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Hi,

As of now it is not possible to alternate template parameters of different
value categorie (auto, int, class, template<> class, etc...) in a parameter
pack.
To circumvent this limitation the solution is to rely on the "tag" pattern.
Here's a basic example of this technique.

//library code (used for instance by boost's Mpl)
template<class, int> struct tag {};

//often accompanied by other tools

//will require documentation indicating that only a "tag" structure is a
valid parameter
template<class... Args> struct actual_usefull_type {};

//user code
int main()
{
   actual_usefull_type<tag<int, 42>, /*etc.*/> x;
}

My issues with the above are this fold:
- Requires the user to use internal/detail tools to use the type.
- The requirement to use the "tag" structure might not be self evident
without good documentation.
- Is often long and ugly in real-life example

My way to solve this would look as follow:

template<{class T, int I}... Args> //each element of Args is an anonymous
type containing a using named 'T' and a static constexpr global named 'I'
struct actual_usefull_type
{
     //access the parameter through Args. For instance Args::T
};

int main()
{
    actual_useful_type<{int, 42}, ...> x; // {int, 42} parsed as a template
argument list. converted into an anonymous class
}

I believe the above would be much cleaner/simpler.
This would make a named tuple implementation expressible as follows:

template<{class Type, std::fixed_string /*C++20*/ Name = ""}... Args>
struct named_tuple : std::tuple<Args::Type...>
{
    using std::tuple<Args::Type...>::tuple;

    template<std::fixed_string Name>
    static constexpr size_t index()
    {
       size_t i = 0;
       (... || (Name == Args::Args || (++i, false)));
       return (i >= sizeof...(Args) ? static_cast<size_t>(-1) : i;
    }

    template<std::fixed_string Name, size_t I = index<Name>()>
    requires I != static_cast<size_t>(-1)
    constexpr decltype(auto) get() const { return std::get<I>(*this); }

    template<std::fixed_string Name, size_t I = index<Name>()>
    requires I != static_cast<size_t>(-1)
    constexpr decltype(auto) get() { return std::get<I>(*this); }
};

int main()
{
   named_tuple<{int, "age"}, {std::string, "name"}, some_type /*same as
{some_type}*/> user;
   user.get<"age">();
   user.get<"name">();
   std::get<2>(user);
}


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<div dir=3D"ltr">Hi,<div><br></div><div>As of now it is not possible to alt=
ernate template parameters of different value categorie (auto, int, class, =
template&lt;&gt; class, etc...) in a parameter pack.</div><div>To circumven=
t this limitation the solution is to rely on the &quot;tag&quot; pattern.</=
div><div>Here&#39;s a basic example of this technique.<br></div><div><br></=
div><div class=3D"prettyprint" style=3D"background-color: rgb(250, 250, 250=
); border-color: rgb(187, 187, 187); border-style: solid; border-width: 1px=
; word-wrap: break-word;"><code class=3D"prettyprint"><div class=3D"subpret=
typrint"><span style=3D"color: #800;" class=3D"styled-by-prettify">//librar=
y code (used for instance by boost&#39;s Mpl)</span><span style=3D"color: #=
000;" class=3D"styled-by-prettify"><br></span><span style=3D"color: #008;" =
class=3D"styled-by-prettify">template</span><span style=3D"color: #660;" cl=
ass=3D"styled-by-prettify">&lt;</span><span style=3D"color: #008;" class=3D=
"styled-by-prettify">class</span><span style=3D"color: #660;" class=3D"styl=
ed-by-prettify">,</span><span style=3D"color: #000;" class=3D"styled-by-pre=
ttify"> </span><span style=3D"color: #008;" class=3D"styled-by-prettify">in=
t</span><span style=3D"color: #660;" class=3D"styled-by-prettify">&gt;</spa=
n><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span s=
tyle=3D"color: #008;" class=3D"styled-by-prettify">struct</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"> tag </span><span style=3D"c=
olor: #660;" class=3D"styled-by-prettify">{};</span><span style=3D"color: #=
000;" class=3D"styled-by-prettify"><br><br></span><span style=3D"color: #80=
0;" class=3D"styled-by-prettify">//often accompanied by other tools</span><=
span style=3D"color: #000;" class=3D"styled-by-prettify"><br><br></span><sp=
an style=3D"color: #800;" class=3D"styled-by-prettify">//will require docum=
entation indicating that only a &quot;tag&quot; structure is a valid parame=
ter</span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br></s=
pan><span style=3D"color: #008;" class=3D"styled-by-prettify">template</spa=
n><span style=3D"color: #660;" class=3D"styled-by-prettify">&lt;</span><spa=
n style=3D"color: #008;" class=3D"styled-by-prettify">class</span><span sty=
le=3D"color: #660;" class=3D"styled-by-prettify">...</span><span style=3D"c=
olor: #000;" class=3D"styled-by-prettify"> </span><span style=3D"color: #60=
6;" class=3D"styled-by-prettify">Args</span><span style=3D"color: #660;" cl=
ass=3D"styled-by-prettify">&gt;</span><span style=3D"color: #000;" class=3D=
"styled-by-prettify"> </span><span style=3D"color: #008;" class=3D"styled-b=
y-prettify">struct</span><span style=3D"color: #000;" class=3D"styled-by-pr=
ettify"> actual_usefull_type </span><span style=3D"color: #660;" class=3D"s=
tyled-by-prettify">{};</span><span style=3D"color: #000;" class=3D"styled-b=
y-prettify"><br><br></span><span style=3D"color: #800;" class=3D"styled-by-=
prettify">//user code</span><span style=3D"color: #000;" class=3D"styled-by=
-prettify"><br></span><span style=3D"color: #008;" class=3D"styled-by-prett=
ify">int</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> m=
ain</span><span style=3D"color: #660;" class=3D"styled-by-prettify">()</spa=
n><span style=3D"color: #000;" class=3D"styled-by-prettify"><br></span><spa=
n style=3D"color: #660;" class=3D"styled-by-prettify">{</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"><br>=C2=A0 =C2=A0actual_usef=
ull_type</span><span style=3D"color: #660;" class=3D"styled-by-prettify">&l=
t;</span><span style=3D"color: #000;" class=3D"styled-by-prettify">tag</spa=
n><span style=3D"color: #660;" class=3D"styled-by-prettify">&lt;</span><spa=
n style=3D"color: #008;" class=3D"styled-by-prettify">int</span><span style=
=3D"color: #660;" class=3D"styled-by-prettify">,</span><span style=3D"color=
: #000;" class=3D"styled-by-prettify"> </span><span style=3D"color: #066;" =
class=3D"styled-by-prettify">42</span><span style=3D"color: #660;" class=3D=
"styled-by-prettify">&gt;,</span><span style=3D"color: #000;" class=3D"styl=
ed-by-prettify"> </span><span style=3D"color: #800;" class=3D"styled-by-pre=
ttify">/*etc.*/</span><span style=3D"color: #660;" class=3D"styled-by-prett=
ify">&gt;</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> =
x</span><span style=3D"color: #660;" class=3D"styled-by-prettify">;</span><=
span style=3D"color: #000;" class=3D"styled-by-prettify"><br></span><span s=
tyle=3D"color: #660;" class=3D"styled-by-prettify">}</span></div></code></d=
iv><div><br></div><div>My issues with the above are this fold:</div><div>- =
Requires the user to use internal/detail tools to use the type.</div><div>-=
 The requirement to use the &quot;tag&quot; structure might not be self evi=
dent without good documentation.</div><div>- Is often long and ugly in real=
-life example</div><div><br></div><div>My way to solve this would look as f=
ollow:</div><div><br></div><div class=3D"prettyprint" style=3D"background-c=
olor: rgb(250, 250, 250); border-color: rgb(187, 187, 187); border-style: s=
olid; border-width: 1px; word-wrap: break-word;"><code class=3D"prettyprint=
"><div class=3D"subprettyprint"><span style=3D"color: #008;" class=3D"style=
d-by-prettify">template</span><span style=3D"color: #660;" class=3D"styled-=
by-prettify">&lt;{</span><span style=3D"color: #008;" class=3D"styled-by-pr=
ettify">class</span><span style=3D"color: #000;" class=3D"styled-by-prettif=
y"> T</span><span style=3D"color: #660;" class=3D"styled-by-prettify">,</sp=
an><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span =
style=3D"color: #008;" class=3D"styled-by-prettify">int</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"> I</span><span style=3D"colo=
r: #660;" class=3D"styled-by-prettify">}...</span><span style=3D"color: #00=
0;" class=3D"styled-by-prettify"> </span><span style=3D"color: #606;" class=
=3D"styled-by-prettify">Args</span><span style=3D"color: #660;" class=3D"st=
yled-by-prettify">&gt;</span><span style=3D"color: #000;" class=3D"styled-b=
y-prettify"> </span><span style=3D"color: #800;" class=3D"styled-by-prettif=
y">//each element of Args is an anonymous type containing a using named &#3=
9;T&#39; and a static constexpr global named &#39;I&#39;</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"><br></span><span style=3D"co=
lor: #008;" class=3D"styled-by-prettify">struct</span><span style=3D"color:=
 #000;" class=3D"styled-by-prettify"> actual_usefull_type<br></span><span s=
tyle=3D"color: #660;" class=3D"styled-by-prettify">{</span><span style=3D"c=
olor: #000;" class=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 =C2=A0</span><s=
pan style=3D"color: #800;" class=3D"styled-by-prettify">//access the parame=
ter through Args. For instance Args::T</span><span style=3D"color: #000;" c=
lass=3D"styled-by-prettify"><br></span><span style=3D"color: #660;" class=
=3D"styled-by-prettify">};</span><span style=3D"color: #000;" class=3D"styl=
ed-by-prettify"><br><br></span><span style=3D"color: #008;" class=3D"styled=
-by-prettify">int</span><span style=3D"color: #000;" class=3D"styled-by-pre=
ttify"> main</span><span style=3D"color: #660;" class=3D"styled-by-prettify=
">()</span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br></=
span><span style=3D"color: #660;" class=3D"styled-by-prettify">{</span><spa=
n style=3D"color: #000;" class=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 act=
ual_useful_type</span><span style=3D"color: #660;" class=3D"styled-by-prett=
ify">&lt;{</span><span style=3D"color: #008;" class=3D"styled-by-prettify">=
int</span><span style=3D"color: #660;" class=3D"styled-by-prettify">,</span=
><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span st=
yle=3D"color: #066;" class=3D"styled-by-prettify">42</span><span style=3D"c=
olor: #660;" class=3D"styled-by-prettify">},</span><span style=3D"color: #0=
00;" class=3D"styled-by-prettify"> </span><span style=3D"color: #660;" clas=
s=3D"styled-by-prettify">...&gt;</span><span style=3D"color: #000;" class=
=3D"styled-by-prettify"> x</span><span style=3D"color: #660;" class=3D"styl=
ed-by-prettify">;</span><span style=3D"color: #000;" class=3D"styled-by-pre=
ttify"> </span><span style=3D"color: #800;" class=3D"styled-by-prettify">//=
 {int, 42} parsed as a template argument list. converted into an anonymous =
class</span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br><=
/span><span style=3D"color: #660;" class=3D"styled-by-prettify">}</span><sp=
an style=3D"color: #000;" class=3D"styled-by-prettify"><br></span></div></c=
ode></div><div><br></div>I believe the above would be much cleaner/simpler.=
<div>This would make a named tuple implementation expressible as follows:</=
div><div><br></div><div class=3D"prettyprint" style=3D"background-color: rg=
b(250, 250, 250); border-color: rgb(187, 187, 187); border-style: solid; bo=
rder-width: 1px; word-wrap: break-word;"><code class=3D"prettyprint"><div c=
lass=3D"subprettyprint"><span style=3D"color: #008;" class=3D"styled-by-pre=
ttify">template</span><span style=3D"color: #660;" class=3D"styled-by-prett=
ify">&lt;{</span><span style=3D"color: #008;" class=3D"styled-by-prettify">=
class</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </sp=
an><span style=3D"color: #606;" class=3D"styled-by-prettify">Type</span><sp=
an style=3D"color: #660;" class=3D"styled-by-prettify">,</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"> std</span><span style=3D"co=
lor: #660;" class=3D"styled-by-prettify">::</span><span style=3D"color: #00=
0;" class=3D"styled-by-prettify">fixed_string </span><span style=3D"color: =
#800;" class=3D"styled-by-prettify">/*C++20*/</span><span style=3D"color: #=
000;" class=3D"styled-by-prettify"> </span><span style=3D"color: #606;" cla=
ss=3D"styled-by-prettify">Name</span><span style=3D"color: #000;" class=3D"=
styled-by-prettify"> </span><span style=3D"color: #660;" class=3D"styled-by=
-prettify">=3D</span><span style=3D"color: #000;" class=3D"styled-by-pretti=
fy"> </span><span style=3D"color: #080;" class=3D"styled-by-prettify">&quot=
;&quot;</span><span style=3D"color: #660;" class=3D"styled-by-prettify">}..=
..</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><=
span style=3D"color: #606;" class=3D"styled-by-prettify">Args</span><span s=
tyle=3D"color: #660;" class=3D"styled-by-prettify">&gt;</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"><br></span><span style=3D"co=
lor: #008;" class=3D"styled-by-prettify">struct</span><span style=3D"color:=
 #000;" class=3D"styled-by-prettify"> named_tuple </span><span style=3D"col=
or: #660;" class=3D"styled-by-prettify">:</span><span style=3D"color: #000;=
" class=3D"styled-by-prettify"> std</span><span style=3D"color: #660;" clas=
s=3D"styled-by-prettify">::</span><span style=3D"color: #000;" class=3D"sty=
led-by-prettify">tuple</span><span style=3D"color: #660;" class=3D"styled-b=
y-prettify">&lt;</span><span style=3D"color: #606;" class=3D"styled-by-pret=
tify">Args</span><span style=3D"color: #660;" class=3D"styled-by-prettify">=
::</span><span style=3D"color: #606;" class=3D"styled-by-prettify">Type</sp=
an><span style=3D"color: #660;" class=3D"styled-by-prettify">...&gt;</span>=
<span style=3D"color: #000;" class=3D"styled-by-prettify"><br></span><span =
style=3D"color: #660;" class=3D"styled-by-prettify">{</span><span style=3D"=
color: #000;" class=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 </span><span s=
tyle=3D"color: #008;" class=3D"styled-by-prettify">using</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"> std</span><span style=3D"co=
lor: #660;" class=3D"styled-by-prettify">::</span><span style=3D"color: #00=
0;" class=3D"styled-by-prettify">tuple</span><span style=3D"color: #660;" c=
lass=3D"styled-by-prettify">&lt;</span><span style=3D"color: #606;" class=
=3D"styled-by-prettify">Args</span><span style=3D"color: #660;" class=3D"st=
yled-by-prettify">::</span><span style=3D"color: #606;" class=3D"styled-by-=
prettify">Type</span><span style=3D"color: #660;" class=3D"styled-by-pretti=
fy">...&gt;::</span><span style=3D"color: #000;" class=3D"styled-by-prettif=
y">tuple</span><span style=3D"color: #660;" class=3D"styled-by-prettify">;<=
/span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br><br>=C2=
=A0 =C2=A0 </span><span style=3D"color: #008;" class=3D"styled-by-prettify"=
>template</span><span style=3D"color: #660;" class=3D"styled-by-prettify">&=
lt;</span><span style=3D"color: #000;" class=3D"styled-by-prettify">std</sp=
an><span style=3D"color: #660;" class=3D"styled-by-prettify">::</span><span=
 style=3D"color: #000;" class=3D"styled-by-prettify">fixed_string </span><s=
pan style=3D"color: #606;" class=3D"styled-by-prettify">Name</span><span st=
yle=3D"color: #660;" class=3D"styled-by-prettify">&gt;</span><span style=3D=
"color: #000;" class=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 </span><span =
style=3D"color: #008;" class=3D"styled-by-prettify">static</span><span styl=
e=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"colo=
r: #008;" class=3D"styled-by-prettify">constexpr</span><span style=3D"color=
: #000;" class=3D"styled-by-prettify"> size_t index</span><span style=3D"co=
lor: #660;" class=3D"styled-by-prettify">()</span><span style=3D"color: #00=
0;" class=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 </span><span style=3D"co=
lor: #660;" class=3D"styled-by-prettify">{</span><span style=3D"color: #000=
;" class=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 =C2=A0 =C2=A0size_t i </s=
pan><span style=3D"color: #660;" class=3D"styled-by-prettify">=3D</span><sp=
an style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=
=3D"color: #066;" class=3D"styled-by-prettify">0</span><span style=3D"color=
: #660;" class=3D"styled-by-prettify">;</span><span style=3D"color: #000;" =
class=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 =C2=A0 =C2=A0</span><span st=
yle=3D"color: #660;" class=3D"styled-by-prettify">(...</span><span style=3D=
"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"color: #=
660;" class=3D"styled-by-prettify">||</span><span style=3D"color: #000;" cl=
ass=3D"styled-by-prettify"> </span><span style=3D"color: #660;" class=3D"st=
yled-by-prettify">(</span><span style=3D"color: #606;" class=3D"styled-by-p=
rettify">Name</span><span style=3D"color: #000;" class=3D"styled-by-prettif=
y"> </span><span style=3D"color: #660;" class=3D"styled-by-prettify">=3D=3D=
</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><s=
pan style=3D"color: #606;" class=3D"styled-by-prettify">Args</span><span st=
yle=3D"color: #660;" class=3D"styled-by-prettify">::</span><span style=3D"c=
olor: #606;" class=3D"styled-by-prettify">Args</span><span style=3D"color: =
#000;" class=3D"styled-by-prettify"> </span><span style=3D"color: #660;" cl=
ass=3D"styled-by-prettify">||</span><span style=3D"color: #000;" class=3D"s=
tyled-by-prettify"> </span><font color=3D"#666600"><span style=3D"color: #6=
60;" class=3D"styled-by-prettify">(++</span><span style=3D"color: #000;" cl=
ass=3D"styled-by-prettify">i</span><span style=3D"color: #660;" class=3D"st=
yled-by-prettify">,</span><span style=3D"color: #000;" class=3D"styled-by-p=
rettify"> </span><span style=3D"color: #008;" class=3D"styled-by-prettify">=
false</span><span style=3D"color: #660;" class=3D"styled-by-prettify">)));<=
/span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br>=C2=A0 =
=C2=A0 =C2=A0 =C2=A0</span><span style=3D"color: #008;" class=3D"styled-by-=
prettify">return</span><span style=3D"color: #000;" class=3D"styled-by-pret=
tify"> </span><span style=3D"color: #660;" class=3D"styled-by-prettify">(</=
span><span style=3D"color: #000;" class=3D"styled-by-prettify">i </span><sp=
an style=3D"color: #660;" class=3D"styled-by-prettify">&gt;=3D</span><span =
style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"=
color: #008;" class=3D"styled-by-prettify">sizeof</span><span style=3D"colo=
r: #660;" class=3D"styled-by-prettify">...(</span><span style=3D"color: #60=
6;" class=3D"styled-by-prettify">Args</span><span style=3D"color: #660;" cl=
ass=3D"styled-by-prettify">)</span><span style=3D"color: #000;" class=3D"st=
yled-by-prettify"> </span><span style=3D"color: #660;" class=3D"styled-by-p=
rettify">?</span><span style=3D"color: #000;" class=3D"styled-by-prettify">=
 </span><span style=3D"color: #008;" class=3D"styled-by-prettify">static_ca=
st</span><span style=3D"color: #080;" class=3D"styled-by-prettify">&lt;size=
_t&gt;</span><span style=3D"color: #660;" class=3D"styled-by-prettify">(-</=
span><span style=3D"color: #066;" class=3D"styled-by-prettify">1</span><spa=
n style=3D"color: #660;" class=3D"styled-by-prettify">)</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"color=
: #660;" class=3D"styled-by-prettify">:</span><span style=3D"color: #000;" =
class=3D"styled-by-prettify"> i</span><span style=3D"color: #660;" class=3D=
"styled-by-prettify">;</span><span style=3D"color: #000;" class=3D"styled-b=
y-prettify"><br></span></font><span style=3D"color: #000;" class=3D"styled-=
by-prettify">=C2=A0 =C2=A0 </span><span style=3D"color: #660;" class=3D"sty=
led-by-prettify">}</span><span style=3D"color: #000;" class=3D"styled-by-pr=
ettify"><br><br>=C2=A0 =C2=A0 </span><span style=3D"color: #008;" class=3D"=
styled-by-prettify">template</span><span style=3D"color: #660;" class=3D"st=
yled-by-prettify">&lt;</span><span style=3D"color: #000;" class=3D"styled-b=
y-prettify">std</span><span style=3D"color: #660;" class=3D"styled-by-prett=
ify">::</span><font color=3D"#000000"><span style=3D"color: #000;" class=3D=
"styled-by-prettify">fixed_string </span><span style=3D"color: #606;" class=
=3D"styled-by-prettify">Name</span><span style=3D"color: #660;" class=3D"st=
yled-by-prettify">,</span><span style=3D"color: #000;" class=3D"styled-by-p=
rettify"> size_t I </span><span style=3D"color: #660;" class=3D"styled-by-p=
rettify">=3D</span><span style=3D"color: #000;" class=3D"styled-by-prettify=
"> index</span><span style=3D"color: #660;" class=3D"styled-by-prettify">&l=
t;</span><span style=3D"color: #606;" class=3D"styled-by-prettify">Name</sp=
an><span style=3D"color: #660;" class=3D"styled-by-prettify">&gt;()&gt;</sp=
an><span style=3D"color: #000;" class=3D"styled-by-prettify"><br>=C2=A0 =C2=
=A0 requires I </span><span style=3D"color: #660;" class=3D"styled-by-prett=
ify">!=3D</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> =
</span><span style=3D"color: #008;" class=3D"styled-by-prettify">static_cas=
t</span><span style=3D"color: #080;" class=3D"styled-by-prettify">&lt;size_=
t&gt;</span><span style=3D"color: #660;" class=3D"styled-by-prettify">(-</s=
pan><span style=3D"color: #066;" class=3D"styled-by-prettify">1</span><span=
 style=3D"color: #660;" class=3D"styled-by-prettify">)</span><span style=3D=
"color: #000;" class=3D"styled-by-prettify"><br></span></font><span style=
=3D"color: #000;" class=3D"styled-by-prettify">=C2=A0 =C2=A0 </span><span s=
tyle=3D"color: #008;" class=3D"styled-by-prettify">constexpr</span><span st=
yle=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"co=
lor: #008;" class=3D"styled-by-prettify">decltype</span><span style=3D"colo=
r: #660;" class=3D"styled-by-prettify">(</span><span style=3D"color: #008;"=
 class=3D"styled-by-prettify">auto</span><span style=3D"color: #660;" class=
=3D"styled-by-prettify">)</span><span style=3D"color: #000;" class=3D"style=
d-by-prettify"> </span><span style=3D"color: #008;" class=3D"styled-by-pret=
tify">get</span><span style=3D"color: #660;" class=3D"styled-by-prettify">(=
)</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><=
span style=3D"color: #008;" class=3D"styled-by-prettify">const</span><span =
style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"=
color: #660;" class=3D"styled-by-prettify">{</span><span style=3D"color: #0=
00;" class=3D"styled-by-prettify"> </span><span style=3D"color: #008;" clas=
s=3D"styled-by-prettify">return</span><span style=3D"color: #000;" class=3D=
"styled-by-prettify"> std</span><span style=3D"color: #660;" class=3D"style=
d-by-prettify">::</span><span style=3D"color: #008;" class=3D"styled-by-pre=
ttify">get</span><span style=3D"color: #660;" class=3D"styled-by-prettify">=
&lt;</span><span style=3D"color: #000;" class=3D"styled-by-prettify">I</spa=
n><span style=3D"color: #660;" class=3D"styled-by-prettify">&gt;(*</span><s=
pan style=3D"color: #008;" class=3D"styled-by-prettify">this</span><span st=
yle=3D"color: #660;" class=3D"styled-by-prettify">);</span><span style=3D"c=
olor: #000;" class=3D"styled-by-prettify"> </span><span style=3D"color: #66=
0;" class=3D"styled-by-prettify">}</span><span style=3D"color: #000;" class=
=3D"styled-by-prettify"><br><br>=C2=A0 =C2=A0 </span><span style=3D"color: =
#008;" class=3D"styled-by-prettify">template</span><span style=3D"color: #6=
60;" class=3D"styled-by-prettify">&lt;</span><span style=3D"color: #000;" c=
lass=3D"styled-by-prettify">std</span><span style=3D"color: #660;" class=3D=
"styled-by-prettify">::</span><font color=3D"#000000"><span style=3D"color:=
 #000;" class=3D"styled-by-prettify">fixed_string </span><span style=3D"col=
or: #606;" class=3D"styled-by-prettify">Name</span><span style=3D"color: #6=
60;" class=3D"styled-by-prettify">,</span><span style=3D"color: #000;" clas=
s=3D"styled-by-prettify"> size_t I </span><span style=3D"color: #660;" clas=
s=3D"styled-by-prettify">=3D</span><span style=3D"color: #000;" class=3D"st=
yled-by-prettify"> index</span><span style=3D"color: #660;" class=3D"styled=
-by-prettify">&lt;</span><span style=3D"color: #606;" class=3D"styled-by-pr=
ettify">Name</span><span style=3D"color: #660;" class=3D"styled-by-prettify=
">&gt;()&gt;</span><span style=3D"color: #000;" class=3D"styled-by-prettify=
"><br>=C2=A0 =C2=A0 requires I </span><span style=3D"color: #660;" class=3D=
"styled-by-prettify">!=3D</span><span style=3D"color: #000;" class=3D"style=
d-by-prettify"> </span><span style=3D"color: #008;" class=3D"styled-by-pret=
tify">static_cast</span><span style=3D"color: #080;" class=3D"styled-by-pre=
ttify">&lt;size_t&gt;</span><span style=3D"color: #660;" class=3D"styled-by=
-prettify">(-</span><span style=3D"color: #066;" class=3D"styled-by-prettif=
y">1</span><span style=3D"color: #660;" class=3D"styled-by-prettify">)</spa=
n><span style=3D"color: #000;" class=3D"styled-by-prettify"><br></span></fo=
nt><span style=3D"color: #000;" class=3D"styled-by-prettify">=C2=A0 =C2=A0 =
</span><span style=3D"color: #008;" class=3D"styled-by-prettify">constexpr<=
/span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><sp=
an style=3D"color: #008;" class=3D"styled-by-prettify">decltype</span><span=
 style=3D"color: #660;" class=3D"styled-by-prettify">(</span><span style=3D=
"color: #008;" class=3D"styled-by-prettify">auto</span><span style=3D"color=
: #660;" class=3D"styled-by-prettify">)</span><span style=3D"color: #000;" =
class=3D"styled-by-prettify"> </span><span style=3D"color: #008;" class=3D"=
styled-by-prettify">get</span><span style=3D"color: #660;" class=3D"styled-=
by-prettify">()</span><span style=3D"color: #000;" class=3D"styled-by-prett=
ify"> </span><span style=3D"color: #660;" class=3D"styled-by-prettify">{</s=
pan><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span=
 style=3D"color: #008;" class=3D"styled-by-prettify">return</span><span sty=
le=3D"color: #000;" class=3D"styled-by-prettify"> std</span><span style=3D"=
color: #660;" class=3D"styled-by-prettify">::</span><span style=3D"color: #=
008;" class=3D"styled-by-prettify">get</span><span style=3D"color: #660;" c=
lass=3D"styled-by-prettify">&lt;</span><span style=3D"color: #000;" class=
=3D"styled-by-prettify">I</span><span style=3D"color: #660;" class=3D"style=
d-by-prettify">&gt;(*</span><span style=3D"color: #008;" class=3D"styled-by=
-prettify">this</span><span style=3D"color: #660;" class=3D"styled-by-prett=
ify">);</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </=
span><span style=3D"color: #660;" class=3D"styled-by-prettify">}</span><spa=
n style=3D"color: #000;" class=3D"styled-by-prettify"><br></span><span styl=
e=3D"color: #660;" class=3D"styled-by-prettify">};</span><span style=3D"col=
or: #000;" class=3D"styled-by-prettify"><br><br></span><span style=3D"color=
: #008;" class=3D"styled-by-prettify">int</span><span style=3D"color: #000;=
" class=3D"styled-by-prettify"> main</span><span style=3D"color: #660;" cla=
ss=3D"styled-by-prettify">()</span><span style=3D"color: #000;" class=3D"st=
yled-by-prettify"><br></span><span style=3D"color: #660;" class=3D"styled-b=
y-prettify">{</span><span style=3D"color: #000;" class=3D"styled-by-prettif=
y"><br>=C2=A0 =C2=A0named_tuple</span><span style=3D"color: #660;" class=3D=
"styled-by-prettify">&lt;{</span><span style=3D"color: #008;" class=3D"styl=
ed-by-prettify">int</span><font color=3D"#000000"><span style=3D"color: #66=
0;" class=3D"styled-by-prettify">,</span><span style=3D"color: #000;" class=
=3D"styled-by-prettify"> </span><span style=3D"color: #080;" class=3D"style=
d-by-prettify">&quot;age&quot;</span><span style=3D"color: #660;" class=3D"=
styled-by-prettify">},</span><span style=3D"color: #000;" class=3D"styled-b=
y-prettify"> </span><span style=3D"color: #660;" class=3D"styled-by-prettif=
y">{</span><span style=3D"color: #000;" class=3D"styled-by-prettify">std</s=
pan><span style=3D"color: #660;" class=3D"styled-by-prettify">::</span><spa=
n style=3D"color: #008;" class=3D"styled-by-prettify">string</span><span st=
yle=3D"color: #660;" class=3D"styled-by-prettify">,</span><span style=3D"co=
lor: #000;" class=3D"styled-by-prettify"> </span><span style=3D"color: #080=
;" class=3D"styled-by-prettify">&quot;name&quot;</span><span style=3D"color=
: #660;" class=3D"styled-by-prettify">},</span><span style=3D"color: #000;"=
 class=3D"styled-by-prettify"> some_type </span><span style=3D"color: #800;=
" class=3D"styled-by-prettify">/*same as {some_type}*/</span><span style=3D=
"color: #660;" class=3D"styled-by-prettify">&gt;</span><span style=3D"color=
: #000;" class=3D"styled-by-prettify"> user</span><span style=3D"color: #66=
0;" class=3D"styled-by-prettify">;</span><span style=3D"color: #000;" class=
=3D"styled-by-prettify"><br></span></font><span style=3D"color: #000;" clas=
s=3D"styled-by-prettify">=C2=A0 =C2=A0user</span><span style=3D"color: #660=
;" class=3D"styled-by-prettify">.</span><span style=3D"color: #008;" class=
=3D"styled-by-prettify">get</span><span style=3D"color: #660;" class=3D"sty=
led-by-prettify">&lt;</span><span style=3D"color: #080;" class=3D"styled-by=
-prettify">&quot;age&quot;</span><span style=3D"color: #660;" class=3D"styl=
ed-by-prettify">&gt;();</span><span style=3D"color: #000;" class=3D"styled-=
by-prettify"><br>=C2=A0 =C2=A0user</span><span style=3D"color: #660;" class=
=3D"styled-by-prettify">.</span><span style=3D"color: #008;" class=3D"style=
d-by-prettify">get</span><span style=3D"color: #660;" class=3D"styled-by-pr=
ettify">&lt;</span><span style=3D"color: #080;" class=3D"styled-by-prettify=
">&quot;name&quot;</span><span style=3D"color: #660;" class=3D"styled-by-pr=
ettify">&gt;();</span><span style=3D"color: #000;" class=3D"styled-by-prett=
ify"><br>=C2=A0 =C2=A0std</span><span style=3D"color: #660;" class=3D"style=
d-by-prettify">::</span><span style=3D"color: #008;" class=3D"styled-by-pre=
ttify">get</span><span style=3D"color: #660;" class=3D"styled-by-prettify">=
&lt;</span><span style=3D"color: #066;" class=3D"styled-by-prettify">2</spa=
n><span style=3D"color: #660;" class=3D"styled-by-prettify">&gt;(</span><sp=
an style=3D"color: #000;" class=3D"styled-by-prettify">user</span><span sty=
le=3D"color: #660;" class=3D"styled-by-prettify">);</span><span style=3D"co=
lor: #000;" class=3D"styled-by-prettify"><br></span><span style=3D"color: #=
660;" class=3D"styled-by-prettify">}</span></div></code></div><div><div><br=
></div></div><div><br></div></div>

<p></p>

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