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

Subject: Re: [boost] Variadic append for std::string
From: Olaf van der Spek (ml_at_[hidden])
Date: 2017-01-03 10:08:18

On Tue, Jan 3, 2017 at 3:48 PM, Christof Donat <cd_at_[hidden]> wrote:
> Hi,
>
> Am 03.01.2017 15:23, schrieb Olaf van der Spek:
>>
>> On Tue, Jan 3, 2017 at 3:16 PM, Christof Donat <cd_at_[hidden]> wrote:
>> The extra parentheses and the .str() part are annoying.. same goes for
>> boost::format.
>
>
> I see. For me that is not a big issue, but people are different.

I think the language still doesn't allow temporaries to bind to
mutable& so we might've cheered too soon.. :(

>> How about this one?
>>
>> throw std::runtime_error("Error "s << 47);
>
>
> Uh. How does that work with
>
>   std::cout << "Error "s << 47;
>
> Will that be
>
>   (std::cout << "Error "s) << 47;
>
> or
>
>   std::cout << ("Error "s << 47);

We've got rules for that..
http://en.cppreference.com/w/cpp/language/operator_precedence

> Also I'd expect a std::string to behave like a stream then and try to
> use e.g. manipulators. Maybe that would be acceptable with a different
> operator. e.g. like in SQL:
>
>  throw std::runtime_error("Error "s || 47);
>
> Now this is explicit:
>
>   std::cout << "Error "s || 47; // versus

Why would you want to combine << for ostream and string? Just use the
ostream one in both cases.

I think << is quite elegant.

-- 
Olaf