220 32572 <50267964-19d0-4bb2-ba27-f018b58b8aa8@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: ma.kalbfuss@web.de Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: relaxing rules for ternary operator. Allow incompatible types. Date: Mon, 22 May 2017 00:13:40 -0700 (PDT) Lines: 1003 Approved: news@gmane.org Message-ID: <50267964-19d0-4bb2-ba27-f018b58b8aa8@isocpp.org> References: <1b5ee8eb-53df-4e98-af2f-829c7bc2e5b2@isocpp.org> <1678895.0nQhqNqFQE@tjmaciei-mobl1> <1620864.HL4j5jKv18@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_2507_1148003169.1495437220471" X-Trace: blaine.gmane.org 1495437224 13281 195.159.176.226 (22 May 2017 07:13:44 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 22 May 2017 07:13:44 +0000 (UTC) Cc: ma.kalbfuss@web.de To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBC7YTI72XQOBBJM7RLEQKGQER5AZVRI@isocpp.org Mon May 22 09:13:39 2017 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 1dChX7-0003HS-Ec for gclcip-std-proposals@m.gmane.org; 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boundary="----=_Part_2508_366975323.1495437220473" ------=_Part_2508_366975323.1495437220473 Content-Type: text/plain; charset="UTF-8" struct W{ int doit(){ return 1; } }; struct X{ int doit(){ return 2; } }; struct Y{ int doit(){ return 3; } }; struct Z{ int doit(){ return 4; } }; int example(bool runtime_condition1, bool runtime_condition2) { int result; if(!runtime_condition1) goto ternary_branch_1; if(!runtime_condition2) goto ternary_branch_2; result = W{}.doit() + Y{}.doit(); goto ternary_end; ternary_branch_1: if(!runtime_condition2); goto ternary_branch_3; result = X{}.doit() + Y{}.doit(); goto ternary_end; ternary_branch_2: result = W{}.doit() + Z{}.doit(); goto ternary_end; ternary_branch_3: result = X{}.doit() + Z{}.doit(); ternary_end: return result; } With -O0 W::doit(): push rbp mov rbp, rsp mov QWORD PTR [rbp-8], rdi mov eax, 1 pop rbp ret X::doit(): push rbp mov rbp, rsp mov QWORD PTR [rbp-8], rdi mov eax, 2 pop rbp ret Y::doit(): push rbp mov rbp, rsp mov QWORD PTR [rbp-8], rdi mov eax, 3 pop rbp ret Z::doit(): push rbp mov rbp, rsp mov QWORD PTR [rbp-8], rdi mov eax, 4 pop rbp ret example(bool, bool): push rbp mov rbp, rsp push rbx sub rsp, 40 mov edx, edi mov eax, esi mov BYTE PTR [rbp-36], dl mov BYTE PTR [rbp-40], al movzx eax, BYTE PTR [rbp-36] xor eax, 1 test al, al jne .L19 movzx eax, BYTE PTR [rbp-40] xor eax, 1 test al, al jne .L20 lea rax, [rbp-28] mov rdi, rax call W::doit() mov ebx, eax lea rax, [rbp-27] mov rdi, rax call Y::doit() add eax, ebx mov DWORD PTR [rbp-20], eax jmp .L14 ..L19: nop nop lea rax, [rbp-22] mov rdi, rax call X::doit() mov ebx, eax lea rax, [rbp-21] mov rdi, rax call Z::doit() add eax, ebx mov DWORD PTR [rbp-20], eax jmp .L14 ..L20: nop lea rax, [rbp-24] mov rdi, rax call W::doit() mov ebx, eax lea rax, [rbp-23] mov rdi, rax call Z::doit() add eax, ebx mov DWORD PTR [rbp-20], eax nop ..L14: mov eax, DWORD PTR [rbp-20] add rsp, 40 pop rbx pop rbp ret With -O3 example(bool, bool): test dil, dil mov eax, 6 je .L1 xor eax, eax test sil, sil sete al add eax, 4 ..L1: rep ret Am Montag, 22. Mai 2017 08:33:33 UTC+2 schrieb ma.ka...@web.de: > > Sure, you don't have always exponential growth when using templates. But > if you simulating this case with template functions you end up having the > same problem. > So I wouldn't say, that this something completely new. It is the nature of > the problem we try to solve. You have either runtime overhad or exponential > growth. > Maybe there is a way to avoid exponential growth using optimization > techniques. Assumably in many cases the optimizer will reduce the amount of > code anyway. > There could be a guaranteed optimization. But I'm not sure which. I will > build up an example, where the code isn't completely optimized away. > > I assume variant is an untagged union? Let's try to minimise our examples. > > > Am Montag, 22. Mai 2017 02:12:20 UTC+2 schrieb Thiago Macieira: >> >> On domingo, 21 de maio de 2017 13:54:51 PDT ma.ka...@web.de wrote: >> > Yeah, i realize that. This is something you have to consider if you're >> > using templates extensively. >> >> No, it isn't. Today, the use of templates does not imply exponential >> growth of >> generated code. >> >> That is something completely new with your proposal. >> >> > This is not the right solution for everything. >> > I think in most cases, you use one or at most two ternary operators in >> one >> > place. For three or more ternary operators the runtime overhead is >> > assumably the lesser of two evils. But even if it grows exponentially, >> the >> > constants are pretty small. Normaly only a few instructions are >> involved. >> >> Not necessarily. Remember that you may not reevaluate the condition, so >> either >> this generates completely separate code paths (and thus the exponential >> expansion) or the result of the evaluation is stored in a hidden variable >> that >> is evaluated every time you access that automatic variable. >> >> That is, when you write: >> >> auto x = runtime_condition1 ? A{} : B{}; >> auto y = runtime_conditoin2 ? C{} : D{}; >> x.f(); >> >> This expands to either: >> >> if (runtime_condition1) { >> auto x = A{}; >> if (runtime_condition2) { >> auto y = C {}; >> x.f() + y.f(); >> } else { >> auto y = D {}; >> x.f() + y.f(); >> } >> } else { >> auto x = B{}; >> if (runtime_condition2) { >> auto y = C {}; >> x.f() + y.f(); >> } else { >> auto y = D {}; >> x.f() + y.f(); >> } >> } >> >> or to: >> >> variant x; >> variant y; >> bool hidden1 = runtime_condition1; >> if (hidden1) >> x.create(); >> else >> x.create(); >> bool hidden2 = runtime_condition2; >> if (hidden2) >> y.create(); >> else >> y.create(); >> if (hidden1) { >> if (hidden2) >> x.as().f() + y.as().f(); >> else >> x.as().f() + y.as().f(); >> } else { >> if (hidden2) >> x.as().f() + y.as().f(); >> else >> x.as().f() + y.as().f(); >> } >> >> -- >> Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org >> Software Architect - Intel Open Source Technology Center >> >> -- 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/50267964-19d0-4bb2-ba27-f018b58b8aa8%40isocpp.org. ------=_Part_2508_366975323.1495437220473 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
struct W{ int doit(){ return 1; } };
struct X{ int doi= t(){ return 2; } };
struct Y{ int doit(){ retu= rn = 3; } };
struct Z<= /span>{ int doit(){ return 4; } };


int example(bool runtime_condition1, = bool runti= me_condition2) {
=C2=A0 =C2=A0 int result;

=C2=A0 =C2=A0 if(!runtime_condition1)
=C2=A0 =C2=A0 =C2=A0 =C2=A0 <= span style=3D"color: #008;" class=3D"styled-by-prettify">goto ternary_branch_1= ;

=C2=A0 =C2=A0 if(!runtime_condition2)
=C2=A0 =C2=A0 =C2=A0 =C2= =A0 goto ternary_bra= nch_2;

=C2=A0= =C2=A0 result =3D W= {}.= doit() + Y{}.doit();=C2=A0 =C2=A0 goto= ternary_end;
=C2= =A0 =C2=A0
ternary_branch_1:

=C2=A0 =C2=A0 if(!runtime_condition2);
=C2=A0 =C2=A0 =C2=A0 =C2=A0 goto ternary_branch_3;

=C2=A0 =C2=A0 result =3D X{}.doit() +<= /span> Y{}.doit();
=C2=A0 =C2=A0 goto ternary_end;

ternary_branch_2:

=C2=A0 =C2=A0 result <= span style=3D"color: #660;" class=3D"styled-by-prettify">=3D W{}.doit() + Z{}.doit<= span style=3D"color: #660;" class=3D"styled-by-prettify">();
=C2=A0 =C2=A0 = goto ternary_end;

ternary_branch_3:

=C2=A0 =C2=A0 r= esult =3D<= /span> X{}.doit() + Z{}.doit();<= /span>

ter= nary_end:<= /span>
=C2=A0 = =C2=A0 ret= urn result= ;
}



With -O0
W::doit():
=C2=A0 = =C2=A0 =C2=A0 =C2=A0 push =C2=A0 =C2=A0rbp
=C2=A0 =C2=A0 =C2=A0 =C2=A0 m= ov =C2=A0 =C2=A0 rbp, rsp
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 QWORD PTR [rbp-8], rdi
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 eax, 1
=C2=A0 =C2=A0 =C2=A0 =C2=A0 pop = =C2=A0 =C2=A0 rbp
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ret
X::doit():
=C2=A0 =C2=A0 =C2=A0 =C2=A0 push =C2=A0 =C2= =A0rbp
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 rbp, rsp
=C2=A0 =C2=A0 =C2=A0 =C2=A0= mov =C2=A0 =C2=A0 QWORD PTR [rbp-8], rdi
=C2=A0 =C2=A0 = =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 eax, 2=C2=A0 =C2=A0 =C2=A0 =C2=A0 pop =C2=A0 =C2=A0 rbp
=C2=A0 =C2=A0 =C2=A0= =C2=A0 ret
Y::do= it():
=C2=A0 =C2= =A0 =C2=A0 =C2=A0 push =C2=A0 =C2=A0rbp
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov = =C2=A0 =C2=A0 rbp, r= sp
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 QWORD PTR [rbp-8], rdi
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 eax<= span style=3D"color: #660;" class=3D"styled-by-prettify">, 3
=C2=A0 =C2=A0 =C2=A0 =C2=A0 pop =C2=A0 = =C2=A0 rbp
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ret
Z::doit():
=C2=A0 =C2=A0 =C2=A0 =C2=A0 push =C2=A0 =C2=A0rbp=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 rbp, rsp
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2= =A0 =C2=A0 QWORD PTR [rbp-8], rdi
=C2=A0 =C2=A0 =C2=A0 = =C2=A0 mov =C2=A0 =C2=A0 eax, = 4
=C2= =A0 =C2=A0 =C2=A0 =C2=A0 pop =C2=A0 =C2=A0 rbp
=C2=A0 =C2=A0 =C2=A0 =C2= =A0 ret
example(b= ool, bool):
=C2=A0 =C2=A0 =C2=A0 =C2=A0 push = =C2=A0 =C2=A0rbp
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 rbp, rsp
=C2=A0 =C2=A0 =C2= =A0 =C2=A0 push =C2=A0 =C2=A0rbx
=C2=A0 =C2=A0 =C2=A0 =C2=A0 sub =C2=A0 =C2=A0 rsp, 40
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 = =C2=A0 edx= , edi
= =C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 eax, esi
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2= =A0 =C2=A0 BYTE PTR [rbp-36], dl
=C2=A0 =C2=A0 =C2=A0 =C2= =A0 mov =C2=A0 =C2=A0 BYTE PTR [rbp-40], al
=C2=A0 =C2=A0= =C2=A0 =C2=A0 movzx =C2=A0 eax, BYTE PTR [rbp-36]
=C2=A0 =C2=A0 =C2=A0 =C2= =A0 xor =C2=A0 =C2=A0 eax, 1
=C2=A0 = =C2=A0 =C2=A0 =C2=A0 test =C2=A0 =C2=A0al, al
=C2=A0 =C2=A0 =C2=A0 =C2=A0 jne =C2=A0 =C2= =A0 .L19
=C2=A0 = =C2=A0 =C2=A0 =C2=A0 movzx =C2=A0 eax, BYTE PTR [rbp-40]
=C2=A0 =C2=A0 =C2=A0= =C2=A0 xor =C2=A0 =C2=A0 eax, 1
=C2= =A0 =C2=A0 =C2=A0 =C2=A0 test =C2=A0 =C2=A0al, al
=C2=A0 =C2=A0 =C2=A0 =C2=A0 jne =C2=A0 =C2= =A0 .L20
=C2=A0 = =C2=A0 =C2=A0 =C2=A0 lea =C2=A0 =C2=A0 rax, [rbp-= 28<= span style=3D"color: #660;" class=3D"styled-by-prettify">]
=C2=A0 =C2=A0 =C2=A0 = =C2=A0 mov =C2=A0 =C2=A0 rdi, rax
=C2=A0 =C2=A0 =C2=A0 =C2=A0 call =C2=A0 =C2=A0W::doit()
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0= =C2=A0 ebx, eax
= =C2=A0 =C2=A0 =C2=A0 =C2=A0 lea =C2=A0 =C2=A0 rax, [rbp-27]
=C2=A0 =C2=A0 =C2= =A0 =C2=A0 mov =C2=A0 =C2=A0 rdi, rax
=C2=A0 =C2=A0 =C2=A0 =C2=A0 call =C2=A0 =C2=A0Y::doit()
=C2=A0 =C2=A0 =C2=A0 =C2=A0 add = =C2=A0 =C2=A0 eax, e= bx
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 DWORD PTR [rbp-20], eax
=C2=A0 =C2=A0 =C2=A0 =C2=A0 jmp =C2=A0 =C2=A0 .L14
.L19:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 nop
=C2=A0 =C2=A0 =C2= =A0 =C2=A0 nop
=C2=A0 =C2=A0 =C2=A0 =C2=A0 lea =C2=A0 =C2=A0 rax<= span style=3D"color: #660;" class=3D"styled-by-prettify">, [rbp-22]=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 rdi, rax
=C2=A0 =C2=A0 =C2=A0 =C2=A0 call = =C2=A0 =C2=A0X::doit= ()<= span style=3D"color: #000;" class=3D"styled-by-prettify">
=C2=A0 =C2=A0 = =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 ebx, eax
=C2=A0 =C2=A0 =C2=A0 =C2=A0 lea =C2=A0 =C2=A0 rax, [rbp-21]
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 rdi, rax
=C2=A0 =C2=A0 =C2=A0 =C2= =A0 call =C2=A0 =C2=A0Z::doit(= )
=C2= =A0 =C2=A0 =C2=A0 =C2=A0 add =C2=A0 =C2=A0 eax, ebx
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 = =C2=A0 DWORD PTR [rb= p-<= span style=3D"color: #066;" class=3D"styled-by-prettify">20], eax
=C2=A0 =C2=A0 =C2=A0 =C2= =A0 jmp =C2=A0 =C2=A0 .L14
= ..L20:
=C2=A0 =C2=A0 =C2=A0 = =C2=A0 nop
=C2=A0 =C2=A0 =C2=A0 =C2=A0 lea =C2=A0 =C2=A0 rax, [rbp-24]
=C2= =A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 rdi, rax
=C2=A0 =C2=A0 =C2=A0 =C2=A0 call =C2=A0 = =C2=A0W::<= /span>doit= ()
=C2=A0 =C2=A0 =C2=A0 = =C2=A0 mov =C2=A0 =C2=A0 ebx, eax
=C2=A0 =C2=A0 =C2=A0 =C2=A0 lea =C2=A0 =C2=A0 rax, [rbp-23]=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 rdi, rax
=C2=A0 =C2=A0 =C2=A0 =C2=A0 call = =C2=A0 =C2=A0Z::doit= ()<= span style=3D"color: #000;" class=3D"styled-by-prettify">
=C2=A0 =C2=A0 = =C2=A0 =C2=A0 add =C2=A0 =C2=A0 eax, ebx
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 DWORD= PTR [rbp-20], eax
=C2=A0 =C2=A0 =C2=A0 =C2=A0 nop
<= /span>.L14:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 mov = =C2=A0 =C2=A0 eax, D= WORD PTR [= rbp= -20]
=C2=A0 =C2=A0 =C2=A0 =C2=A0 add =C2=A0 = =C2=A0 rsp= , <= span style=3D"color: #066;" class=3D"styled-by-prettify">40
=C2=A0 =C2=A0 =C2=A0 = =C2=A0 pop =C2=A0 =C2=A0 rbx
=C2=A0 =C2=A0 =C2=A0 =C2=A0 pop =C2=A0 =C2= =A0 rbp
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ret

Wit= h -O3

example(bool, bool):
=C2=A0 =C2=A0 =C2=A0 =C2=A0 test =C2=A0 = =C2=A0dil,= dil
= =C2=A0 =C2=A0 =C2=A0 =C2=A0 mov =C2=A0 =C2=A0 eax, 6
=C2=A0 =C2=A0 =C2=A0 =C2=A0 je =C2=A0 =C2=A0 =C2=A0<= span style=3D"color: #660;" class=3D"styled-by-prettify">.L1
=C2=A0 =C2=A0 =C2=A0 = =C2=A0 xor =C2=A0 =C2=A0 eax, eax
=C2=A0 =C2=A0 =C2=A0 =C2=A0 test =C2=A0 =C2=A0sil, sil
=C2=A0 =C2=A0 =C2=A0= =C2=A0 sete =C2=A0 =C2=A0al
=C2=A0 =C2=A0 =C2=A0 =C2=A0 add =C2=A0 =C2= =A0 eax, 4
.L1:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 rep ret
<= /div>




Am Montag, 22. Mai 2017 08:33:33 UTC+2 schrieb ma.= ka...@web.de:
= Sure, you don't have always exponential growth when using templates. Bu= t if you simulating this case with template functions you end up having the= same problem.
So I wouldn't say, that this something completely new= .. It is the nature of the problem we try to solve. You have either runtime = overhad or exponential growth.
Maybe there is a way to avoid exponential= growth using optimization techniques. Assumably in many cases the optimize= r will reduce the amount of code anyway.
There could be a guaranteed opt= imization. But I'm not sure which. I will build up an example, where th= e code isn't completely optimized away.

I assume variant is an u= ntagged union? Let's try to minimise our examples.


Am Montag= , 22. Mai 2017 02:12:20 UTC+2 schrieb Thiago Macieira:
On domingo, 21 de maio de 2017 13:54:51 PDT ma.ka...@web.de wrote:
> Yeah, i realize that. This is something you have to consider if yo= u're
> using templates extensively.=20

No, it isn't. Today, the use of templates does not imply exponentia= l growth of=20
generated code.

That is something completely new with your proposal.

> This is not the right solution for everything.
> I think in most cases, you use one or at most two ternary operator= s in one
> place. For three or more ternary operators the runtime overhead is
> assumably the lesser of two evils. But even if it grows exponentia= lly, the
> constants are pretty small. Normaly only a few instructions are in= volved.

Not necessarily. Remember that you may not reevaluate the condition, so= either=20
this generates completely separate code paths (and thus the exponential= =20
expansion) or the result of the evaluation is stored in a hidden variab= le that=20
is evaluated every time you access that automatic variable.=20

That is, when you write:

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0auto x =3D runtime_cond= ition1 ? A{} : B{};=20
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0auto y =3D runtime_cond= itoin2 ? C{} : D{};
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0x.f();

This expands to either:

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (runtime_condition1)= {
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0auto x =3D A{};
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0if (runtime_condition2) {
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= auto y =3D C {};
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= x.f() + y.f();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0} else {
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= auto y =3D D {};
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= x.f() + y.f();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0}
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0} else {
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0auto x =3D B{};
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0if (runtime_condition2) {
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= auto y =3D C {};
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= x.f() + y.f();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0} else {
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= auto y =3D D {};
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= x.f() + y.f();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0}
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0}

or to:

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0variant<A, B> x;
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0variant<C, D> y;
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0bool hidden1 =3D runtim= e_condition1;
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (hidden1)
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0x.create<A>();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0else
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0x.create<B>();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0bool hidden2 =3D runtim= e_condition2;
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (hidden2)
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0y.create<C>();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0else
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0y.create<D>();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (hidden1) {
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0if (hidden2)
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= x.as<A>().f() + y.as= <C>().f();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0else
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= x.as<A>().f() + y.as= <D>().f();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0} else {
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0if (hidden2)
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= x.as<B>().f() + y.as= <C>().f();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0else
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= x.as<B>().f() + y.as= <D>().f();
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0}

--=20
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
=C2=A0 =C2=A0Software Architect - Intel Open Source Technology Center

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------=_Part_2508_366975323.1495437220473-- ------=_Part_2507_1148003169.1495437220471-- .