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Re: What is the good of new way of coding?

From "Alf P. Steinbach" <alf.p.steinbach@gmail.com>
Newsgroups comp.lang.c++
Subject Re: What is the good of new way of coding?
Date 2022-09-17 19:55 +0200
Organization A noiseless patient Spider
Message-ID <tg51mc$7cfq$1@dont-email.me> (permalink)
References (3 earlier) <tg4p7j$6kku$1@dont-email.me> <tg4qtf$1ub0$1@gioia.aioe.org> <tg4r45$6q5f$1@dont-email.me> <tg4rnu$aeq$1@gioia.aioe.org> <tg4sug$6vcn$1@dont-email.me>

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On 17 Sept 2022 18:34, Bonita Montero wrote:
> Am 17.09.2022 um 18:13 schrieb Muttley@dastardlyhq.com:
>> On Sat, 17 Sep 2022 18:03:37 +0200
>> Bonita Montero <Bonita.Montero@gmail.com> wrote:
>>> Am 17.09.2022 um 17:59 schrieb Muttley@dastardlyhq.com:
>>>> On Sat, 17 Sep 2022 17:31:19 +0200
>>>> Bonita Montero <Bonita.Montero@gmail.com> wrote:
>>>>> Am 17.09.2022 um 16:50 schrieb Muttley@dastardlyhq.com:
>>>>>> On Sat, 17 Sep 2022 15:03:25 +0200
>>>>>> Bonita Montero <Bonita.Montero@gmail.com> wrote:
>>>>>>> Am 17.09.2022 um 14:46 schrieb wij:
>>>>>>>> I did not update my C++ understanding (probable since C++11) to 
>>>>>>>> find out
>>> I
>>>>>>>> cannot understand what the codes are about !!!
>>>>>>>>
>>>>>>>> --- frorm https://groups.google.com/g/comp.lang.c++/c/2ebc6ifoPr4
>>>>>>>> #include <iostream>
>>>>>>>> #include <utility>
>>>>>>>>
>>>>>>>> using namespace std;
>>>>>>>>
>>>>>>>> int main()
>>>>>>>> {
>>>>>>>> auto pow = []<unsigned P>( double b, integral_constant<unsigned, 
>>>>>>>> P> )
>>>>>>>> -> double
>>>>>>>> {
>>>>>>>> auto unroll = [&]<size_t ... Indices>( index_sequence<Indices 
>>>>>>>> ...> )
>>>>>>>> -> double
>>>>>>>> {
>>>>>>>> return ((Indices, b) * ...);
>>>>>>>> };
>>>>>>>> if constexpr( P )
>>>>>>>> return unroll( make_index_sequence<P>() );
>>>>>>>> else
>>>>>>>> return b;
>>>>>>>> };
>>>>>>>> cout << pow( 2.0, integral_constant<unsigned, 10'000>() ) << endl;
>>>>>>>> }
>>>>>>>> ------
>>>>>>>>
>>>>>>>> Question1: What would the code look like if using C++2006 for 
>>>>>>>> the above
>>>>>>> 'program'?
>>>>>>>
>>>>>>> It's not possible to write that before C++20.
>>>>>>
>>>>>> Really? So it outputs some special assembler reserved for C++20 
>>>>>> does it?
>>>>>>
>>>>>
>>>>> No, you can't unroll variable.
>>>>
>>>> I'm pretty sure the same functionality could be achieved in older 
>>>> C++ or
>>>> even C albeit with more lines of code.
>>>>
>>>
>>> Show me.
>>>
>>
>> I don't have a c++ 20 compiler so I can't see what it does and I have 
>> better
>> things to do on a saturday than run it in my head.
>>
> 
> Without C++20 you would have to unroll the fold expressions
> N times, in this case 10.000 times. Have fun !

The Boost preprocessor library comes to mind.


- Alf

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Thread

What is the good of new way of coding? wij <wyniijj2@gmail.com> - 2022-09-17 05:46 -0700
  Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-17 15:03 +0200
    Re: What is the good of new way of coding? Muttley@dastardlyhq.com - 2022-09-17 14:50 +0000
      Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-17 17:31 +0200
        Re: What is the good of new way of coding? Muttley@dastardlyhq.com - 2022-09-17 15:59 +0000
          Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-17 18:03 +0200
            Re: What is the good of new way of coding? Muttley@dastardlyhq.com - 2022-09-17 16:13 +0000
              Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-17 18:34 +0200
                Re: What is the good of new way of coding? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-09-17 19:55 +0200
                Re: What is the good of new way of coding? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-09-17 12:03 -0700
                Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-18 16:21 +0200
                Re: What is the good of new way of coding? Muttley@dastardlyhq.com - 2022-09-19 08:30 +0000
                Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-19 10:37 +0200
                Re: What is the good of new way of coding? Muttley@dastardlyhq.com - 2022-09-19 08:54 +0000
                Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-19 11:13 +0200
  Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-17 15:23 +0200
    Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-17 15:38 +0200
  Re: What is the good of new way of coding? Andreas Kempe <kempe@lysator.liu.se> - 2022-09-17 14:37 +0000
    Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-17 16:40 +0200
      Re: What is the good of new way of coding? Andreas Kempe <kempe@lysator.liu.se> - 2022-09-17 20:52 +0000
        Re: What is the good of new way of coding? Mr Flibble <flibble@reddwarf.jmc.corp> - 2022-09-17 22:18 +0100
          Re: What is the good of new way of coding? Mr Flibble <flibble@reddwarf.jmc.corp> - 2022-09-17 22:21 +0100
            Re: What is the good of new way of coding? Andreas Kempe <kempe@lysator.liu.se> - 2022-09-17 21:31 +0000
  Re: What is the good of new way of coding? Muttley@dastardlyhq.com - 2022-09-17 14:52 +0000
    Re: What is the good of new way of coding? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-17 17:32 +0200

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