220 40256 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 08:18:07 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a25:8b0c:: with SMTP id i12-v6ls2184095ybl.5.gmail; Fri, 28 Sep 2018 08:18:06 -0700 (PDT) X-Received: by 2002:a25:50c7:: with SMTP id e190-v6mr179846ybb.1.1538147886075; Fri, 28 Sep 2018 08:18:06 -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:40256 Archived-At: ------=_Part_132_735510085.1538147885385 Content-Type: multipart/alternative; boundary="----=_Part_133_1444313961.1538147885386" ------=_Part_133_1444313961.1538147885386 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Friday, September 28, 2018 at 10:53:35 AM UTC-4, Daniel Gutson wrote: > > > > El vie., 28 de sep. de 2018 a la(s) 11:40, Adrian H (adrian....@gmail.com= =20 > ) escribi=C3=B3: > >> >> >> On Friday, September 28, 2018 at 10:31:57 AM UTC-4, Daniel Gutson wrote: >>> >>> >>> >>> El vie., 28 sept. 2018 11:26, Jack Adrian Zappa = =20 >>> escribi=C3=B3: >>> >>>> >>>> >>>> On Friday, September 28, 2018 at 7:03:19 AM UTC-4, Daniel Gutson wrote= : >>>>> >>>>> I stepped into this too many times. >>>>> One of the issues are the four < vs <=3D combinations. >>>>> >>>>> The way I solved is by creating a temporal object that allows chain= =20 >>>>> comparison, and a cast-to-bool operator. >>>>> >>>>> if (chain(3) < x < 4)=20 >>>>> >>>> >>>> So, something similar to the solution I provided? As I said, that=20 >>>> solution would probably result in possible unnecessary comparisons (no= =20 >>>> logical short circuiting)=20 >>>> >>> >>> No, the chain object contains a boolean and the last right hand operand= =20 >>> as its only state. It should do nothing after the boolean becomes false= .. >>> >> >> Could you provide your solution? I'd be interested in finding out how= =20 >> you dealt with short circuiting. =20 >> > > Sure, I'm in a conference but I will do later. > =20 > >> Also, I take it that your solution wouldn't allow comparisons of=20 >> different types such as a double and a float, or would it convert all=20 >> objects to the type of first one chained?=20 >> > > Both the chain class and the comparison operators are templates. The=20 > result of the operator is a new (temporal) chain object with the template= =20 > argument deduced. Let me provide the code later.=20 > Cool. Still sounds very similar to what I posted: #include #include template struct chain_impl { chain_impl(T&& obj, bool val) : obj(std::move(obj)), val(val) {} T&& obj; bool val; explicit operator bool() { return val; } }; template struct chain_impl { chain_impl(T& obj, bool val) : obj(obj), val(val) {} T& obj; bool val; explicit operator bool() { return val; } }; template decltype(auto) make_chain(T&& obj, bool val =3D true) { return chain_impl::value,= =20 T&, T&&>>(std::forward(obj), val); } template auto operator< (chain_impl&& lhs, T1&& rhs) { if (lhs.val) { auto result =3D make_chain(rhs, lhs.obj < rhs); return make_chain(std::forward(rhs), lhs.val && result.val); } return make_chain(std::forward(rhs), false); } int main() { std::cout << (make_chain(1) < 2 < 3 ? 1 : 0) << "\n"; int a=3D1, b=3D2, c=3D3; std::cout << (make_chain(a) < c < b ? 1 : 0) << "\n"; } Looking forward to seeing the difference. =20 > =20 > >> >> >>> and additional storage for bool propagation (though I've not looked at= =20 >>>> what the optimizer would do). Would prolly be better to implement in = the=20 >>>> language to avoid those issues, even if it is only syntactic sugar, as= it=20 >>>> can make the code more readable. >>>> =20 >>>> >>>>> >>>>> >>>>> El jue., 27 de sep. de 2018 a la(s) 12:53, Addy (acl...@gmail.com)=20 >>>>> escribi=C3=B3: >>>>> >>>>>> I do this pattern often: >>>>>> >>>>>> if (0 < x && x < 100) >>>>>> >>>>>> And would love a simple `std::between()` that would take two=20 >>>>>> arguments and an optional third (compare function) argument. >>>>>> >>>>>> Similar to this: https://gist.github.com/martinmoene/9410391 >>>>>> >>>>>> templated >>>>>> bool std::between(T lower, T upper, Compare comp) >>>>>> { >>>>>> return comp(lower) && comp(upper); >>>>>> } >>>>>> >>>>>> Does anything like this exist? Should I propose it!? >>>>>> >>>>>> --=20 >>>>>> You received this message because you are subscribed to the Google= =20 >>>>>> Groups "ISO C++ Standard - Future Proposals" group. >>>>>> To unsubscribe from this group and stop receiving emails from it,=20 >>>>>> send an email to std-proposal...@isocpp.org. >>>>>> To post to this group, send email to std-pr...@isocpp.org. >>>>>> To view this discussion on the web visit=20 >>>>>> https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/7b85d68= 8-9013-407d-b7d3-10d28494e960%40isocpp.org=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 >>>> You received this message because you are subscribed to the Google=20 >>>> Groups "ISO C++ Standard - Future Proposals" group. >>>> To unsubscribe from this group and stop receiving emails from it, send= =20 >>>> an email to std-proposal...@isocpp.org. >>>> To post to this group, send email to std-pr...@isocpp.org. >>>> To view this discussion on the web visit=20 >>>> https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/b917d650-= 33b0-459d-bba0-c0f03bc4db8d%40isocpp.org=20 >>>> >>>> . >>>> >>> --=20 >> You received this message because you are subscribed to the Google Group= s=20 >> "ISO C++ Standard - Future Proposals" group. >> To unsubscribe from this group and stop receiving emails from it, send a= n=20 >> email to std-proposal...@isocpp.org . >> To post to this group, send email to std-pr...@isocpp.org . >> To view this discussion on the web visit=20 >> https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/52d6bd1b-4a= fb-4f16-adde-8ee8b5ba1041%40isocpp.org=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 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/bacc5cd9-230a-4865-858c-78566502cfef%40isocpp.or= g. ------=_Part_133_1444313961.1538147885386 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Friday, September 28, 2018 at 10:53:35 AM UTC-4= , Daniel Gutson wrote:


El vie., 28 de= sep. de 2018 a la(s) 11:40, Adrian H (adrian....@gmail.com) escribi=C3=B3= :


On Frida= y, September 28, 2018 at 10:31:57 AM UTC-4, Daniel Gutson wrote:


El vie., 28 sept. 2018 11:26, Jack Adrian Zapp= a <adrian....@gmail.com> escribi=C3=B3:


On Friday, Sept= ember 28, 2018 at 7:03:19 AM UTC-4, Daniel Gutson wrote:
I stepped into this too many times.=
One of the issues are the four < vs <=3D combinations.

The way I solved is by creating a temporal object that allo= ws chain comparison, and a cast-to-bool operator.

= if (chain(3) < x < 4)=C2=A0

So, something similar to the solution I provided?=C2=A0 As I said, that = solution would probably result in possible unnecessary comparisons (no logi= cal short circuiting)

No, the chain object contains a boolean and t= he last right hand operand as its only state. It should do nothing after th= e boolean becomes false.

Could = you provide your solution?=C2=A0 I'd be interested in finding out how y= ou dealt with short circuiting.=C2=A0

Sure, I'm in a conference but I will do later.
=C2=A0=
Also, I take it = that your solution wouldn't allow comparisons of different types such a= s a double and a float, or would it convert all objects to the type of firs= t one chained?=C2=A0

Both the c= hain class and the comparison operators are templates. The result of the op= erator is a new (temporal) chain object with the template argument deduced.= Let me provide the code later.=C2=A0
Cool.=C2=A0 Still sounds very similar to what I posted:
<= div>
#include <iostrea= m>
#include <typ= e_traits>

template<typename T>=
struct chain_impl {
=C2=A0 chain_impl(T&= ;& obj, bool val) : obj(std::move(obj)), val(val) {}
<= font face=3D"monospace, monospace">=C2=A0 T&& obj;
=C2=A0 bool val;
=C2=A0 explicit operator bool() {
=C2=A0 =C2=A0 =C2=A0 return val= ;
=C2=A0 }
};

template<typename T>
struct chain_impl<T&> {
=C2=A0 chain_impl(T& obj, bool val) : obj(obj), = val(val) {}
=C2=A0 T&a= mp; obj;
=C2=A0 bool v= al;
=C2=A0 explicit op= erator bool() {
=C2=A0= =C2=A0 =C2=A0 return val;
=C2=A0 }
};

template <typename T>
decltype(auto) make_chain(T&&= =C2=A0 obj, bool val =3D true) {
=C2=A0 return chain_impl<std::conditional_t<std::is_l= value_reference<T>::value, T&, T&&>>(std::forw= ard<T>(obj), val);
}

=
template <typename T0, typename= T1>
auto operator&= lt; (chain_impl<T0>&& lhs, T1&& rhs) {
=C2=A0 =C2=A0 if (lhs.val) {<= /div>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 a= uto result =3D make_chain(rhs, lhs.obj < rhs);
=C2=A0 =C2=A0 =C2=A0 =C2=A0 return make_chain(s= td::forward<T1>(rhs), lhs.val && result.val);
=C2=A0 =C2=A0 }
=C2=A0 =C2=A0 return make_chain(std::f= orward<T1>(rhs), false);
}

int main()
=
{
=C2=A0 std::cout << (make_chain(1) < 2 < 3= ? 1 : 0) << "\n";
=C2=A0 int a=3D1, b=3D2, c=3D3;
=C2=A0 std::cout << (make_c= hain(a) < c < b ? 1 : 0) << "\n";
}

Looking forward to seeing the difference.
=C2=A0
=C2=A0

<= div dir=3D"auto">
and additional storage fo= r bool propagation (though I've not looked at what the optimizer would = do).=C2=A0 Would prolly be better to implement in the language to avoid tho= se issues, even if it is only syntactic sugar, as it can make the code more= readable.
=C2=A0


El jue., 27 de sep. de 2018 a la(s) 12:53, Addy (acl...@gmail.com) escribi=C3=B3:
I do this pattern often:

if (0 < x && x < 100)

And would lo= ve a simple `std::between()` that would take two arguments and an optional = third (compare function) argument.


templated<= ;typename T, typename Compare>
bool std::between(T lower, T up= per, Compare comp)
{
=C2=A0 =C2=A0 return comp(lower) &= amp;& comp(upper);
}

Does anything l= ike this exist? Should I propose it!?

--
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-proposal...@isocpp.org.
To post to this group, send email to std-pr.= ...@isocpp.org.
To view this discussion on the web visit https://groups.google.com= /a/isocpp.org/d/msgid/std-proposals/7b85d688-9013-407d-b7d3-= 10d28494e960%40isocpp.org.


--
Who=E2=80=99s got the sweetest disposition?
One guess, that=E2=80=99s w= ho?
Who=E2=80=99d never, ever start an argument?
Who never shows a bi= t of temperament?
Who's never wrong but always right?
Who'd n= ever dream of starting a fight?
Who get stuck with all the bad luck?

--
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-proposal...@isocpp.org.
To post to this group, send email to std-pr...@isocpp.o= rg.
To view this discussion on the web visit https://groups.google.com= /a/isocpp.org/d/msgid/std-proposals/b917d650-33b0-459d-bba0-= c0f03bc4db8d%40isocpp.org.

--
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-proposal...@isocpp.org.
To post to this group, send email to std-pr...@isocpp.org.
To view this discussion on the web visit https://groups.google.com= /a/isocpp.org/d/msgid/std-proposals/52d6bd1b-4afb-4f16-adde-= 8ee8b5ba1041%40isocpp.org.


--
Who=E2=80=99s got the sweetest disposition?
One guess, that=E2=80=99s w= ho?
Who=E2=80=99d never, ever start an argument?
Who never shows a bi= t of temperament?
Who's never wrong but always right?
Who'd n= ever dream of starting a fight?
Who get stuck with all the bad luck?

--
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-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/bacc5cd9-230a-4865-858c-78566502cfef= %40isocpp.org.
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