Re: C++ comma operator ?

From	Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups	comp.lang.c++
Subject	Re: C++ comma operator ?
Date	2022-09-30 12:41 -0700
Organization	None to speak of
Message-ID	<871qrsmyyl.fsf@nosuchdomain.example.com> (permalink)
References	<th5sej$tqvo$1@dont-email.me>

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Lynn McGuire <lynnmcguire5@gmail.com> writes:
> Is this C++ statement using the comma operator ?
>
>       write(6, "(3(1x,i3),1x,f12.6,1x,f12.6)"), hkl(1, i), hkl(2, i),
>         hkl(3, i), f_calc(1, i), f_calc(2, i);

Yes, five of them, easily seen by reformatting the code:

    write(6, "(3(1x,i3),1x,f12.6,1x,f12.6)"),
    hkl(1, i),
    hkl(2, i),
    hkl(3, i),
    f_calc(1, i),
    f_calc(2, i);

Assuming there's no macro funny business going on, that's 6 function
calls (or macro invocations?) separated by comma operators.  (The commas
separating function arguments are of course not comma operators.)

Replacing the comma at the end of each line by a semicolon (and possibly
surrounding the whole thing with curly braces) yields equivalent code.
The braces are needed if the context is something like:

    if (condition)
        write(6, "(3(1x,i3),1x,f12.6,1x,f12.6)"), hkl(1, i), hkl(2, i),
        hkl(3, i), f_calc(1, i), f_calc(2, i);

Things might change if any of write, hkl, and f_calc is a macro.  If
they're well behaved macros, it shouldn't matter.

> There is a large open source template library supporting this
> statement from Fortran to C++ Fable software.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips
void Void(void) { Void(); } /* The recursive call of the void */

Thread

C++ comma operator ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-09-29 23:48 -0500
  Re: C++ comma operator ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-09-30 00:01 -0500
    Re: C++ comma operator ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-09-30 00:03 -0500
  Re: C++ comma operator ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-09-30 01:05 -0400
    Re: C++ comma operator ? red floyd <no.spam.here@its.invalid> - 2022-09-29 22:45 -0700
      Re: C++ comma operator ? scott@slp53.sl.home (Scott Lurndal) - 2022-09-30 15:16 +0000
        Re: C++ comma operator ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-09-30 13:53 -0500
          Re: C++ comma operator ? Gawr Gura <gawrgura@mail.hololive.com> - 2022-09-30 13:17 -0700
          Re: C++ comma operator ? scott@slp53.sl.home (Scott Lurndal) - 2022-10-01 16:56 +0000
            Re: C++ comma operator ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-01 13:13 -0500
            Re: C++ comma operator ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-10-03 02:32 -0700
              Re: C++ comma operator ? Juha Nieminen <nospam@thanks.invalid> - 2022-10-03 10:48 +0000
    Re: C++ comma operator ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-09-30 13:32 -0500
      Re: C++ comma operator ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-01 14:30 -0500
        Re: C++ comma operator ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-10-02 16:08 -0400
    Re: C++ comma operator ? Manfred <noname@add.invalid> - 2022-10-01 01:03 +0200
      Re: C++ comma operator ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-09-30 23:09 -0500
  Re: C++ comma operator ? Gawr Gura <gawrgura@mail.hololive.com> - 2022-09-29 23:19 -0700
    Re: C++ comma operator ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-09-30 13:31 -0500
  Re: C++ comma operator ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-30 12:41 -0700
    Re: C++ comma operator ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-10-03 02:38 -0700
  Re: C++ comma operator ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-09-30 23:48 -0500

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