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Re: C++20 concepts rocks

From Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups comp.lang.c++
Subject Re: C++20 concepts rocks
Date 2022-02-04 23:53 -0800
Organization A noiseless patient Spider
Message-ID <865yptlpgf.fsf@linuxsc.com> (permalink)
References <stj7m4$bim$1@dont-email.me> <stjd0m$1380$1@gioia.aioe.org> <stjdbe$7th$1@dont-email.me> <87k0easj5d.fsf@bsb.me.uk>

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Ben Bacarisse <ben.usenet@bsb.me.uk> writes:

> Bonita Montero <Bonita.Montero@gmail.com> writes:
>
>> Am 04.02.2022 um 15:25 schrieb Muttley@dastardlyhq.com:
>>
>>> On Fri, 4 Feb 2022 13:54:27 +0100
>>> Bonita Montero <Bonita.Montero@gmail.com> wrote:
>>>
>>>> I've just written a small routine:
>>>>
>>>> [.. some c++ code ..]
>>>
>>> Thats nice.  Personally I'd just use printf().
>>
>> You can't do what I did with (s)printf().
>
> template<typename StringType>
> requires is_same_v<StringType,
>                    basic_string<typename StringType::value_type,
>                                 typename StringType::traits_type,
>                                 typename StringType::allocator_type>>
> StringType formatClockCycles(uint64_t clockCycles)
> {
>    char result[28], *ep = (&result)[1];
>    do {
>       sprintf(ep - 4, "%03lu", clockCycles % 1000);
>       if (ep != (&result)[1]) ep[-1] = '.';
>       ep -= 4;
>    } while (clockCycles /= 1000);
>    while (*ep == '0' && ep[1]) ep++;
>    return ep;
> }
>
> (the appropriate comment on the 28 is left as an exercise to the reader!)

Most of the work can be done using only a single call to sprintf().
(Disclaimer:  not compiled.)


    template< typename StringType >
        requires
            is_same_v<
                StringType,
                basic_string<
                    typename StringType::value_type,
                    typename StringType::traits_type,
                    typename StringType::allocator_type
                >
            >
    StringType
    formatClockCycles( uint64_t clockCycles ){
        char result[ 27 ];
        int n = sprintf( result, "%" PRIu64, clockCycles );
        char *ep = (&result)[1];

        *--ep = 0;
        while(  n > 3  ){
            memmove( ep -= 3, &result[ n -= 3 ], 3 );
            *--ep = '.';
        }
        do  *--ep = result[ --n ];  while(  n > 0  );

        return  ep;
    }

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Thread

C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-04 13:54 +0100
  Re: C++20 concepts rocks Muttley@dastardlyhq.com - 2022-02-04 14:25 +0000
    Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-04 15:31 +0100
      Re: C++20 concepts rocks Muttley@dastardlyhq.com - 2022-02-04 14:54 +0000
        Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-04 17:41 +0100
          Re: C++20 concepts rocks Muttley@dastardlyhq.com - 2022-02-05 11:31 +0000
            Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-05 12:49 +0100
              Re: C++20 concepts rocks Muttley@dastardlyhq.com - 2022-02-05 12:20 +0000
      Re: C++20 concepts rocks Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-02-04 16:15 +0000
        Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-04 17:43 +0100
        Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-05 01:51 +0100
          Re: C++20 concepts rocks Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-02-05 01:59 +0000
          Re: C++20 concepts rocks James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-02-04 23:05 -0500
            Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-05 11:56 +0100
              Re: C++20 concepts rocks David Brown <david.brown@hesbynett.no> - 2022-02-05 13:53 +0100
                Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-05 14:12 +0100
                Re: C++20 concepts rocks Anand Hariharan <mailto.anand.hariharan@gmail.com> - 2022-02-12 11:13 -0800
                Re: C++20 concepts rocks James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-02-12 22:18 -0500
                Re: C++20 concepts rocks Richard Damon <Richard@Damon-Family.org> - 2022-02-13 12:51 -0500
                Re: C++20 concepts rocks Paavo Helde <eesnimi@osa.pri.ee> - 2022-02-13 20:16 +0200
                Re: C++20 concepts rocks James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-02-13 14:12 -0500
                Re: C++20 concepts rocks Richard Damon <Richard@Damon-Family.org> - 2022-02-13 16:22 -0500
                Re: C++20 concepts rocks James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-02-13 17:18 -0500
                Re: C++20 concepts rocks Öö Tiib <ootiib@hot.ee> - 2022-02-14 00:51 -0800
                Re: C++20 concepts rocks "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-02-14 08:29 -0800
          Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-04 23:37 -0800
            Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-05 11:58 +0100
              Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-06 02:16 -0800
            Re: C++20 concepts rocks "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-02-05 12:35 -0800
              Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-06 05:54 -0800
              Re: C++20 concepts rocks Manfred <noname@add.invalid> - 2022-02-06 19:43 +0100
        Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-04 23:53 -0800
          Re: C++20 concepts rocks red floyd <no.spam.here@its.invalid> - 2022-02-05 10:10 -0800
            Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-05 19:51 +0100
              Re: C++20 concepts rocks red floyd <no.spam.here@its.invalid> - 2022-02-05 16:42 -0800
                Re: C++20 concepts rocks Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-02-06 01:39 +0000
                Re: C++20 concepts rocks red floyd <no.spam.here@its.invalid> - 2022-02-05 18:02 -0800
                Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-06 09:57 +0100
                Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-06 10:57 +0100
                Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-06 12:40 +0100
                Re: C++20 concepts rocks Öö Tiib <ootiib@hot.ee> - 2022-02-06 03:53 -0800
                Re: C++20 concepts rocks Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-02-06 14:35 +0000
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-06 11:20 -0800
                Re: C++20 concepts rocks Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-02-06 21:53 +0000
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-06 19:03 -0800
                Re: C++20 concepts rocks Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-02-07 11:50 +0000
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-07 06:26 -0800
                Re: C++20 concepts rocks Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-02-07 15:48 +0000
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-07 12:16 -0800
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-07 22:27 -0800
                Re: C++20 concepts rocks Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-02-09 21:43 +0000
                Re: C++20 concepts rocks James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-02-09 21:07 -0500
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-09 21:25 -0800
                Re: C++20 concepts rocks Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-02-10 13:05 +0000
                Re: C++20 concepts rocks James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-02-10 11:19 -0500
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-11 05:41 -0800
                Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-11 17:06 +0100
                Re: C++20 concepts rocks James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-02-11 11:50 -0500
                Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-11 21:13 +0100
                Re: C++20 concepts rocks scott@slp53.sl.home (Scott Lurndal) - 2022-02-11 17:06 +0000
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-15 00:10 -0800
                Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-15 20:58 +0100
                Re: C++20 concepts rocks Juha Nieminen <nospam@thanks.invalid> - 2022-02-16 06:40 +0000
                Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-16 09:54 +0100
                Re: C++20 concepts rocks Muttley@dastardlyhq.com - 2022-02-16 09:00 +0000
                Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-16 20:25 +0100
                Re: C++20 concepts rocks Muttley@dastardlyhq.com - 2022-02-17 08:53 +0000
                Re: C++20 concepts rocks Paavo Helde <eesnimi@osa.pri.ee> - 2022-02-17 16:11 +0200
                Re: C++20 concepts rocks James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-02-17 10:58 -0500
                Re: C++20 concepts rocks Juha Nieminen <nospam@thanks.invalid> - 2022-02-17 07:32 +0000
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-04-19 02:21 -0700
                Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-04-19 11:56 +0200
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-04-25 03:02 -0700
                Re: C++20 concepts rocks Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-02-12 00:01 +0000
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-14 23:55 -0800
                Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-07 18:31 +0100
                Re: C++20 concepts rocks scott@slp53.sl.home (Scott Lurndal) - 2022-02-07 17:43 +0000
                Re: C++20 concepts rocks James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-02-06 14:25 -0500
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-06 02:01 -0800
                Re: C++20 concepts rocks red floyd <no.spam.here@its.invalid> - 2022-02-06 19:37 -0800
                Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-07 10:18 +0100
                Re: C++20 concepts rocks Paavo Helde <eesnimi@osa.pri.ee> - 2022-02-07 11:32 +0200
                Re: C++20 concepts rocks red floyd <no.spam.here@its.invalid> - 2022-02-07 07:55 -0800
            Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-06 02:11 -0800
              Re: C++20 concepts rocks "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-02-06 13:13 +0100
                Re: C++20 concepts rocks Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-06 04:58 -0800
                Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-06 14:08 +0100
        Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-05 12:48 +0100
    Re: C++20 concepts rocks Juha Nieminen <nospam@thanks.invalid> - 2022-02-04 20:15 +0000
      Re: C++20 concepts rocks Muttley@dastardlyhq.com - 2022-02-05 11:32 +0000
        Re: C++20 concepts rocks Juha Nieminen <nospam@thanks.invalid> - 2022-02-06 08:28 +0000
          Re: C++20 concepts rocks Muttley@dastardlyhq.com - 2022-02-07 09:52 +0000
            Re: C++20 concepts rocks Juha Nieminen <nospam@thanks.invalid> - 2022-02-08 07:05 +0000
              Re: C++20 concepts rocks Muttley@dastardlyhq.com - 2022-02-08 09:25 +0000
                Re: C++20 concepts rocks Juha Nieminen <nospam@thanks.invalid> - 2022-02-08 10:09 +0000
  Re: C++20 concepts rocks Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-02-04 12:10 -0800
    Re: C++20 concepts rocks Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-05 13:41 +0100
      Re: C++20 concepts rocks "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-02-05 19:28 -0800
  A little benchmark: Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-05 13:22 +0100
    A better benchmark Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-06 14:56 +0100
      A improved routine Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-07 15:19 +0100
      Re: A better benchmark Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-07 06:57 -0800
        Re: A better benchmark Bonita Montero <Bonita.Montero@gmail.com> - 2022-02-07 18:30 +0100

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