220 8430 <e96c896b-7f74-49ac-9967-a1a31c5b223e@isocpp.org> article
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From: inkwizytoryankes@gmail.com
Newsgroups: gmane.comp.lang.c++.isocpp.proposals
Subject: Re: A new keyword for either a type or a variable
 (typical use case for variadic template template)?
Date: Tue, 7 Jan 2014 12:05:33 -0800 (PST)
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How it would help? `template <class...> class Template` still cant accept `
std::array<class,int>`.

On Tuesday, January 7, 2014 7:55:40 AM UTC+1, hun.nem...@gmail.com wrote:
>
> I think compile time reflection can handle this case.
> Based on this paper (
> https://github.com/hun-nemethpeter/cpp-reflector-mini/blob/master/Proposal.md
> ),
> the result will be similar to this:
>
>
> // driver
> struct SpecializationDriver
> {
>     constexpr SpecializationDriver(const meta::template_template_decl&templateTemplateDecl
> , 
>                                    const meta::template_decl& templateDecl
> )
>       : result(templateTemplateDecl.getName() == templateDecl.getName()) { 
> }
>     constexpr bool result;
> };
>
> template<template <class...> class Template, class T> $use(
> SpecializationDriver driver)
> bool is_specialization_of()
> {
>    return driver.result;
> }
>
> int main()
> {
>     std::cout<< is_specialization_of<std::tuple,  std::tuple<double>>() 
> <<::std::endl;
>     std::cout<< is_specialization_of<std::vector, std::tuple<double>>() 
> <<::std::endl;
>     std::cout<< is_specialization_of<std::array,  std::tuple<double>>() 
> <<::std::endl;
>     return 0;
> }
>
>
> Peter
>
>
>

-- 

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<div dir=3D"ltr">How it would help? `template &lt;class...&gt; class Templa=
te` still cant accept `<code><span style=3D"color:#000">std</span><span sty=
le=3D"color:#660">::</span><span style=3D"color:#000">arra<wbr>y</span><spa=
n style=3D"color:#660"></span></code>&lt;class,int&gt;`.<br><br>On Tuesday,=
 January 7, 2014 7:55:40 AM UTC+1, hun.nem...@gmail.com wrote:<blockquote c=
lass=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;border-left: 1px=
 #ccc solid;padding-left: 1ex;"><div dir=3D"ltr">I think compile time refle=
ction can handle this case.<br>Based on this paper (<a href=3D"https://gith=
ub.com/hun-nemethpeter/cpp-reflector-mini/blob/master/Proposal.md" target=
=3D"_blank" onmousedown=3D"this.href=3D'https://www.google.com/url?q\75http=
s%3A%2F%2Fgithub.com%2Fhun-nemethpeter%2Fcpp-reflector-mini%2Fblob%2Fmaster=
%2FProposal.md\46sa\75D\46sntz\0751\46usg\75AFQjCNFS9ji6XtoUPTCic92mCjgbLYX=
nnQ';return true;" onclick=3D"this.href=3D'https://www.google.com/url?q\75h=
ttps%3A%2F%2Fgithub.com%2Fhun-nemethpeter%2Fcpp-reflector-mini%2Fblob%2Fmas=
ter%2FProposal.md\46sa\75D\46sntz\0751\46usg\75AFQjCNFS9ji6XtoUPTCic92mCjgb=
LYXnnQ';return true;">https://github.com/hun-<wbr>nemethpeter/cpp-reflector=
-<wbr>mini/blob/master/Proposal.md</a>),<br>the result will be similar to t=
his:<br><br><br><div style=3D"background-color:rgb(250,250,250);border-colo=
r:rgb(187,187,187);border-style:solid;border-width:1px;word-wrap:break-word=
"><code><div><span style=3D"color:#800">// driver</span><span style=3D"colo=
r:#000"><br></span><span style=3D"color:#008">struct</span><span style=3D"c=
olor:#000"> </span><span style=3D"color:#606">SpecializationDriver</span><s=
pan style=3D"color:#000"><br></span><span style=3D"color:#660">{</span><spa=
n style=3D"color:#000"><br>&nbsp; &nbsp; </span><span style=3D"color:#008">=
constexpr</span><span style=3D"color:#000"> </span><span style=3D"color:#60=
6">SpecializationDriver</span><span style=3D"color:#660">(</span><span styl=
e=3D"color:#008">const</span><span style=3D"color:#000"> meta</span><span s=
tyle=3D"color:#660">::</span><span style=3D"color:#000">template_template_d=
ecl</span><span style=3D"color:#660">&amp;</span><span style=3D"color:#000"=
> templateTemplateDecl</span><span style=3D"color:#660">,</span><span style=
=3D"color:#000"> <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp=
; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;</sp=
an><span style=3D"color:#008">const</span><span style=3D"color:#000"> meta<=
/span><span style=3D"color:#660">::</span><span style=3D"color:#000">templa=
te_decl</span><span style=3D"color:#660">&amp;</span><span style=3D"color:#=
000"> templateDecl</span><span style=3D"color:#660">)</span><span style=3D"=
color:#000"><br>&nbsp; &nbsp; &nbsp; </span><span style=3D"color:#660">:</s=
pan><span style=3D"color:#000"> result</span><span style=3D"color:#660">(</=
span><span style=3D"color:#000">templateTemplateDecl</span><span style=3D"c=
olor:#660">.</span><span style=3D"color:#000">ge<wbr>tName</span><span styl=
e=3D"color:#660">()</span><span style=3D"color:#000"> </span><span style=3D=
"color:#660">=3D=3D</span><span style=3D"color:#000"> templateDecl</span><s=
pan style=3D"color:#660">.</span><span style=3D"color:#000">getName</span><=
span style=3D"color:#660">())</span><span style=3D"color:#000"> </span><spa=
n style=3D"color:#660">{</span><span style=3D"color:#000"> </span><span sty=
le=3D"color:#660">}</span><span style=3D"color:#000"><br>&nbsp; &nbsp; </sp=
an><span style=3D"color:#008">constexpr</span><span style=3D"color:#000"> <=
/span><span style=3D"color:#008">bool</span><span style=3D"color:#000"> res=
ult</span><span style=3D"color:#660">;</span><span style=3D"color:#000"><br=
></span><span style=3D"color:#660">};</span><span style=3D"color:#000"><br>=
<br></span><span style=3D"color:#008">template</span><span style=3D"color:#=
660">&lt;</span><span style=3D"color:#008">template</span><span style=3D"co=
lor:#000"> </span><span style=3D"color:#660">&lt;</span><span style=3D"colo=
r:#008">class</span><span style=3D"color:#660">...&gt;</span><span style=3D=
"color:#000"> </span><span style=3D"color:#008">class</span><span style=3D"=
color:#000"> </span><span style=3D"color:#606">Template</span><span style=
=3D"color:#660">,</span><span style=3D"color:#000"> </span><span style=3D"c=
olor:#008">class</span><span style=3D"color:#000"> T</span><span style=3D"c=
olor:#660">&gt;</span><span style=3D"color:#000"> $use</span><span style=3D=
"color:#660">(</span><span style=3D"color:#606">SpecializationDriver</span>=
<span style=3D"color:#000"> driver</span><span style=3D"color:#660">)</span=
><span style=3D"color:#000"><br></span><span style=3D"color:#008">bool</spa=
n><span style=3D"color:#000"> is_specialization_of</span><span style=3D"col=
or:#660">()</span><span style=3D"color:#000"><br></span><span style=3D"colo=
r:#660">{</span><span style=3D"color:#000"><br>&nbsp; &nbsp;</span><span st=
yle=3D"color:#008">return</span><span style=3D"color:#000"> driver</span><s=
pan style=3D"color:#660">.</span><span style=3D"color:#000">result</span><s=
pan style=3D"color:#660">;</span><span style=3D"color:#000"><br></span><spa=
n style=3D"color:#660">}</span><span style=3D"color:#000"><br></span><span =
style=3D"color:#000"><br></span><span style=3D"color:#008">int</span><span =
style=3D"color:#000"> main</span><span style=3D"color:#660">()</span><span =
style=3D"color:#000"><br></span><span style=3D"color:#660">{</span><span st=
yle=3D"color:#000"><br>&nbsp; &nbsp; std</span><span style=3D"color:#660">:=
:</span><span style=3D"color:#000">cout</span><span style=3D"color:#660">&l=
t;&lt;</span><span style=3D"color:#000"> is_specialization_of</span><span s=
tyle=3D"color:#660">&lt;</span><span style=3D"color:#000">std</span><span s=
tyle=3D"color:#660">::</span><span style=3D"color:#000">tupl<wbr>e</span><s=
pan style=3D"color:#660">,</span><span style=3D"color:#000"> &nbsp;std</spa=
n><span style=3D"color:#660">::</span><span style=3D"color:#000">tuple</spa=
n><span style=3D"color:#080">&lt;double&gt;</span><span style=3D"color:#660=
">&gt;()</span><span style=3D"color:#000"> </span><span style=3D"color:#660=
">&lt;&lt;::</span><span style=3D"color:#000">std</span><span style=3D"colo=
r:#660">::</span><span style=3D"color:#000">endl</span><span style=3D"color=
:#660">;</span><span style=3D"color:#000"><br>&nbsp; &nbsp; std</span><span=
 style=3D"color:#660">::</span><span style=3D"color:#000">cout</span><span =
style=3D"color:#660">&lt;&lt;</span><span style=3D"color:#000"> is_speciali=
zation_of</span><span style=3D"color:#660">&lt;</span><span style=3D"color:=
#000">std</span><span style=3D"color:#660">::</span><span style=3D"color:#0=
00">vect<wbr>or</span><span style=3D"color:#660">,</span><span style=3D"col=
or:#000"> std</span><span style=3D"color:#660">::</span><span style=3D"colo=
r:#000">tuple</span><span style=3D"color:#080">&lt;double&gt;</span><span s=
tyle=3D"color:#660">&gt;()</span><span style=3D"color:#000"> </span><span s=
tyle=3D"color:#660">&lt;&lt;::</span><span style=3D"color:#000">std</span><=
span style=3D"color:#660">::</span><span style=3D"color:#000">endl</span><s=
pan style=3D"color:#660">;</span><span style=3D"color:#000"><br>&nbsp; &nbs=
p; std</span><span style=3D"color:#660">::</span><span style=3D"color:#000"=
>cout</span><span style=3D"color:#660">&lt;&lt;</span><span style=3D"color:=
#000"> is_specialization_of</span><span style=3D"color:#660">&lt;</span><sp=
an style=3D"color:#000">std</span><span style=3D"color:#660">::</span><span=
 style=3D"color:#000">arra<wbr>y</span><span style=3D"color:#660">,</span><=
span style=3D"color:#000"> &nbsp;std</span><span style=3D"color:#660">::</s=
pan><span style=3D"color:#000">tuple</span><span style=3D"color:#080">&lt;d=
ouble&gt;</span><span style=3D"color:#660">&gt;()</span><span style=3D"colo=
r:#000"> </span><span style=3D"color:#660">&lt;&lt;::</span><span style=3D"=
color:#000">std</span><span style=3D"color:#660">::</span><span style=3D"co=
lor:#000">endl</span><span style=3D"color:#660">;</span><span style=3D"colo=
r:#000"><br>&nbsp; &nbsp; </span><span style=3D"color:#008">return</span><s=
pan style=3D"color:#000"> </span><span style=3D"color:#066">0</span><span s=
tyle=3D"color:#660">;</span><span style=3D"color:#000"><br></span><span sty=
le=3D"color:#660">}</span></div></code></div><br><br>Peter<br><br><div dir=
=3D"ltr"><br></div></div></blockquote></div>

<p></p>

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