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

Subject: Re: [boost] Variadic append for std::string
From: Christof Donat (cd_at_[hidden])
Date: 2017-01-16 04:57:21

Am 16.01.2017 09:54, schrieb Olaf van der Spek:
> On Sun, Jan 15, 2017 at 9:42 PM, Damien Buhl <damien.buhl_at_[hidden]> 
> wrote:
> 
>> On 15/01/2017 14:39, Christof Donat wrote:
>> > Libraries like boost::format have their strengths, when simply
>> > concatenating information does not fit the needs. E.g. for
>> > internationalized text output. I like boost::format a lot, but speed
>> > actually is not its focus.
>> I personally uses boost::format alot, but I think boost::format would 
>> be
>> easier and shorter to use if it would be callable with an `std::string
>> snprintf(format_str, args...)`. And it would be awesome that 
>> format_str
>> would be, if already known at compile time handled with Metaparse.
>> Sorry for getting off-topic. :D
>> 
> 
> Can't boost::format be updated to a variadic variant?

I think so. Something like this should be possible, of course:

auto format_args_imp(const boost::format& f) -> const boost::format& {
     return f;
}

template<typename Arg1, typename ... Args>
auto format_args_imp(const boost::format& f, Arg1 arg1, Args ... args) 
-> const boost::format& {
     return format_args_impl(f % arg1, args...);
}

template<typename ... Args>
auto format_args(const std::string& f, Args...args) -> std::string {
     return format_args_impl(f, args...).str();
}

// ...
auto first_which = format_args("When shall we %1% meet again? In %2%, 
%3%, or in %4%?"s, 3, "thunder"s, "lightning"s, "rain"s);

I have not tried to compile this, so please just take it as a sketch. It 
inherits most of the advantages and disadvantages of boost::format, of 
course.

Christof