220 36866 article Path: news.gmane.org!.POSTED!not-for-mail From: Jake Arkinstall Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: String interpolation Date: Sun, 11 Feb 2018 13:13:07 +0000 Lines: 414 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> <4bce681e-e729-4124-9322-69291fdb6678@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="001a1135615cc9d9c10564ef8543" X-Trace: blaine.gmane.org 1518354678 26508 195.159.176.226 (11 Feb 2018 13:11:18 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 11 Feb 2018 13:11:18 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDCZX3WUUQFRBZMCQHKAKGQEHZVRVII@isocpp.org Sun Feb 11 14:11:14 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f70.google.com ([209.85.218.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1ekrPM-0005zq-J7 for gclcip-std-proposals@m.gmane.org; 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[209.85.220.65]) by mx.google.com with SMTPS id e16sor1391248otj.19.2018.02.11.05.13.08 for (Google Transport Security); Sun, 11 Feb 2018 05:13:08 -0800 (PST) Received-SPF: pass (google.com: domain of jake.arkinstall@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; X-Received: by 10.157.7.76 with SMTP id 70mr7224915ote.257.1518354788111; Sun, 11 Feb 2018 05:13:08 -0800 (PST) Original-Received: by 10.168.151.129 with HTTP; Sun, 11 Feb 2018 05:13:07 -0800 (PST) Original-Received: by 10.168.151.129 with HTTP; Sun, 11 Feb 2018 05:13:07 -0800 (PST) In-Reply-To: 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=R9Izn0EA; spf=pass (google.com: domain of jake.arkinstall@gmail.com designates 209.85.220.65 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:36866 Archived-At: --001a1135615cc9d9c10564ef8543 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Horrible is... subjective. Such ideas are dangerous in weak hands, but are nonetheless available in most interpreted languages. I like other approach just because it's more in tune with the direction the language is already going in, but the power of compile-time code injection is intriguing. In order to make it see it's potential we'd have to add a bunch of constexpr string functions. On 11 Feb 2018 13:06, "Avi Kivity" wrote: > On 02/10/2018 07:30 AM, Nicol Bolas wrote: > > > > On Friday, February 9, 2018 at 5:12:26 PM UTC-5, Marcin Jaczewski wrote: >> >> >> >> On Friday, February 9, 2018 at 10:13:10 PM UTC+1, Jake Arkinstall wrote: >>> >>> >>> >>> 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 liter= al to: >>> F"testA{a}test{{B}}"_x; =3D> operator""_x("testA"_x, a, "test{B}"_x); /= /using >>> 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 opera= tor >>> 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(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. >>> >> >> This is irrelevant, how it will be implemented is QoI, It could be done >> using `snprintf`, or even not implemented at all, only prefix `F`and its >> transformation is important. >> >> More I think about this more it look as great addition to language: >> std::string a; >> int b =3D 0; >> int c =3D 42; >> db.run(F"select name as {a}, age as {b} from table where id =3D {c}"_sql= ); >> >> > If how this is implemented is a mere implementation detail, how would you > make it use bound parameters or otherwise sanitize string inputs? Have we > learned nothing from Little Bobby Tables ? > > > > My horrible code injection proposal would make it work. It would transfor= m > the thingie above into "prepare_and_execute("select name as ?, age as ? > from table where id =3D ?", a, b, c)" (ignoring the bad SQL for a minute)= .. > > > > > > Indeed, this seems like a justification to *not* provide this feature. > > > -- > 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/ff46a2e5-cf65-7612- > a284-6163e53b9bc3%40scylladb.com > > . > --=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%2B0CCNZXxi9DsmADBbC9Ov6JQrcJHzPdDLtCe7_4-6yO= i%3DGxA%40mail.gmail.com. --001a1135615cc9d9c10564ef8543 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Horrible is... subjective. Such ideas are dangerous in we= ak hands, but are nonetheless available in most interpreted languages.

I like other approach just because= it's more in tune with the direction the language is already going in,= but the power of compile-time code injection is intriguing. In order to ma= ke it see it's potential we'd have to add a bunch of constexpr stri= ng functions.

On 11 Feb 2018 13:06, "Avi Kivity" <avi@scylladb.com> wrote:
<= blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px= #ccc solid;padding-left:1ex"> =20 =20 =20
On 02/10/2018 07:30 = AM, Nicol Bolas wrote:


On Friday, February 9, 2018 at 5:12:26 PM UTC-5, Marcin Jaczewski wrote:


On Friday, February 9, 2018 at 10:13:10 PM UTC+1, Jake Arkinstall wrote:


On 9 Feb 2018 20:51, <inkwizyt...@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 source characters) that enable mixing code with string literals.
As Marcel Kr=C3=BCger wrote, language could transform this string literal to:
F"testA{a}test{{B}}"_x; =3D> operator""_x("testA"_x, a, "test{B}"= _x); //using s= ame postfix to parse sub-literals
FR&qu= ot;aa(x{b}y)aa"_x; =3D> operator""_x(R"aa(x)aa"= _x, b,<= span style=3D"color:#000"> R"aa(y)aa= "_x); //i= t have precedence over `R` prefix



Rest will be implemented by library, this mean `F"a {5} b"` will not compile be= cause there is no matching operator. stl could add this operator for `s` postfix, that will use `std::to_string` for conversing all arguments:
template<typena= me... <= /span>Parts>= ;
std::= string = operator""s(Parts&&... p) { return std::to_string(std::forward<Parts>(p)) + ...; }

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 someone relay desire to have localizations:

F<= span style=3D"color:#080">"Test {356*10}"_loc("Prod {0} OK!",<= span style=3D"color:#000"> "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.
=C2=A0
This is irrelevant, how it will be implemented is QoI, It could be done using `snprintf`, or even not implemented at all, only prefix `F`and its transformation is important.

More I think about this more it look as great addition to language:
std::string a;
int b =3D 0;
int c =3D 42;
db.run(F"select name as {a}= , age as {b} from table where id =3D {c}"_sql);


If how this is implemented is a mere implementation detail, how would you make it use bound parameters or otherwise sanitize string inputs? Have we learned nothing from Little Bobby Tables?



My horrible code injection proposal would make it work. It would transform the thingie above into "prepare_and_execute("select= name as ?, age as ? from table where id =3D ?", a, b, c)" (ignorin= g the bad SQL for a minute).





Indeed, this seems like a justification to not provide this feature.

--
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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/ff= 46a2e5-cf65-7612-a284-6163e53b9bc3%40scylladb.com.

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