Re: [boost] Variadic append for std::string

Subject: Re: [boost] Variadic append for std::string
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2017-01-03 09:53:56

On 01/03/17 17:23, Olaf van der Spek wrote:
> On Tue, Jan 3, 2017 at 3:16 PM, Christof Donat <cd_at_[hidden]> wrote:
>> Hin
>>
>> Am 03.01.2017 14:20, schrieb Olaf van der Spek:
>>>
>>> On Tue, Jan 3, 2017 at 2:19 PM, Christof Donat <cd_at_[hidden]> wrote:
>>>>
>>>> Am 01.01.2017 00:21, schrieb Andrey Semashev:
>>>>>
>>>>>
>>>>>   throw std::runtime_error(format(std::string()) << "Error " << 47);
>>>>
>>>>
>>>>
>>>> How would that differ from
>>>>
>>>>   throw std::runtime_error((std::ostringstream{} << "Error " <<
>>>> 47).str());
>>>
>>>
>>> Simpler syntax, better performance
>>
>>
>> I see the chances for better performance, but for the syntax I don't really
>> see
>> any remarkable improvements.
>
> The extra parentheses and the .str() part are annoying.. same goes for
> boost::format.
>
> How about this one?
>
> throw std::runtime_error("Error "s << 47);

Well, if we're using UDLs, we might as well use my `format` proposal or 
a stream or Boost.Format behind the scene.

   throw std::runtime_error("Error "fmt << 47);
   throw std::runtime_error("Error "strm << 47);
   throw std::runtime_error("Error %d"fmt % 47);

Each of the UDL operators would create a wrapper that implements 
formatting and is convertible to std::string. No need to infect 
std::string itself with formatting.