220 36860 article Path: news.gmane.org!.POSTED!not-for-mail From: Jake Arkinstall Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: String interpolation Date: Sat, 10 Feb 2018 13:31:46 +0000 Lines: 312 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="001a113ceaeea848c80564dbaa41" X-Trace: blaine.gmane.org 1518269406 2521 195.159.176.226 (10 Feb 2018 13:30:06 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 10 Feb 2018 13:30:06 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDCZX3WUUQFRBRHI7PJQKGQETPKJV2Q@isocpp.org Sat Feb 10 14:30:02 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 1ekVDr-0007pN-Uo for gclcip-std-proposals@m.gmane.org; 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[209.85.220.65]) by mx.google.com with SMTPS id 25sor1857339oir.105.2018.02.10.05.31.47 for (Google Transport Security); Sat, 10 Feb 2018 05:31:47 -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 10.202.168.14 with SMTP id r14mr4114451oie.289.1518269507322; Sat, 10 Feb 2018 05:31:47 -0800 (PST) Original-Received: by 10.168.151.129 with HTTP; Sat, 10 Feb 2018 05:31:46 -0800 (PST) Original-Received: by 10.168.151.129 with HTTP; Sat, 10 Feb 2018 05:31:46 -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=aa0OgCmE; 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:36860 Archived-At: --001a113ceaeea848c80564dbaa41 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Im a bit confused about the suggestion but it appears that the input is an int, where the name and age are outputs. In this scenario, the _sql parser (provided by some library) could convert that to db.run("select name, age from table where id =3D " + db::int_input(id), db::string_output(name), db::int_output(age)); which sets the name and age variables to the name and age columns. Adding sql sanitisers is then done via the db::*_input methods. It just might be possible. It would require a lot of compile-time parsing, and so a proposal to allow this would probably need to include a bunch of mechanisms to process string literals at compile time, but it's interesting. I'm not sure about that exact idea, but the point is the creativity - a way of a library being able to parse a string literal, putting code in its place which in turn gets compiled, would give a lot more flexibility to libraries, and let them get very creative. It could open the door to libraries providing syntactic sugar that still provides efficient code. A language within a language. On 10 Feb 2018 05:30, "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 litera= l 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); //i= t >> 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 operat= or >> 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 cos= t. >> >> >> This is exactly the kind of thing I'm aiming for, although I dont believ= e >> 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 ? Indeed, this seems like a justification to *not* provide this feature. --=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 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/f5feb9a0-99d3-433a- ae46-af34c8d00a61%40isocpp.org .. --=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%2B0CCM-e6Ghg_KOGP9Cpm5NKvgkLSpcyV05%2BksP2Pm= VBzXoQw%40mail.gmail.com. --001a113ceaeea848c80564dbaa41 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Im a bit confused about the suggestion but it appear= s that the input is an int, where the name and age are outputs. In this sce= nario, the _sql parser (provided by some library) could convert that to

db.run("select name, a= ge from table where id =3D " + db::int_input(id), db::string_output(na= me), db::int_output(age));

which sets the name and age variables to the name and age columns. Addin= g sql sanitisers is then done via the db::*_input methods. It just might be= possible. It would require a lot of compile-time parsing, and so a proposa= l to allow this would probably need to include a bunch of mechanisms to pro= cess string literals at compile time, but it's interesting.

I'm not sure about that exact i= dea, but the point is the creativity - a way of a library being able to par= se a string literal, putting code in its place which in turn gets compiled,= would give a lot more flexibility to libraries, and let them get very crea= tive. It could open the door to libraries providing syntactic sugar that st= ill provides efficient code. A language within a language.


On 10 Feb 2018 05:30, "Nicol Bolas" <jmckesson@gmail.com> wrote:
<= br>
On Friday, February 9, 2018 at 5:12:26 PM UTC-5, Marcin Jaczewski wr= ote:


On Fri= day, 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 str= ing 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}}&quo= t;_x; =3D><= /span> operato= r""_x("testA"_x, a, "test{B}"_x); //using same postfix to parse sub-literals
FR"aa(x{b}y)aa= "_x; =3D&= gt; ope= rator""_x(R"aa(x)aa"_x, b, R"aa(y)aa"<= span style=3D"color:#000">_x); //it have precede= nce over `R` prefix



Rest will be imple= mented by library, this mean `F"a {5} b"` will not compile becaus= e there is no matching operator. stl could add this operator for `s` postfi= x, that will use `std::to_string` for conversing all arguments:
templ= ate<= typename... 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"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 ex= actly 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, on= ly 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<= /span>"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 boun= d parameters or otherwise sanitize string inputs? Have we learned nothing f= rom Little Bobby Tables= ?

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

--
You received this message because you are subscribed to the Google Groups &= quot;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/f5fe= b9a0-99d3-433a-ae46-af34c8d00a61%40isocpp.org.

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You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
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To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAC%2B0CCM-e6= Ghg_KOGP9Cpm5NKvgkLSpcyV05%2BksP2PmVBzXoQw%40mail.gmail.com.
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