220 40265 <952795b3-b87b-4140-b4f2-2c9ad968b2f7@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Adrian H Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: std::between ? 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Fri, 28 Sep 2018 15:47:15 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a25:388b:: with SMTP id f133-v6ls2263720yba.10.gmail; Fri, 28 Sep 2018 15:47:14 -0700 (PDT) X-Received: by 2002:a25:50c7:: with SMTP id e190-v6mr5271ybb.1.1538174834388; Fri, 28 Sep 2018 15:47:14 -0700 (PDT) In-Reply-To: X-Original-Sender: adrian.hawryluk@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:40265 Archived-At: ------=_Part_581_1508307572.1538174833905 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Friday, September 28, 2018 at 11:25:30 AM UTC-4, Daniel Gutson wrote: > El vie., 28 de sep. de 2018 a la(s) 12:18, Adrian H (adrian....@gmail.com= ) escribi=C3=B3: >=20 > #include > #include >=20 >=20 > template > struct chain_impl { > =C2=A0 chain_impl(T&& obj, bool val) : obj(std::move(obj)), val(val) {} > =C2=A0 T&& obj; > =C2=A0 bool val; > =C2=A0 explicit operator bool() { > =C2=A0 =C2=A0 =C2=A0 return val; > =C2=A0 } > }; >=20 >=20 > template > struct chain_impl { > =C2=A0 chain_impl(T& obj, bool val) : obj(obj), val(val) {} > =C2=A0 T& obj; > =C2=A0 bool val; > =C2=A0 explicit operator bool() { > =C2=A0 =C2=A0 =C2=A0 return val; > =C2=A0 } > }; >=20 >=20 > template > decltype(auto) make_chain(T&&=C2=A0 obj, bool val =3D true) { > =C2=A0 return chain_impl::= value, T&, T&&>>(std::forward(obj), val); > } >=20 >=20 > template > auto operator< (chain_impl&& lhs, T1&& rhs) { > =C2=A0 =C2=A0 if (lhs.val) { >=20 >=20 > Why you say that comparisons are performed? You are breaking the chain he= re with this evaluation. So yes, operator will keep be called, but it's jus= t this if. So maybe not a comparison, but still a flag check for each comparison, rega= rdless if it reached a potential short circuit point. Also, an extra Boolea= n would be needed to be allocated for each term. Unless you're saying that the optimizer will be able to detect this and sho= rt circuit the operation and not allocate the Booleans? That would be nice,= but I don't have that much faith in the optimizer. So unless it can optimi= ze that code and data away then this feature would have to be on the compil= er level so as not to add extra crap to the final binary. > =C2=A0 >=20 > =C2=A0 =C2=A0 =C2=A0 =C2=A0 auto result =3D make_chain(rhs, lhs.obj < rhs= ); > =C2=A0 =C2=A0 =C2=A0 =C2=A0 return make_chain(std::forward(rhs), lhs.= val && result.val); > =C2=A0 =C2=A0 } > =C2=A0 =C2=A0 return make_chain(std::forward(rhs), false); > } >=20 >=20 > int main() > { > =C2=A0 std::cout << (make_chain(1) < 2 < 3 ? 1 : 0) << "\n"; > =C2=A0 int a=3D1, b=3D2, c=3D3; >=20 > =C2=A0 std::cout << (make_chain(a) < c < b ? 1 : 0) << "\n"; > } >=20 >=20 > Looking forward to seeing the difference. Sorry. I don't understand your comment here. >=20 > =C2=A0 >=20 >=20 >=20 >=20 >=20 >=20 >=20 >=20 >=20 > and additional storage for bool propagation (though I've not looked at wh= at the optimizer would do).=C2=A0 Would prolly be better to implement in th= e language to avoid those issues, even if it is only syntactic sugar, as it= can make the code more readable. > =C2=A0 >=20 >=20 >=20 >=20 >=20 > El jue., 27 de sep. de 2018 a la(s) 12:53, Addy (acl...@gmail.com) escrib= i=C3=B3: >=20 > I do this pattern often: >=20 >=20 > if (0 < x && x < 100) >=20 >=20 > And would love a simple `std::between()` that would take two arguments an= d an optional third (compare function) argument. >=20 >=20 > Similar to this:=C2=A0https://gist.github.com/martinmoene/9410391 >=20 >=20 >=20 > templated > bool std::between(T lower, T upper, Compare comp) > { > =C2=A0 =C2=A0 return comp(lower) && comp(upper); > } >=20 >=20 > Does anything like this exist? Should I propose it!? >=20 >=20 >=20 >=20 > --=20 >=20 > You received this message because you are subscribed to the Google Groups= "ISO C++ Standard - Future Proposals" group. >=20 > To unsubscribe from this group and stop receiving emails from it, send an= email to std-proposal...@isocpp.org. >=20 > To post to this group, send email to std-pr...@isocpp.org. >=20 > To view this discussion on the web visit https://groups.google.com/a/isoc= pp.org/d/msgid/std-proposals/7b85d688-9013-407d-b7d3-10d28494e960%40isocpp.= org. >=20 >=20 >=20 >=20 > --=20 >=20 > Who=E2=80=99s got the sweetest disposition? > One guess, that=E2=80=99s who? > Who=E2=80=99d never, ever start an argument? > Who never shows a bit of temperament? > Who's never wrong but always right? > Who'd never dream of starting a fight? > Who get stuck with all the bad luck?=20 >=20 >=20 >=20 >=20 >=20 > --=20 >=20 > You received this message because you are subscribed to the Google Groups= "ISO C++ Standard - Future Proposals" group. >=20 > To unsubscribe from this group and stop receiving emails from it, send an= email to std-proposal...@isocpp.org. >=20 > To post to this group, send email to std-pr...@isocpp.org. >=20 > To view this discussion on the web visit https://groups.google.com/a/isoc= pp.org/d/msgid/std-proposals/b917d650-33b0-459d-bba0-c0f03bc4db8d%40isocpp.= org. >=20 >=20 >=20 >=20 >=20 >=20 >=20 > --=20 >=20 > You received this message because you are subscribed to the Google Groups= "ISO C++ Standard - Future Proposals" group. >=20 > To unsubscribe from this group and stop receiving emails from it, send an= email to std-proposal...@isocpp.org. >=20 > To post to this group, send email to std-pr...@isocpp.org. >=20 > To view this discussion on the web visit https://groups.google.com/a/isoc= pp.org/d/msgid/std-proposals/52d6bd1b-4afb-4f16-adde-8ee8b5ba1041%40isocpp.= org. >=20 >=20 >=20 >=20 > --=20 >=20 > Who=E2=80=99s got the sweetest disposition? > One guess, that=E2=80=99s who? > Who=E2=80=99d never, ever start an argument? > Who never shows a bit of temperament? > Who's never wrong but always right? > Who'd never dream of starting a fight? > Who get stuck with all the bad luck?=20 >=20 >=20 >=20 >=20 >=20 > --=20 >=20 > You received this message because you are subscribed to the Google Groups= "ISO C++ Standard - Future Proposals" group. >=20 > To unsubscribe from this group and stop receiving emails from it, send an= email to std-proposal...@isocpp.org. >=20 > To post to this group, send email to std-pr...@isocpp.org. >=20 > To view this discussion on the web visit https://groups.google.com/a/isoc= pp.org/d/msgid/std-proposals/bacc5cd9-230a-4865-858c-78566502cfef%40isocpp.= org. >=20 >=20 >=20 >=20 > --=20 >=20 > Who=E2=80=99s got the sweetest disposition? > One guess, that=E2=80=99s who? > Who=E2=80=99d never, ever start an argument? > Who never shows a bit of temperament? > Who's never wrong but always right? > Who'd never dream of starting a fight? > Who get stuck with all the bad luck? --=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/952795b3-b87b-4140-b4f2-2c9ad968b2f7%40isocpp.or= g. ------=_Part_581_1508307572.1538174833905-- .