> - 2012-03-27 21:17 +0200
      Re: template metaprogramming in C? jacob navia <jacob@spamsink.net> - 2012-03-28 11:10 +0200
        Re: template metaprogramming in C? Nils M Holm <news2009@t3x.org> - 2012-03-28 10:05 +0000
          Re: template metaprogramming in C? Willem <willem@toad.stack.nl> - 2012-03-28 13:36 +0000
            Re: template metaprogramming in C? Nils M Holm <news2009@t3x.org> - 2012-03-28 14:40 +0000
        Re: template metaprogramming in C? Kaz Kylheku <kaz@kylheku.com> - 2012-03-28 18:32 +0000
          Re: template metaprogramming in C? jacob navia <jacob@spamsink.net> - 2012-03-28 22:27 +0200
            Re: template metaprogramming in C? Kaz Kylheku <kaz@kylheku.com> - 2012-03-28 21:02 +0000
        Re: template metaprogramming in C? Nobody <nobody@nowhere.com> - 2012-03-29 16:30 +0100
          Re: template metaprogramming in C? jacob navia <jacob@spamsink.net> - 2012-03-29 23:39 +0200
            Re: template metaprogramming in C? "BartC" <bc@freeuk.com> - 2012-03-29 23:36 +0100
              Re: template metaprogramming in C? Kaz Kylheku <kaz@kylheku.com> - 2012-03-30 00:55 +0000
            Re: template metaprogramming in C? Kaz Kylheku <kaz@kylheku.com> - 2012-03-30 00:32 +0000
              Re: template metaprogramming in C? "BartC" <bc@freeuk.com> - 2012-03-30 10:52 +0100
                Re: template metaprogramming in C? jacob navia <jacob@spamsink.net> - 2012-04-01 09:36 +0200
            Re: template metaprogramming in C? Ian Collins <ian-news@hotmail.com> - 2012-03-30 16:32 +1300
              Re: template metaprogramming in C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-31 01:52 -0700
    Re: template metaprogramming in C? ImpalerCore <jadill33@gmail.com> - 2012-03-28 08:48 -0700
      Re: template metaprogramming in C? "io_x" <a@b.c.invalid> - 2012-04-05 12:18 +0200
        Re: template metaprogramming in C? "io_x" <a@b.c.invalid> - 2012-04-05 13:08 +0200
          Re: template metaprogramming in C? "io_x" <a@b.c.invalid> - 2012-04-05 13:36 +0200
            Re: template metaprogramming in C? pete <pfiland@mindspring.com> - 2012-04-06 18:43 -0400
              Re: template metaprogramming in C? pete <pfiland@mindspring.com> - 2012-04-06 19:20 -0400
      Re: template metaprogramming in C? "io_x" <a@b.c.invalid> - 2012-04-05 13:08 +0200
  Re: template metaprogramming in C? William Ahern <william@wilbur.25thandClement.com> - 2012-03-24 19:01 -0700
    Re: template metaprogramming in C? William Ahern <william@wilbur.25thandClement.com> - 2012-03-24 19:10 -0700
  Re: template metaprogramming in C? Ian Collins <ian-news@hotmail.com> - 2012-03-25 15:25 +1300
    Re: template metaprogramming in C? Rui Maciel <rui.maciel@gmail.com> - 2012-03-25 15:13 +0100
      Re: template metaprogramming in C? Ian Collins <ian-news@hotmail.com> - 2012-03-26 07:10 +1300
        Re: template metaprogramming in C? Rui Maciel <rui.maciel@gmail.com> - 2012-03-25 20:31 +0100
          Re: template metaprogramming in C? nick_keighley_nospam@hotmail.com - 2012-03-26 00:54 -0700

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