220 36853 article Path: news.gmane.org!.POSTED!not-for-mail From: Jake Arkinstall Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: String interpolation Date: Fri, 9 Feb 2018 21:13:07 +0000 Lines: 261 Approved: news@gmane.org Message-ID: References: <356d5835-f1bf-4699-94f5-0b2d3d0b9c0e@isocpp.org> <25CCF885-86AD-4D51-8F5C-C46376D34DE0@gmail.com> <4890431.TR9UepuQra@tjmaciei-mobl1> <1cdb6300-7397-46d7-bce9-62e6e8dac40b@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="001a11c0327aba08bb0564cdfe15" X-Trace: blaine.gmane.org 1518210686 9621 195.159.176.226 (9 Feb 2018 21:11:26 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 9 Feb 2018 21:11:26 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDCZX3WUUQFRBZE57DJQKGQEOJ5REWA@isocpp.org Fri Feb 09 22:11:21 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ot0-f199.google.com ([74.125.82.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1ekFwm-0001BQ-Ho for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id d186sor1356628oia.52.2018.02.09.13.13.08 for (Google Transport Security); Fri, 09 Feb 2018 13:13:08 -0800 (PST) Received-SPF: pass (google.com: domain of jake.arkinstall@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.202.4.204 with SMTP id 195mr2849658oie.262.1518210788229; Fri, 09 Feb 2018 13:13:08 -0800 (PST) Original-Received: by 10.168.151.129 with HTTP; Fri, 9 Feb 2018 13:13:07 -0800 (PST) Original-Received: by 10.168.151.129 with HTTP; Fri, 9 Feb 2018 13:13:07 -0800 (PST) In-Reply-To: <1cdb6300-7397-46d7-bce9-62e6e8dac40b@isocpp.org> X-Original-Sender: jake.arkinstall@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=OY7QlqWw; spf=pass (google.com: domain of jake.arkinstall@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=jake.arkinstall@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:36853 Archived-At: --001a11c0327aba08bb0564cdfe15 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On 9 Feb 2018 20:51, wrote: Minimal version than could be added to C++ is new string prefix `F` (because we have `R`, `u`, `u8` and `U` already, and `$` is outside of source characters) that enable mixing code with string literals. As Marcel Kr=C3=BCger wrote, language could transform this string literal t= o: F"testA{a}test{{B}}"_x; =3D> operator""_x("testA"_x, a, "test{B}"_x); //usi= ng same postfix to parse sub-literals FR"aa(x{b}y)aa"_x; =3D> operator""_x(R"aa(x)aa"_x, b, R"aa(y)aa"_x); //it have precedence over `R` prefix Rest will be implemented by library, this mean `F"a {5} b"` will not compile because there is no matching operator. stl could add this operator for `s` postfix, that will use `std::to_string` for conversing all arguments: template std::string operator""s(Parts&&... p) { return std::to_string(std::forward< Parts>(p)) + ...; } int main() { auto x =3D F"Test {{a}} =3D {10+5}"s; //x =3D=3D "Test {a} =3D 15"s } No iosteam, and even more it could if someone relay desire to have localizations: F"Test {356*10}"_loc("Prod {0} OK!", "fr") =3D=3D "Prod 3.560,00 OK!"; Only drawback is some template bloat but this is probably acceptable cost. This is exactly the kind of thing I'm aiming for, although I dont believe string conversion and concatenation to be the final solution - unless my recall of benchmarks is out of date, streams are faster than string concatenation. This being said, similar ideas can be applied to utilise the fmt library, for example. --=20 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 e= mail 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/CAC%2B0CCOSZHaTA%3DYPSDU8Add7mE_BYcYPRCmGW8TRPtZ= hdqL8Hw%40mail.gmail.com. --001a11c0327aba08bb0564cdfe15 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On 9 Feb 2018 20:51, <inkwizytoryankes@gmail.com> wrote:

Minimal version than could be added to C++ is new string prefix `F` = (because we have `R`, `u`, `u8` and `U` already, and `$` is outside of sour= ce characters) that enable mixing code with string literals.
As Marcel K= r=C3=BCger wrote, language could transform this string literal to:
F"testA{a}test{{B}}"_x; =3D> operator= ""_x("testA"_x, a, "test{B}"<= span style=3D"color:#000" class=3D"m_9005655817011445617styled-by-prettify"= >_x); //using same postfix to parse sub-literals=
FR"aa(x{b}y)aa"_x;= =3D> operator""<= span style=3D"color:#000" class=3D"m_9005655817011445617styled-by-prettify"= >_x(R"aa(x)aa"_x, b, R"aa(y)aa"_x= ); //it have precedence over `R` prefix



Rest will be implemented by library, this mean `F&quo= t;a {5} b"` will not compile because there is no matching operator. st= l could add this operator for `s` postfix, that will use `std::to_string` f= or conversing all arguments:
template= <typename... Parts= >
std::string operator<= /span>""s(Parts&&..= .. p) { return<= span style=3D"color:#000" class=3D"m_9005655817011445617styled-by-prettify"= > std::to_string(std::forward<Parts>(p<= span style=3D"color:#660" class=3D"m_9005655817011445617styled-by-prettify"= >)) + ...; }<= span style=3D"color:#000" class=3D"m_9005655817011445617styled-by-prettify"= >

int main()
{
=C2=A0 =C2=A0 auto x =3D F"Test {{a}} =3D {10+5}"s; = //x =3D=3D "Test {a} =3D 15"s
}
No iosteam, and even more it could if som= eone relay desire to have localizations:

F"Test {356*10}"_loc(<= span style=3D"color:#080" class=3D"m_9005655817011445617styled-by-prettify"= >"Prod {0} OK!", "fr") =3D=3D "Prod 3.560,00 OK!&quo= t;;

Only drawback is som= e template bloat but this is probably acceptable cost.

= This is exactly the kind of thing I'm aiming for, although I dont belie= ve string conversion and concatenation to be the final solution - unless my= recall of benchmarks is out of date, streams are faster than string concat= enation.

This being said= , similar ideas can be applied to utilise the fmt library, for example.

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