220 30017 <172d08f0-a3da-4b9e-bfdd-985fb1f527c8@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: join/split for string & string_view Date: Sun, 25 Dec 2016 07:41:44 -0800 (PST) Lines: 227 Approved: news@gmane.org Message-ID: <172d08f0-a3da-4b9e-bfdd-985fb1f527c8@isocpp.org> References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_687_533956310.1482680504223" X-Trace: blaine.gmane.org 1482680513 17993 195.159.176.226 (25 Dec 2016 15:41:53 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 25 Dec 2016 15:41:53 +0000 (UTC) Cc: lnaltidev@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBOOR77BAKGQEBL3JFMI@isocpp.org Sun Dec 25 16:41:49 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f72.google.com ([74.125.83.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cLAvd-00033K-JW for gclcip-std-proposals@m.gmane.org; Sun, 25 Dec 2016 16:41:41 +0100 Original-Received: by mail-pg0-f72.google.com with SMTP id u5sf247498187pgi.7 for ; Sun, 25 Dec 2016 07:41:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=lfswKkVx28gRDh6DJecMB7kl5RZcay8r3Q1Cb8wLsAo=; b=YzblX6DejUQoXVf/WFVXSw0C6WdGaNqVx7TghIGMyQTRpiUzUF5NH6SKmYauYavcDm XBoAcPOAr7ntrg9OObXZdkI0CSTUfPKKLH4cb9a46z06cNoq1ducG+8i9Shq1gPaiWWY 9VHkwQyzWS9P67YdFHq+j4Uk8mLfPcVzR3sHdb9FvTSFEvnGWIvffWbSHXSpoHC8oEae x+wSi0qTAxgqN2ECTh77ZX7d4rF8C8ZD/SuZp9SJ/A84tEAj8zmaKwjioMnqImv64MM7 TSX1mFuQPfQZPtqvRJhxWwXF4VHo5ZL9Go6Ph39yaFMUmnynojGPSkWwL7SrpXYCyRSe 6PBA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=lfswKkVx28gRDh6DJecMB7kl5RZcay8r3Q1Cb8wLsAo=; b=WPZvYpe06LOC8t8o+PuWUwI7EXDY80f+gyxk+g81p/0Cfok3NQXrnAkJ9Ug2HYU0/S 2kYUxQxPn01ppJ8X/2P/J64xhjscBkVYUAQ6KR4DqacNwiZSFr25eRFHjfFil87/C3u2 DPnuimiU2paogdEU+Pe5bp8CZ/ia1ow2qgb89jq1JkFRhi3md49GAxfFe9t6NKoH/Q/N iaAeL9jNVBjyvcXdUjiaFnMvpRJAvLlHODyUPSLiVVM3I2NnkOnnLZA9x7KkyYzYxmxk aFJOxvhuwNgE/FIvoO3svwkmOrwIPkmwzaAVIDe7evkgZbViuXBuMmIwOfqsUwB+X7EC 9dEQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version:x-original-sender:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=lfswKkVx28gRDh6DJecMB7kl5RZcay8r3Q1Cb8wLsAo=; b=bvHXzpDMFbPHOlmoeD3oaPO9PV0/BSyQjqRp4u2NwbxIiFjXWtM4O5AM1IWnMl3sxr c2hPfx/FGFn/VtswWbiYcAQqk+e3a3nCXHEZVVzTpUunk2BQCGmlSvSNDP8a1mruF9jn Esha1i7EvEMb1/3/BcakmHGbupxfYPecvQVFvUyMQFgg+MmQNB7TmvSEcSYCqo8DQ09z nS6y/hWje7Gc7ivg9Ulodn6MshOjA6eN8129jqgO298V2RnDXJ847tiIGQQWmlcg63NL W2EaHWfXVr9M8FTxpjBLTXymV+mp4rgLVqImb8x8YGt82d7sd5NQVChJcsZgP242YJ9z x1lg== X-Gm-Message-State: AIkVDXIiBPZyLoRXBk6a9+2zgDwSBZyVxMklz1ZOQLszsHtKVs1ITjLXqHhSXQJMgyN/0g== X-Received: by 10.99.2.70 with SMTP id 67mr13688796pgc.42.1482680505843; Sun, 25 Dec 2016 07:41:45 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.45.195 with SMTP id g61ls24584524otb.37.gmail; Sun, 25 Dec 2016 07:41:45 -0800 (PST) X-Received: by 10.157.51.88 with SMTP id u24mr345571otd.6.1482680504982; Sun, 25 Dec 2016 07:41:44 -0800 (PST) In-Reply-To: X-Original-Sender: jmckesson@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:30017 Archived-At: ------=_Part_687_533956310.1482680504223 Content-Type: multipart/alternative; boundary="----=_Part_688_969289153.1482680504224" ------=_Part_688_969289153.1482680504224 Content-Type: text/plain; charset=UTF-8 On Sunday, December 25, 2016 at 5:32:44 AM UTC-5, lnal...@gmail.com wrote: > > Hello, > > > Most of modern language (D, Python, Java, C#, Go, Rust) got a split method > on their string type, so I think it really make sense to have something > similar in C++. > All of those languages also only have a single string type. C++ has *hundreds*. Even the *standard library* has 2, and that doens't even count `const char*`. Having a `split` function that can *only* be used with the standard library string types is pathetic. Especially when it could be made to be used with any string type (that provides a conversion to `string_view`) with ease. If you want to suggest that `basic_string` and `string_view` should have member versions that call the non-member algorithms, fine. But the non-member function is where the actual work happens. > All of them returns a 'vector' and I think is the main waited result. > No. While we should not be ignorant of what other languages are doing, we also should not pretend that the design of other languages is a priori correct for C++. We should do what is best for C++. And one principle of C++ is that we do not make people pay for features they don't need to use. Forcing the return of a `vector` makes people pay for memory allocations that they may not use. I think it should not be required to mastering all subtilities of the STL > to do something a simple as that. > Master the subtleties of what? Of using a range? That should be an early lesson for C++ programmers; it's hardly deep metaprogramming magic. If you're going to be able to work in a language, you *need* to know its idioms. And ranges are very important idioms in C++. We shouldn't cater to the demographic of people who learn just the syntax of a language and then pretend that they know it. I think it should be possible to write : > auto MyResult= "my,csv,line"s.split(","); > myvar=MyResult[1]; > for(auto sv : MyResult) > > Here is what that code would look like under the guidelines I (and others) outlined previously: vector MyResult(split("my,csv,line", ",")); myvar = MyResult[1]; for(auto sv : MyResult) See how simple that is? This only allocates memory in `vector`'s constructor (so you're not needlessly allocating a `basic_string`, just for a string literal). Plus, if you just want the iteration, without the need for random access: for(auto sv : split("my,csv,line", ",")) This performs *zero* memory allocations. Why *shouldn't* this be the default? In C++, the default ought to be fast, where possible. Perhaps having multiple (like for stoi,l,ll) could be an option > No. A single function returning a range, as outlined above, can cover all of these cases effectively. -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/172d08f0-a3da-4b9e-bfdd-985fb1f527c8%40isocpp.org. ------=_Part_688_969289153.1482680504224 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Sunday, December 25, 2016 at 5:32:44 AM UTC-5, lnal...@= gmail.com wrote:

Hello,


Most of modern language (D, Python, Java, C#, Go, Ru= st) got a split=20 method on their string type, so I think it really make sense to have someth= ing=20 similar in C++.


All of those languages a= lso only have a single string type. C++ has hundreds. Even the st= andard library has 2, and that doens't even count `const char*`.
Having a `split` function that can only be used with the standa= rd library string types is pathetic. Especially when it could be made to be= used with any string type (that provides a conversion to `string_view`) wi= th ease.

If you want to suggest that `basic_string` and `string_view= ` should have member versions that call the non-member algorithms, fine. Bu= t the non-member function is where the actual work happens.
=C2=A0
=

All of the= m returns a 'vector' and I think is the main waited=20 result.


No.

While we should not be ig= norant of what other languages are doing, we also should not pretend that t= he design of other languages is a priori correct for C++. We should do what= is best for C++.

And one principle of C++ is that we do not make pe= ople pay for features they don't need to use. Forcing the return of a `= vector` makes people pay for memory allocations that they may not use.
<= br>

I= think it should=20 not be required to mastering all subtilities of the STL to do something a s= imple=20 as that.


Master the subtleties of what? Of u= sing a range? That should be an early lesson for C++ programmers; it's = hardly deep metaprogramming magic.

If you're going to be able to= work in a language, you need to know its idioms. And ranges are ver= y important idioms in C++. We shouldn't cater to the demographic of peo= ple who learn just the syntax of a language and then pretend that they know= it.

I think it should be possible to write :

auto MyResult=3D<= span style=3D"color:#000"> "my,csv,l= ine"s.split(",");
myvar=3DMyResult[1];
for(auto sv : MyResult)


He= re is what that code would look like under the guidelines I (and others) ou= tlined previously:

vector MyResult(split(= "my,c= sv,line", ","));
myvar =3D MyResult[1];
for(= auto sv : MyResult)

See how sim= ple that is? This only allocates memory in `vector`'s constructor (so y= ou're not needlessly allocating a `basic_string`, just for a string lit= eral).

Plus, if you just want the iteration, without the need for ra= ndom access:

<= div class=3D"subprettyprint">for(auto= sv : split("my,csv,line", ","))

This pe= rforms zero memory allocations. Why shouldn't this be the= default? In C++, the default ought to be fast, where possible.

Perhaps having multiple (like for stoi,l,ll) could be an option


No. A single function returning a range, as o= utlined above, can cover all of these cases effectively.

--
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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/172d08f0-a3da-4b9e-bfdd-985fb1f527c8= %40isocpp.org.
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