DIP 1027---String Interpolation---Format Assessment

[Arine]

On Thursday, 27 February 2020 at 18:58:40 UTC, Walter Bright 
wrote:
> On 2/27/2020 1:45 AM, Rainer Schuetze wrote:
>> The string buffer could also be stack allocated or manually 
>> managed with
>> malloc/free by the string interpolation type.
>
> It's quite a big deal to make that work, and does not address 
> the inherent inefficiency of it.
>
> printf, for all its faults, is very efficient, and one reason 
> is it does not require arbitrary temporary storage. Another is 
> it does not require exception handlers. I, for one, simply 
> would not use such when printf is available.

It isn't that efficient. There are a lot of implementations 
faster than it, and funnily enough they allocate memory, use 
exceptions, and RAII.

> People often overlook how *expensive* RAII is. Turn exception 
> handling on and have a look at the generated code.

There was a whole other thread about this, and people found the 
assembly generated isn't all that different. Yes throwing 
exceptions is expensive, but what you are talking about, the cost 
of not throwing them, it really isn't. You are making it out to 
be a bigger problem than it actually is. If it caused such a huge 
performance hit, then exceptions simply wouldn't be used at all 
in C++. But that's not the case.

> It's a minor syntactic convenience with an unexpected large and 
> hidden cost. That's not what D is about.
>
> Leave this at the user's discretion with:
>
>     f(format("hello %betty"));
>
> where the user chooses via the format function which method of 
> handling temporaries he finds appropriate.

There are quite a few places that D has large hidden costs. Hell 
GC and any feature or otherwise that uses it is a large and 
hidden cost. You can't really say D is not about unexpected large 
and hidden costs when it has a GC integrated into quite a few 
features that make it invisible.