[OT] My C++ talk at GoingNative 2013 (page 3)

On Thu, 19 Sep 2013 14:31:28 -0700, Walter Bright wrote: > On 9/18/2013 1:23 AM, Olivier Pisano wrote: >> On Friday, 13 September 2013 at 06:51:52 UTC, deadalnix wrote: >>> >>> There is 2 ask us anything. Can you tell us which one and approximately when ? >> >> Yes, the first one ( http://channel9.msdn.com/Events/GoingNative/2013/Interactive-Panel-Ask- Us-Anything >> ) around 01:14:20. > > Classic Andrei! :-) > > Should zoom in on that and make a gif! Yessir: http://imgur.com/W5AMy0P

On Thu, 19 Sep 2013 22:56:55 +0000, Justin Whear wrote: > On Thu, 19 Sep 2013 14:31:28 -0700, Walter Bright wrote: > >> On 9/18/2013 1:23 AM, Olivier Pisano wrote: >> >> Classic Andrei! :-) >> >> Should zoom in on that and make a gif! > > Yessir: http://imgur.com/W5AMy0P I think I'm going to start posting simply this in response to any statement that I find dubious.

On Friday, 20 September 2013 at 15:52:35 UTC, Justin Whear wrote: > On Thu, 19 Sep 2013 22:56:55 +0000, Justin Whear wrote: > >> On Thu, 19 Sep 2013 14:31:28 -0700, Walter Bright wrote: >> >>> On 9/18/2013 1:23 AM, Olivier Pisano wrote: >>> >>> Classic Andrei! :-) >>> >>> Should zoom in on that and make a gif! >> >> Yessir: http://imgur.com/W5AMy0P > > I think I'm going to start posting simply this in response to any > statement that I find dubious. It has quite some meme potential ^^

On 9/19/13 3:56 PM, Justin Whear wrote: > On Thu, 19 Sep 2013 14:31:28 -0700, Walter Bright wrote: > >> On 9/18/2013 1:23 AM, Olivier Pisano wrote: >>> On Friday, 13 September 2013 at 06:51:52 UTC, deadalnix wrote: >>>> >>>> There is 2 ask us anything. Can you tell us which one and >>>> approximately when ? >>> >>> Yes, the first one ( >>> http://channel9.msdn.com/Events/GoingNative/2013/Interactive-Panel-Ask- > Us-Anything >>> ) around 01:14:20. >> >> Classic Andrei! :-) >> >> Should zoom in on that and make a gif! > > Yessir: http://imgur.com/W5AMy0P Awesome. My coworkers added that to our panoply of visual comments in our review tool (Phabricator). Now any code reviewer could insert the word "skeptical" to insert that image in a review. Fits how I feel about some code, notably my own :o). Thanks! Andrei

On Friday, 20 September 2013 at 16:09:46 UTC, Tobias Pankrath wrote: > On Friday, 20 September 2013 at 15:52:35 UTC, Justin Whear wrote: >> On Thu, 19 Sep 2013 22:56:55 +0000, Justin Whear wrote: >> >>> On Thu, 19 Sep 2013 14:31:28 -0700, Walter Bright wrote: >>> >>>> On 9/18/2013 1:23 AM, Olivier Pisano wrote: >>>> >>>> Classic Andrei! :-) >>>> >>>> Should zoom in on that and make a gif! >>> >>> Yessir: http://imgur.com/W5AMy0P >> >> I think I'm going to start posting simply this in response to any >> statement that I find dubious. > > It has quite some meme potential ^^ Heh, when I loaded it imgur claimed that 2 MB gif had already been downloaded almost 150k times, using 250 GBs of bandwidth. I had no idea the D forums were so popular. ;) Then, I reloaded the imgur page again and it cut the stats by a factor of 100, still not bad. I'm guessing they aren't using D to calculate their stats.

On Fri, 20 Sep 2013 10:50:23 -0700 Andrei Alexandrescu <SeeWebsiteForEmail@erdani.org> wrote: > On 9/19/13 3:56 PM, Justin Whear wrote: > > > > Yessir: http://imgur.com/W5AMy0P > > Awesome. My coworkers added that to our panoply of visual comments in our review tool (Phabricator). > > Now any code reviewer could insert the word "skeptical" to insert that image in a review. Fits how I feel about some code, notably my own :o). > That's just awesome :)

September 22, 2013

Re: [OT] My C++ talk at GoingNative 2013

Posted by Ali Çehreli
in reply to Andrei Alexandrescu

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Ali Çehreli

Posted in reply to Andrei Alexandrescu

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On 09/09/2013 09:43 AM, Andrei Alexandrescu wrote:
> http://www.reddit.com/r/programming/comments/1m1izv/goingnative_2013_writing_quick_code_in_c_quickly/
>
>
> Andrei

Great talk indeed!

I am late to the party so instead of commenting on Reddit I will write here.

There are two points made in the talk that favor out parameters over return-by-value:

<quote>
Slide 33/40:

The Composability Argument

* Appending to containers: cheap

* Concatenating containers: expensive

Slide 34/40

The Measurements Argument

* Which one is faster?

// API 1: Returns next line (with terminator)
// or empty string at end of file
string nextLine(istream&);

// API 2: Fills string with next line (with terminator)
// returns false at end of file
bool nextLine(istream&, string& s);
</quote>

This topic happens to be one of my favorite interview questions. :)

If program correctness is valued, the by-ref out parameter may not be the faster option because the caller may not want to pass in a precious container to a function only to be halfway appended to it.

Imagine that the function appends N/2 items to the caller's container and then throws. If that half-baked state is not desired, either the function itself or the caller may have to undo what has already been appended.

If the function should not append but first clear the container and then create it anew, then fair enough, we would be taking advantage of already-allocated buffer of the container. (A valid consideration for arrays but not every pointer-based data structure takes advantage of old buffers.) But still, for correctness, the function should not append but create anew (on top of the existing buffer), which necessitates "concatenation" on the caller side anyway.

Ali

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