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Re: template metaprogramming in C?

From Kaz Kylheku <kaz@kylheku.com>
Newsgroups comp.lang.c
Subject Re: template metaprogramming in C?
Date 2012-03-28 18:32 +0000
Organization Aioe.org NNTP Server
Message-ID <20120328110920.211@kylheku.com> (permalink)
References <jkkcqp$b94$1@speranza.aioe.org> <jklodd$n3r$1@speranza.aioe.org> <jkt3o7$f1k$1@solani.org> <jkukir$cvn$1@speranza.aioe.org>

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On 2012-03-28, jacob navia <jacob@spamsink.net> wrote:
> Le 27/03/12 21:17, Philipp Klaus Krause a écrit :
>> On 25.03.2012 01:21, jacob navia wrote:
>>
>>>
>>> The direction I am going is to establish real compile time functions
>>> where you have a rich and controlled environment where you develop your
>>> meta-programs, instead of the incredible limited environment of
>>> templates where you do not have even an if statement!
>>>
>>> […]
>>
>> Looks a lot like macros in Scheme.
>>
>> Philipp
>>
>>
>
> ???
> Scheme macros have if/while statements that allow you to generate code 
> in loops?

In general, Lisp macros have been doing this since the 1960's.

Scheme macros are distinguished by pioneering lexical scoping with automatic
hygiene.  Macro code templates, into which arbitrary user code is inserted, can
simply declare local variables in a straightforward way; yet the inserted code
does not have visibility into these variables. A hidden renaming process
eliminates the potential for a clash.

Common Lisp macros are more "nuts-and-bolts"; hygiene is DIY, but with more
flexibilities.

The object system is based on macros: class defining, method defining.

The standard LOOP macro is an entire sublanguage for iteration, expanded by a
macro, and makes a good macro demo:

 (loop for x in '(1 2 3 5)
       summing (* x x) into sum-of-squares
       counting x into n
       finally (return (sqrt (/ sum-of-squares n))))

  -> 3.122499

View the (implementation-specific, not portable Lisp) expansion:

  (macroexpand '(loop for x in '(1 2 3 5)
                      summing (* x x) into sum-of-squares
                      counting x into n
                      finally (return (sqrt (/ sum-of-squares n)))))

  ->

  (MACROLET ((LOOP-FINISH NIL (SYSTEM::LOOP-FINISH-ERROR)))
   (BLOCK NIL
    (LET ((#:LIST-8731 '(1 2 3 5)))
     (PROGN
      (LET ((X NIL))
       (LET ((N 0) (SUM-OF-SQUARES 0))
        (MACROLET ((LOOP-FINISH NIL '(GO SYSTEM::END-LOOP)))
         (TAGBODY SYSTEM::BEGIN-LOOP (WHEN (ENDP #:LIST-8731) (LOOP-FINISH))
          (SETQ X (CAR #:LIST-8731))
          (PROGN (SETQ SUM-OF-SQUARES (+ SUM-OF-SQUARES (* X X)))
           (WHEN X (INCF N)))
          (PSETQ #:LIST-8731 (CDR #:LIST-8731)) (GO SYSTEM::BEGIN-LOOP)
          SYSTEM::END-LOOP
          (MACROLET
           ((LOOP-FINISH NIL (SYSTEM::LOOP-FINISH-WARN) '(GO SYSTEM::END-LOOP)))
           (PROGN (RETURN (SQRT (/ SUM-OF-SQUARES N))))))))))))) ;

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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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