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Groups > comp.lang.c++ > #82899
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| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
| Newsgroups | comp.lang.c++ |
| Subject | Re: C++20 concepts rocks |
| Date | Fri, 04 Feb 2022 16:15:10 +0000 |
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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:
>>>
>>> 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 )
>> Some C++ prototypes are almost comical they're so unreadable.
>
> For those who are familiar with concepts that's readable.
>
>>> using dig_arr_t = array<uint8_t, 20>; // max 20 digits for 64 bit
>>> using dig_arr_it = dig_arr_t::iterator;
>>> dig_arr_t reverseDigits;
>>> dig_arr_it rDigitsEnd = reverseDigits.begin();
>>> do
>>> *rDigitsEnd++ = clockCycles % 10,
>>> clockCycles /= 10;
>>> while( clockCycles );
>>> size_t
>>> digitsLen = rDigitsEnd - reverseDigits.begin(),
>>> groups = (digitsLen - 1) / 3;
>>> StringType str( digitsLen + groups, '\0' );
>>> typename StringType::iterator wrt = str.end();
>>> dig_arr_it digit = reverseDigits.begin();
>>> for( dig_arr_it groupsEnd = reverseDigits.begin() + groups * 3; digit
>>> != groupsEnd; wrt -= 4, digit += 3 )
>>> wrt[-1] = digit[0] + '0',
>>> wrt[-2] = digit[1] + '0',
>>> wrt[-3] = digit[2] + '0',
>>> wrt[-4] = '.';
>>> do
>>> *--wrt = *digit++ + '0';
>>> while( digit != rDigitsEnd );
>>> return str;
>>> }
>>>
>>> The cool thing here that the concept above doesn't have an error if
>>> ....::value_type, ...::traits_type and ...::allocator_type are missing;
>>> I just get an error as if I'd also included a check for the existence
>>> of these types.
>> 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!)
--
Ben.
Back to comp.lang.c++ | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll 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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