Re: 'Amalgamated' source code

Newsgroups	comp.lang.c
Date	2017-01-05 10:11 -0800
References	(11 earlier) <c901fe2c-600f-430c-be7c-3bfc274e06e3@googlegroups.com> <8b7b2773-2a60-44c5-a9f4-e5fa23eff966@googlegroups.com> <87bmvlk2cr.fsf@bsb.me.uk> <a7f547cf-ab84-4610-9607-ae4eaec7b152@googlegroups.com> <871swhjv3q.fsf@bsb.me.uk>
Message-ID	<2f8a7a13-ba5a-46da-b9a5-eb84223d00a7@googlegroups.com> (permalink)
Subject	Re: 'Amalgamated' source code
From	supercat@casperkitty.com

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On Thursday, January 5, 2017 at 11:05:23 AM UTC-6, Ben Bacarisse wrote:
> supercat writes:
> <snip>
> > How could a compiler avoid having to either use different expansion logic
> > in cases where a macro is used as an operand to # versus cases where it
> > isn't,
> 
> The pre-processor should follow the specified algorithm.  The fact that
> you refer to "a macro" bring an operand to # suggests you haven't
> studied that algorithm.  The operand of # is a parameter name and the
> corresponding argument sequence (a list of token) is never expanded
> before being turned into a string.

Within the asString2 macro (the one that uses #), it acts upon the named
parameter x, but the purpose of that macro is to apply the operator to
the argument; the example code uses that macro twice, and in each case it
is applied to the expansion of another macro.  The expansions of both of
the macros to which it is applied have identical string representations
(i.e. +++++) but one behaves like ++ + ++ and the other behaves like
++ + + +.  Given the difference between the string representation that
would be needed for #, and the way in which the tokens would need to be
output for downstream processing, I would think keeping track of string
representations with and without the added spaces would be a reasonable
way to handle that (to get the string representation of two tokens that
appear without whitespace or are explicitly pasted, simply concatenate
their string representations; for the semantic form, either concatenate
the semantic forms with a whitespace between them (for consecutive
placement without a pasting operator) or with any whitespace between
them suppressed (when using the ## pasting operator).

While keeping track of both string forms would hardly be the only way to
handle things, it doesn't seem like an unreasonable one.  An alternative
would be to define an "invisible whitespace" character which will not get
included in strings generated by the # operator, but will get replaced
with whitespace in unquoted preprocessor output.

Thread

'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-03 15:14 +0000
  Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-03 08:47 -0800
    Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-03 19:47 +0000
      Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-03 12:48 -0800
        Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-03 21:36 +0000
          Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-03 16:01 -0800
            Re: 'Amalgamated' source code Keith Thompson <kst-u@mib.org> - 2017-01-03 16:26 -0800
              Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-03 18:00 -0800
                Re: 'Amalgamated' source code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-04 03:34 +0000
                Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-04 03:31 -0800
                Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-04 12:03 +0000
                Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-04 05:00 -0800
                Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-05 02:38 -0800
                Re: 'Amalgamated' source code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-05 14:28 +0000
                Re: 'Amalgamated' source code supercat@casperkitty.com - 2017-01-05 08:20 -0800
                Re: 'Amalgamated' source code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-05 17:05 +0000
                Re: 'Amalgamated' source code supercat@casperkitty.com - 2017-01-05 10:11 -0800
                Re: 'Amalgamated' source code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-05 19:46 +0000
                Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-05 12:15 -0800
                Re: 'Amalgamated' source code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-05 21:54 +0000
                Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-05 17:40 +0000
                Re: 'Amalgamated' source code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-05 19:33 +0000
            Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-04 10:53 +0000
          Re: 'Amalgamated' source code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-04 01:51 +0000
        Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-04 11:54 +0000
          Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-04 05:57 -0800
            Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-04 14:20 +0000
            Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-04 15:07 +0000
              Re: 'Amalgamated' source code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-04 15:34 +0000
                Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-04 08:03 -0800
                Re: 'Amalgamated' source code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-04 17:09 +0000
                Re: 'Amalgamated' source code bart4858@gmail.com - 2017-01-04 08:54 -0800
                Re: 'Amalgamated' source code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-04 17:22 +0000
              Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-04 07:55 -0800
                Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-05 18:04 +0000
                Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-01-05 11:50 -0800
  Re: 'Amalgamated' source code Jorgen Grahn <grahn+nntp@snipabacken.se> - 2017-01-04 16:29 +0000
    Re: 'Amalgamated' source code bart4858@gmail.com - 2017-01-04 09:15 -0800
      Re: 'Amalgamated' source code Ian Collins <ian-news@hotmail.com> - 2017-01-05 08:33 +1300
        Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-04 20:26 +0000
          Re: 'Amalgamated' source code supercat@casperkitty.com - 2017-01-04 13:09 -0800
          Re: 'Amalgamated' source code Ian Collins <ian-news@hotmail.com> - 2017-01-05 10:21 +1300
            Re: 'Amalgamated' source code supercat@casperkitty.com - 2017-01-04 13:51 -0800
            Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-04 22:02 +0000
              Re: 'Amalgamated' source code Ian Collins <ian-news@hotmail.com> - 2017-01-05 11:15 +1300
      Re: 'Amalgamated' source code Jorgen Grahn <grahn+nntp@snipabacken.se> - 2017-01-07 06:38 +0000
        Re: 'Amalgamated' source code BartC <bc@freeuk.com> - 2017-01-07 11:35 +0000
    Re: 'Amalgamated' source code supercat@casperkitty.com - 2017-01-04 09:53 -0800
    Re: 'Amalgamated' source code Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-01-04 11:50 -0800
    Re: 'Amalgamated' source code raltbos@xs4all.nl (Richard Bos) - 2017-01-10 01:34 +0000
      Re: 'Amalgamated' source code Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-01-10 01:59 -0800
      Re: 'Amalgamated' source code Les Cargill <lcargill99@comcast.com> - 2017-01-10 06:55 -0600
      Re: 'Amalgamated' source code Richard Heathfield <rjh@cpax.org.uk> - 2017-01-10 14:48 +0000
  Re: 'Amalgamated' source code Thiago Adams <thiago.adams@gmail.com> - 2017-04-26 07:17 -0700

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