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On 24 April 2013 13:55, <rob.desbois@gmail.com> wrote:

> As far as I can tell from the wording of N3649, perfect forwarding is not
> currently possible via generic lambdas, as the invented type
> template-parameter names are not accessible:
>
>     // utterly contrived example
>     template< class T >
>     auto make_factory() // using N3638 return type deduction
>     {
>         return []( auto&&... args ) {
>             return std::unique_ptr<T>( new T( std::forward<???>(args)...
> ));
>         }
>     }
>
> Am I correct in this conclusion?
> If so I'm guessing this wasn't merely an oversight, and is the reason just
> practicality of exposing the invented parameter names?
>
>
>
std::forward<decltype(args)...> or some such?

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><br><div class=3D"gmail=
_quote">On 24 April 2013 13:55,  <span dir=3D"ltr">&lt;<a href=3D"mailto:ro=
b.desbois@gmail.com" target=3D"_blank">rob.desbois@gmail.com</a>&gt;</span>=
 wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">As far as I can tell from the wording of N36=
49, perfect forwarding is not currently possible via generic lambdas, as th=
e invented type template-parameter names are not accessible:<div>
<br></div><div>=A0 =A0 // utterly contrived example</div><div>=A0 =A0 templ=
ate&lt; class T &gt;</div><div>=A0 =A0 auto make_factory() // using N3638 r=
eturn type deduction</div><div>=A0 =A0 {</div><div>=A0 =A0 =A0 =A0 return [=
]( auto&amp;&amp;... args ) {</div>
<div>=A0 =A0 =A0 =A0 =A0 =A0 return std::unique_ptr&lt;T&gt;( new T( std::f=
orward&lt;???&gt;(args)... ));</div><div>=A0 =A0 =A0 =A0 }</div><div>=A0 =
=A0 }</div><div><br></div><div>Am I correct in this conclusion?</div><div>I=
f so I&#39;m guessing this wasn&#39;t merely an oversight, and is the reaso=
n just practicality of exposing the invented parameter names?</div>
<div><br><br></div></blockquote><div><br></div><div>std::forward&lt;decltyp=
e(args)...&gt; or some such? <br></div></div><br></div></div>

<p></p>

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.

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On 24 April 2013 14:01, Ville Voutilainen <ville.voutilainen@gmail.com>wrote:

>
>
>
> On 24 April 2013 13:55, <rob.desbois@gmail.com> wrote:
>
>> As far as I can tell from the wording of N3649, perfect forwarding is not
>> currently possible via generic lambdas, as the invented type
>> template-parameter names are not accessible:
>>
>>     // utterly contrived example
>>     template< class T >
>>     auto make_factory() // using N3638 return type deduction
>>     {
>>         return []( auto&&... args ) {
>>             return std::unique_ptr<T>( new T( std::forward<???>(args)...
>> ));
>>         }
>>     }
>>
>> Am I correct in this conclusion?
>> If so I'm guessing this wasn't merely an oversight, and is the reason
>> just practicality of exposing the invented parameter names?
>>
>>
>>
> std::forward<decltype(args)...> or some such?
>
>
Ah, the accursed ellipsis and where to put it.
std::forward<decltype(args)>(args)... seems to do it.

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><br><div class=3D"gmail=
_quote">On 24 April 2013 14:01, Ville Voutilainen <span dir=3D"ltr">&lt;<a =
href=3D"mailto:ville.voutilainen@gmail.com" target=3D"_blank">ville.voutila=
inen@gmail.com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div dir=3D"ltr"><br><div class=3D"gmail_ext=
ra"><br><br><div class=3D"gmail_quote"><div class=3D"im">On 24 April 2013 1=
3:55,  <span dir=3D"ltr">&lt;<a href=3D"mailto:rob.desbois@gmail.com" targe=
t=3D"_blank">rob.desbois@gmail.com</a>&gt;</span> wrote:<br>

<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">As far as I can tell from the wording of N36=
49, perfect forwarding is not currently possible via generic lambdas, as th=
e invented type template-parameter names are not accessible:<div>

<br></div><div>=A0 =A0 // utterly contrived example</div><div>=A0 =A0 templ=
ate&lt; class T &gt;</div><div>=A0 =A0 auto make_factory() // using N3638 r=
eturn type deduction</div><div>=A0 =A0 {</div><div>=A0 =A0 =A0 =A0 return [=
]( auto&amp;&amp;... args ) {</div>

<div>=A0 =A0 =A0 =A0 =A0 =A0 return std::unique_ptr&lt;T&gt;( new T( std::f=
orward&lt;???&gt;(args)... ));</div><div>=A0 =A0 =A0 =A0 }</div><div>=A0 =
=A0 }</div><div><br></div><div>Am I correct in this conclusion?</div><div>I=
f so I&#39;m guessing this wasn&#39;t merely an oversight, and is the reaso=
n just practicality of exposing the invented parameter names?</div>

<div><br><br></div></blockquote><div><br></div></div><div>std::forward&lt;d=
ecltype(args)...&gt; or some such? <br></div></div><br></div></div>
</blockquote></div><br></div><div class=3D"gmail_extra">Ah, the accursed el=
lipsis and where to put it. std::forward&lt;decltype(args)&gt;(args)... see=
ms to do it.<br></div></div>

<p></p>

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--089e01229c30963b2a04db194445--

.

2013/4/24 Ville Voutilainen <ville.voutilainen@gmail.com>:
>
> On 24 April 2013 13:55, <rob.desbois@gmail.com> wrote:
>>
>> As far as I can tell from the wording of N3649, perfect forwarding is not
>> currently possible via generic lambdas, as the invented type
>> template-parameter names are not accessible:
>>
>>     // utterly contrived example
>>     template< class T >
>>     auto make_factory() // using N3638 return type deduction
>>     {
>>         return []( auto&&... args ) {
>>             return std::unique_ptr<T>( new T( std::forward<???>(args)...
>> ));
>>         }
>>     }
>>
>> Am I correct in this conclusion?
>> If so I'm guessing this wasn't merely an oversight, and is the reason just
>> practicality of exposing the invented parameter names?
>>
>>
> std::forward<decltype(args)...> or some such?

I think this the wrong answer here, because every args is an lvalue in
this context and therefore the decltype() deduction returns an
lvalue-reference.

- Daniel

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>
>
> I think this the wrong answer here, because every args is an lvalue in
> this context and therefore the decltype() deduction returns an
> lvalue-reference.
>
>
When used with identifiers, decltype returns the type they were declared
with.

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<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="im">
<br>
</div>I think this the wrong answer here, because every args is an lvalue in<br>
this context and therefore the decltype() deduction returns an<br>
lvalue-reference.<br>
<span class=""><font color="#888888"></font></span><br></blockquote></div><br>When used with identifiers, decltype returns the type they were declared with.<br></div></div>

<p></p>

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--14dae9d70e6e7a794a04db194bef--

.

2013/4/24 Martinho Fernandes <martinho.fernandes@gmail.com>:
>>
>> I think this the wrong answer here, because every args is an lvalue in
>> this context and therefore the decltype() deduction returns an
>> lvalue-reference.
>>
>
> When used with identifiers, decltype returns the type they were declared
> with.

Yes, you are right, I was on the wrong track here.

- Daniel

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On Wed, Apr 24, 2013 at 6:13 AM, Daniel Kr=FCgler
<daniel.kruegler@gmail.com>wrote:

> 2013/4/24 Martinho Fernandes <martinho.fernandes@gmail.com>:
> >>
> >> I think this the wrong answer here, because every args is an lvalue in
> >> this context and therefore the decltype() deduction returns an
> >> lvalue-reference.
> >>
> >
> > When used with identifiers, decltype returns the type they were declare=
d
> > with.
>
> Yes, you are right, I was on the wrong track here.
>

As was I, until Ville and Doug showed me the error of my ways  (while
discussing this in EWG).

--=20

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><div class=3D"gmail_quote">=
On Wed, Apr 24, 2013 at 6:13 AM, Daniel Kr=FCgler <span dir=3D"ltr">&lt;<a =
href=3D"mailto:daniel.kruegler@gmail.com" target=3D"_blank">daniel.kruegler=
@gmail.com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">2013/4/24 Martinho Fernandes &lt;<a href=3D"=
mailto:martinho.fernandes@gmail.com">martinho.fernandes@gmail.com</a>&gt;:<=
br>

<div class=3D"im">&gt;&gt;<br>
&gt;&gt; I think this the wrong answer here, because every args is an lvalu=
e in<br>
&gt;&gt; this context and therefore the decltype() deduction returns an<br>
&gt;&gt; lvalue-reference.<br>
&gt;&gt;<br>
&gt;<br>
&gt; When used with identifiers, decltype returns the type they were declar=
ed<br>
&gt; with.<br>
<br>
</div>Yes, you are right, I was on the wrong track here.<br>
<span class=3D"HOEnZb"></span></blockquote><div><br></div><div>As was I, un=
til Ville and Doug showed me the error of my ways=A0 (while discussing this=
 in EWG).<br>=A0<br></div></div></div></div>

<p></p>

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--047d7b47274832880604db19b8ec
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On 24 April 2013 14:23, Faisal Vali <faisalv@gmail.com> wrote:

> As was I, until Ville and Doug showed me the error of my ways  (while
> discussing this in EWG).
>

I thought the decltype works, but didn't think of any lvalueness issues.
Doug clarified that it
actually works correctly. ;)

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><br><div class=3D"gmail=
_quote">On 24 April 2013 14:23, Faisal Vali <span dir=3D"ltr">&lt;<a href=
=3D"mailto:faisalv@gmail.com" target=3D"_blank">faisalv@gmail.com</a>&gt;</=
span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div dir=3D"ltr">As was I, until Ville and D=
oug showed me the error of my ways=A0 (while discussing this in EWG).<br></=
div>
</blockquote><div><br></div><div>I thought the decltype works, but didn&#39=
;t think of any lvalueness issues. Doug clarified that it<br>actually works=
 correctly. ;)<br></div></div><br></div></div>

<p></p>

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On Wednesday, April 24, 2013 3:01:59 PM UTC+4, Ville Voutilainen wrote:
>
> std::forward<decltype(args)...> or some such?
>

Some people (like me) already prefer to use FORWARD(arg) instead of verbose
notation std::forward<Arg>(arg). In most cases

    #define FORWARD(x) static_cast<decltype(x) &&>(x)

provides desirable semantics.

std::forward is helpful when we need a conversion to some specific type
that is not deducible from argument, and, IMO, there is no point to use it
otherwise.
..

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On Wednesday, April 24, 2013 3:01:59 PM UTC+4, Ville Voutilainen wrote:<blo=
ckquote class=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;border-=
left: 1px #ccc solid;padding-left: 1ex;"><div dir=3D"ltr"><div>std::forward=
&lt;decltype(args)...<wbr>&gt; or some such? <br></div></div></blockquote><=
div><br>Some people (like me) already prefer to use FORWARD(arg) instead of=
 verbose notation std::forward&lt;Arg&gt;(arg). In most cases<br><br>&nbsp;=
&nbsp;&nbsp; #define FORWARD(x) static_cast&lt;decltype(x) &amp;&amp;&gt;(x=
)<br><br>provides desirable semantics.<br><br>std::forward is helpful when =
we need a conversion to some specific type that is not deducible from argum=
ent, and, IMO, there is no point to use it otherwise.<br>.<br></div>

<p></p>

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--001a11c2ab98b8e6ea04db1af066
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On 24 April 2013 15:36, Nikolay Ivchenkov <mk.ivchenkov@gmail.com> wrote:

> On Wednesday, April 24, 2013 3:01:59 PM UTC+4, Ville Voutilainen wrote:
>>
>> std::forward<decltype(args)...**> or some such?
>>
>
> Some people (like me) already prefer to use FORWARD(arg) instead of
> verbose notation std::forward<Arg>(arg). In most cases
>
>     #define FORWARD(x) static_cast<decltype(x) &&>(x)
>
> provides desirable semantics.
>
> std::forward is helpful when we need a conversion to some specific type
> that is not deducible from argument, and, IMO, there is no point to use it
> otherwise.
>
>
Perhaps we should standardize such a utility.

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><br><div class=3D"gmail=
_quote">On 24 April 2013 15:36, Nikolay Ivchenkov <span dir=3D"ltr">&lt;<a =
href=3D"mailto:mk.ivchenkov@gmail.com" target=3D"_blank">mk.ivchenkov@gmail=
..com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div class=3D"im">On Wednesday, April 24, 20=
13 3:01:59 PM UTC+4, Ville Voutilainen wrote:<blockquote class=3D"gmail_quo=
te" style=3D"margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-=
left:1ex">
<div dir=3D"ltr"><div>std::forward&lt;decltype(args)...<u></u>&gt; or some =
such? <br></div></div></blockquote></div><div><br>Some people (like me) alr=
eady prefer to use FORWARD(arg) instead of verbose notation std::forward&lt=
;Arg&gt;(arg). In most cases<br>
<br>=A0=A0=A0 #define FORWARD(x) static_cast&lt;decltype(x) &amp;&amp;&gt;(=
x)<br><br>provides desirable semantics.<br><br>std::forward is helpful when=
 we need a conversion to some specific type that is not deducible from argu=
ment, and, IMO, there is no point to use it otherwise.<br>
<br></div></blockquote><div><br></div><div>Perhaps we should standardize su=
ch a utility. <br></div></div><br></div></div>

<p></p>

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&nbsp;<br />
&nbsp;<br />

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A macro? I don't think that would be a good idea. And it can't be
implemented without a macro, as you can't just take *only* the function
argument, like, say `std::better_forward(x)` - how would `better_forward`
know the original value category?

On Wednesday, April 24, 2013 3:04:20 PM UTC+2, Ville Voutilainen wrote:
>
>
>
>
> On 24 April 2013 15:36, Nikolay Ivchenkov <mk.ivc...@gmail.com<javascript:>
> > wrote:
>
>> On Wednesday, April 24, 2013 3:01:59 PM UTC+4, Ville Voutilainen wrote:
>>>
>>> std::forward<decltype(args)...**> or some such?
>>>
>>
>> Some people (like me) already prefer to use FORWARD(arg) instead of
>> verbose notation std::forward<Arg>(arg). In most cases
>>
>>     #define FORWARD(x) static_cast<decltype(x) &&>(x)
>>
>> provides desirable semantics.
>>
>> std::forward is helpful when we need a conversion to some specific type
>> that is not deducible from argument, and, IMO, there is no point to use it
>> otherwise.
>>
>>
> Perhaps we should standardize such a utility.
>
>

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A macro? I don't think that would be a good idea. And it can't be implement=
ed without a macro, as you can't just take *only* the function argument, li=
ke, say `std::better_forward(x)` - how would `better_forward` know the orig=
inal value category?<br><br>On Wednesday, April 24, 2013 3:04:20 PM UTC+2, =
Ville Voutilainen wrote:<blockquote class=3D"gmail_quote" style=3D"margin: =
0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;"><div d=
ir=3D"ltr"><br><div><br><br><div class=3D"gmail_quote">On 24 April 2013 15:=
36, Nikolay Ivchenkov <span dir=3D"ltr">&lt;<a href=3D"javascript:" target=
=3D"_blank" gdf-obfuscated-mailto=3D"6oO5yZ8Cb-YJ">mk.ivc...@gmail.com</a>&=
gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div>On Wednesday, April 24, 2013 3:01:59 PM=
 UTC+4, Ville Voutilainen wrote:<blockquote class=3D"gmail_quote" style=3D"=
margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir=3D"ltr"><div>std::forward&lt;decltype(args)...<u></u><wbr>&gt; or =
some such? <br></div></div></blockquote></div><div><br>Some people (like me=
) already prefer to use FORWARD(arg) instead of verbose notation std::forwa=
rd&lt;Arg&gt;(arg). In most cases<br>
<br>&nbsp;&nbsp;&nbsp; #define FORWARD(x) static_cast&lt;decltype(x) &amp;&=
amp;&gt;(x)<br><br>provides desirable semantics.<br><br>std::forward is hel=
pful when we need a conversion to some specific type that is not deducible =
from argument, and, IMO, there is no point to use it otherwise.<br>
<br></div></blockquote><div><br></div><div>Perhaps we should standardize su=
ch a utility. <br></div></div><br></div></div>
</blockquote>

<p></p>

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On 24 April 2013 16:06, Xeo <hivemaster@hotmail.de> wrote:

> A macro? I don't think that would be a good idea. And it can't be
> implemented without a macro, as you can't just take *only* the


See the "such a" part in what I wrote.


> function argument, like, say `std::better_forward(x)` - how would
> `better_forward` know the original value category?
>
>
Perhaps it can't, if we would be talking about a certain kind of
implementation, rather than the semantics
of what the utility does. Perhaps it needs to be an
implementation-supported utility rather than a pure library.

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><br><div class=3D"gmail=
_quote">On 24 April 2013 16:06, Xeo <span dir=3D"ltr">&lt;<a href=3D"mailto=
:hivemaster@hotmail.de" target=3D"_blank">hivemaster@hotmail.de</a>&gt;</sp=
an> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">A macro? I don&#39;t think that would be a g=
ood idea. And it can&#39;t be implemented without a macro, as you can&#39;t=
 just take *only* the </blockquote>
<div><br></div><div>See the &quot;such a&quot; part in what I wrote.<br>=A0=
<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;bord=
er-left:1px #ccc solid;padding-left:1ex">function argument, like, say `std:=
:better_forward(x)` - how would `better_forward` know the original value ca=
tegory?<br>
<br></blockquote><div><br></div><div>Perhaps it can&#39;t, if we would be t=
alking about a certain kind of implementation, rather than the semantics<br=
>of what the utility does. Perhaps it needs to be an implementation-support=
ed utility rather than a pure library. <br>
</div></div><br></div></div>

<p></p>

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On Wednesday, April 24, 2013 6:06:48 AM UTC-7, Xeo wrote:
>
> A macro? I don't think that would be a good idea.


C++ has plenty of standard macros. I'm not in favor of standardizing this
one (though I prefer that to the suggestion of an explicit language
intrinsic or something), but the fact that it's a macro shouldn't be
considered sufficient reasoning to not standardize it.

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On Wednesday, April 24, 2013 6:06:48 AM UTC-7, Xeo wrote:<blockquote class=
=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;border-left: 1px #cc=
c solid;padding-left: 1ex;">A macro? I don't think that would be a good ide=
a.</blockquote><div><br>C++ has plenty of standard macros. I'm not in favor=
 of standardizing this one (though I prefer that to the suggestion of an ex=
plicit language intrinsic or something), but the fact that it's a macro sho=
uldn't be considered sufficient reasoning to not standardize it.</div><br>

<p></p>

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On Wednesday, 24 April 2013 12:23:13 UTC+1, faisalv wrote:

>
> On Wed, Apr 24, 2013 at 6:13 AM, Daniel Kr=FCgler <daniel....@gmail.com<j=
avascript:>
> > wrote:
>
>> > When used with identifiers, decltype returns the type they were declar=
ed
>> > with.
>>
>> Yes, you are right, I was on the wrong track here.
>>
>
> As was I, until Ville and Doug showed me the error of my ways  (while=20
> discussing this in EWG).
> =20
>

I think that is exactly what had me confused too
Ville's 2nd proposed syntax looks like it'll do the trick.

Thanks all :-)
--rob

--=20

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On Wednesday, 24 April 2013 12:23:13 UTC+1, faisalv  wrote:<br><blockquote =
class=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;border-left: 1p=
x #ccc solid;padding-left: 1ex;"><div dir=3D"ltr"><br><div><div class=3D"gm=
ail_quote">On Wed, Apr 24, 2013 at 6:13 AM, Daniel Kr=FCgler <span dir=3D"l=
tr">&lt;<a href=3D"javascript:" target=3D"_blank" gdf-obfuscated-mailto=3D"=
puoLx3TuNPUJ">daniel....@gmail.com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div>&gt; When used with identifiers, declty=
pe returns the type they were declared<br>
&gt; with.<br>
<br>
</div>Yes, you are right, I was on the wrong track here.<br>
<span></span></blockquote><div><br></div><div>As was I, until Ville and Dou=
g showed me the error of my ways&nbsp; (while discussing this in EWG).<br>&=
nbsp;<br></div></div></div></div></blockquote><div><br></div><div>I think t=
hat is exactly what had me confused too</div><div>Ville's 2nd proposed synt=
ax looks like it'll do the trick.</div><div><br></div><div>Thanks all :-)</=
div><div>--rob</div>

<p></p>

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Since there was initial confusion here on my part, I included the following
example in the wording (N3649) to illustrate the use of std::forward with
variadic auto:

 [ Example:
    auto glambda  =3D [](auto a, auto&& b) { return  a < b; };
  bool b =3D glambda(3, 3.14);       // OK
  auto vglambda =3D [](auto printer) {
     return [=3D](auto&& ... ts) {   // OK: ts is a  function parameter pac=
k
         printer(std::forward<decltype(ts)>(ts)...);  //<-- NOTE this line
         return [=3D]() {
           printer(ts ...);
         };
     };
  };

  auto p =3D vglambda( [](auto v1, auto v2, auto v3)
                         { std::cout << v1 << v2 << v3; } );
  auto q =3D p(1, 'a', 3.14);  // OK: outputs 1a3.14
  q();                       // OK: outputs 1a3.14
=97 end example]

Faisal Vali



On Wed, Apr 24, 2013 at 9:41 AM, <rob.desbois@gmail.com> wrote:

> On Wednesday, 24 April 2013 12:23:13 UTC+1, faisalv wrote:
>
>
>> On Wed, Apr 24, 2013 at 6:13 AM, Daniel Kr=FCgler <daniel....@gmail.com>=
wrote:
>>
>>> > When used with identifiers, decltype returns the type they were
>>> declared
>>> > with.
>>>
>>> Yes, you are right, I was on the wrong track here.
>>>
>>
>> As was I, until Ville and Doug showed me the error of my ways  (while
>> discussing this in EWG).
>>
>>
>
> I think that is exactly what had me confused too
> Ville's 2nd proposed syntax looks like it'll do the trick.
>
> Thanks all :-)
> --rob
>

--=20

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--14dae9340445553c7e04db1cb999
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<div dir=3D"ltr">Since there was initial confusion here on my part, I inclu=
ded the following example in the wording (N3649) to illustrate the use of s=
td::forward with variadic auto:<br><br>=A0[ Example:<br>=A0=A0=A0 auto glam=
bda=A0 =3D [](auto a, auto&amp;&amp; b) { return=A0 a &lt; b; };<br>
=A0 bool b =3D glambda(3, 3.14);=A0=A0=A0=A0=A0=A0 // OK<br>=A0 auto vglamb=
da =3D [](auto printer) {<br>=A0=A0=A0=A0 return [=3D](auto&amp;&amp; ... t=
s) {=A0=A0 // OK: ts is a=A0 function parameter pack<br>=A0=A0=A0=A0=A0=A0=
=A0=A0 printer(std::forward&lt;decltype(ts)&gt;(ts)...);=A0 //&lt;-- NOTE t=
his line<br>
=A0=A0=A0=A0=A0=A0=A0=A0 return [=3D]() {<br>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
 printer(ts ...);<br>=A0=A0=A0=A0=A0=A0=A0=A0 };<br>=A0=A0=A0=A0 };<br>=A0 =
};<br><br>=A0 auto p =3D vglambda( [](auto v1, auto v2, auto v3)=A0=A0=A0 <=
br>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
 { std::cout &lt;&lt; v1 &lt;&lt; v2 &lt;&lt; v3; } );<br>
=A0 auto q =3D p(1, &#39;a&#39;, 3.14);=A0 // OK: outputs 1a3.14<br>=A0 q()=
;=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 // OK: =
outputs 1a3.14<br>=97 end example]<br></div><div class=3D"gmail_extra"><br =
clear=3D"all"><div>Faisal Vali<br><br></div>
<br><br><div class=3D"gmail_quote">On Wed, Apr 24, 2013 at 9:41 AM,  <span =
dir=3D"ltr">&lt;<a href=3D"mailto:rob.desbois@gmail.com" target=3D"_blank">=
rob.desbois@gmail.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_q=
uote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1e=
x">
On Wednesday, 24 April 2013 12:23:13 UTC+1, faisalv  wrote:<div class=3D"im=
"><br><blockquote class=3D"gmail_quote" style=3D"margin:0;margin-left:0.8ex=
;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr"><br><div><di=
v class=3D"gmail_quote">
On Wed, Apr 24, 2013 at 6:13 AM, Daniel Kr=FCgler <span dir=3D"ltr">&lt;<a>=
daniel....@gmail.com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div>&gt; When used with identifiers, declty=
pe returns the type they were declared<br>
&gt; with.<br>
<br>
</div>Yes, you are right, I was on the wrong track here.<br>
<span></span></blockquote><div><br></div><div>As was I, until Ville and Dou=
g showed me the error of my ways=A0 (while discussing this in EWG).<br>=A0<=
br></div></div></div></div></blockquote><div><br></div></div><div>I think t=
hat is exactly what had me confused too</div>
<div>Ville&#39;s 2nd proposed syntax looks like it&#39;ll do the trick.</di=
v><div><br></div><div>Thanks all :-)</div><div>--rob</div></blockquote></di=
v><br></div>

<p></p>

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On Wednesday, 24 April 2013 16:12:01 UTC+1, faisalv wrote:

> Since there was initial confusion here on my part, I included the
> following example in the wording (N3649) to illustrate the use of
> std::forward with variadic auto:
>

Ouch, had to show me up for missing it in the paper didn't you ;-)

Thanks for the pointer -- Rob

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On Wednesday, 24 April 2013 16:12:01 UTC+1, faisalv  wrote:<br><blockquote =
class=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;border-left: 1p=
x #ccc solid;padding-left: 1ex;"><div dir=3D"ltr">Since there was initial c=
onfusion here on my part, I included the following example in the wording (=
N3649) to illustrate the use of std::forward with variadic auto:</div></blo=
ckquote><div>&nbsp;</div><div>Ouch, had to show me up for missing it in the=
 paper didn't you ;-)</div><div><br></div><div>Thanks for the pointer -- Ro=
b</div>

<p></p>

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