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P0091 is voted into C++17, but for outsiders it's unclear what
decisions/changes has been made since:

** What's the syntax settled for explicit deduction guides?*

The proposed syntax in P0091R2 is:
    *template < template-parameter-list > class-name (
parameter-declaration-clause ) -> simple-template-id*

The author also listed some alternatives and left the decision to the
committee, what's the committee's decision?
Is it possible for a syntax that doesn't require us to repeat the
class-name twice, e.g:
    *template-parameter-list > simple-template-id auto(
parameter-declaration-clause )*

template<typename Iter>
vector<typename iterator_traits<Iter>::value_type> auto(Iter b, Iter e);

** Are non-template explicit deduction guides allowed?*

template<class T>
struct S
{
    S(T);
};

S(char const*) -> S<std::string>;

S s{"hello"}; // deduced to S<std::string>

** Does the deduction work for aggregates?*

template<class A, class B>
struct Agg
{
    A a;
    B b;
};

Agg agg{1, 2.0}; // ok? deduced to Agg<int, double>

If the above doesn't work, will explicit deduction guides help?

template<class A, class B>
Agg(A a, B b) -> Agg<A, B>;


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<div dir=3D"ltr"><div>P0091 is voted into C++17, but for outsiders it&#39;s=
 unclear what decisions/changes has been made since:</div><div><br></div><d=
iv><b>* What&#39;s the syntax settled for explicit deduction guides?</b></d=
iv><div><br></div><div>The proposed syntax in P0091R2 is:</div><div>=C2=A0 =
=C2=A0 <i>template &lt; template-parameter-list &gt; class-name ( parameter=
-declaration-clause ) -&gt; simple-template-id</i></div><div><i><br></i></d=
iv><div>The author also listed some alternatives and left the decision to t=
he committee, what&#39;s the committee&#39;s decision?</div><div>Is it poss=
ible for a syntax that doesn&#39;t require us to repeat the class-name twic=
e, e.g:</div><div>=C2=A0 =C2=A0=C2=A0<i>template-parameter-list &gt; simple=
-template-id auto( parameter-declaration-clause )</i></div><div><br></div><=
div class=3D"prettyprint" style=3D"border: 1px solid rgb(187, 187, 187); wo=
rd-wrap: break-word; background-color: rgb(250, 250, 250);"><code class=3D"=
prettyprint"><div class=3D"subprettyprint"><span style=3D"color: #008;" cla=
ss=3D"styled-by-prettify">template</span><span style=3D"color: #660;" class=
=3D"styled-by-prettify">&lt;</span><span style=3D"color: #008;" class=3D"st=
yled-by-prettify">typename</span><span style=3D"color: #000;" class=3D"styl=
ed-by-prettify"> </span><span style=3D"color: #606;" class=3D"styled-by-pre=
ttify">Iter</span><span style=3D"color: #660;" class=3D"styled-by-prettify"=
>&gt;</span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br>v=
ector</span><span style=3D"color: #660;" class=3D"styled-by-prettify">&lt;<=
/span><span style=3D"color: #008;" class=3D"styled-by-prettify">typename</s=
pan><span style=3D"color: #000;" class=3D"styled-by-prettify"> iterator_tra=
its</span><span style=3D"color: #660;" class=3D"styled-by-prettify">&lt;</s=
pan><span style=3D"color: #606;" class=3D"styled-by-prettify">Iter</span><s=
pan style=3D"color: #660;" class=3D"styled-by-prettify">&gt;::</span><span =
style=3D"color: #000;" class=3D"styled-by-prettify">value_type</span><span =
style=3D"color: #660;" class=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-by-prettify">auto</span><span style=3D"color: #660=
;" class=3D"styled-by-prettify">(</span><span style=3D"color: #606;" class=
=3D"styled-by-prettify">Iter</span><span style=3D"color: #000;" class=3D"st=
yled-by-prettify"> b</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">Iter</sp=
an><span style=3D"color: #000;" class=3D"styled-by-prettify"> e</span><span=
 style=3D"color: #660;" class=3D"styled-by-prettify">);</span></div></code>=
</div><div><br></div><div><b>* Are non-template explicit deduction guides a=
llowed?</b></div><div><br></div><div class=3D"prettyprint" style=3D"border:=
 1px solid rgb(187, 187, 187); word-wrap: break-word; background-color: rgb=
(250, 250, 250);"><code class=3D"prettyprint"><div class=3D"subprettyprint"=
><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 s=
tyle=3D"color: #008;" class=3D"styled-by-prettify">class</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"> T</span><span style=3D"colo=
r: #660;" class=3D"styled-by-prettify">&gt;</span><span style=3D"color: #00=
0;" class=3D"styled-by-prettify"><br></span><span style=3D"color: #008;" cl=
ass=3D"styled-by-prettify">struct</span><span style=3D"color: #000;" class=
=3D"styled-by-prettify"> S<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 S</span><span style=3D"color: #660;" class=3D"=
styled-by-prettify">(</span><span style=3D"color: #000;" class=3D"styled-by=
-prettify">T</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><sp=
an style=3D"color: #000;" class=3D"styled-by-prettify"><br><br>S</span><spa=
n style=3D"color: #660;" class=3D"styled-by-prettify">(</span><span style=
=3D"color: #008;" class=3D"styled-by-prettify">char</span><span style=3D"co=
lor: #000;" class=3D"styled-by-prettify"> </span><span style=3D"color: #008=
;" class=3D"styled-by-prettify">const</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><span style=3D"color: #660;" class=3D"styled-by-=
prettify">-&gt;</span><span style=3D"color: #000;" class=3D"styled-by-prett=
ify"> S</span><span style=3D"color: #660;" class=3D"styled-by-prettify">&lt=
;</span><span style=3D"color: #000;" class=3D"styled-by-prettify">std</span=
><span style=3D"color: #660;" class=3D"styled-by-prettify">::</span><span s=
tyle=3D"color: #008;" class=3D"styled-by-prettify">string</span><span style=
=3D"color: #660;" class=3D"styled-by-prettify">&gt;;</span><span style=3D"c=
olor: #000;" class=3D"styled-by-prettify"><br><br>S s</span><span style=3D"=
color: #660;" class=3D"styled-by-prettify">{</span><span style=3D"color: #0=
80;" class=3D"styled-by-prettify">&quot;hello&quot;</span><span style=3D"co=
lor: #660;" class=3D"styled-by-prettify">};</span><span style=3D"color: #00=
0;" class=3D"styled-by-prettify"> </span><span style=3D"color: #800;" class=
=3D"styled-by-prettify">// deduced to S&lt;std::string&gt;</span></div></co=
de></div><div><br></div><div><b>* Does the deduction work for aggregates?</=
b></div><div><br></div><div class=3D"prettyprint" style=3D"border: 1px soli=
d rgb(187, 187, 187); word-wrap: break-word; background-color: rgb(250, 250=
, 250);"><code class=3D"prettyprint"><div class=3D"subprettyprint"><span st=
yle=3D"color: #008;" class=3D"styled-by-prettify">template</span><span styl=
e=3D"color: #660;" class=3D"styled-by-prettify">&lt;</span><span style=3D"c=
olor: #008;" class=3D"styled-by-prettify">class</span><span style=3D"color:=
 #000;" class=3D"styled-by-prettify"> A</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">class</span><span style=3D"color: #000;" class=3D"styled-by-pret=
tify"> B</span><span style=3D"color: #660;" class=3D"styled-by-prettify">&g=
t;</span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br></sp=
an><span style=3D"color: #008;" class=3D"styled-by-prettify">struct</span><=
span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span styl=
e=3D"color: #606;" class=3D"styled-by-prettify">Agg</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><span style=3D"color: #000;" cla=
ss=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 A a</span><span style=3D"color:=
 #660;" class=3D"styled-by-prettify">;</span><span style=3D"color: #000;" c=
lass=3D"styled-by-prettify"><br>=C2=A0 =C2=A0 B b</span><span style=3D"colo=
r: #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><span style=3D"color: #000;" class=3D"styl=
ed-by-prettify"><br><br></span><span style=3D"color: #606;" class=3D"styled=
-by-prettify">Agg</span><span style=3D"color: #000;" class=3D"styled-by-pre=
ttify"> agg</span><span style=3D"color: #660;" class=3D"styled-by-prettify"=
>{</span><span style=3D"color: #066;" class=3D"styled-by-prettify">1</span>=
<span style=3D"color: #660;" class=3D"styled-by-prettify">,</span><span sty=
le=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"col=
or: #066;" class=3D"styled-by-prettify">2.0</span><span style=3D"color: #66=
0;" class=3D"styled-by-prettify">};</span><span style=3D"color: #000;" clas=
s=3D"styled-by-prettify"> </span><span style=3D"color: #800;" class=3D"styl=
ed-by-prettify">// ok? deduced to Agg&lt;int, double&gt;</span></div></code=
></div><div><br></div><div>If the above doesn&#39;t work, will explicit ded=
uction guides help?</div><div><br></div><div class=3D"prettyprint" style=3D=
"border: 1px solid rgb(187, 187, 187); word-wrap: break-word; background-co=
lor: rgb(250, 250, 250);"><code class=3D"prettyprint"><div class=3D"subpret=
typrint"><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: #008;" class=3D"styled-by-prettify">class</span><spa=
n style=3D"color: #000;" class=3D"styled-by-prettify"> A</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">class</span><span style=3D"color: #000;" class=
=3D"styled-by-prettify"> B</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></span><span style=3D"color: #606;" class=3D"styled-by-pretti=
fy">Agg</span><span style=3D"color: #660;" class=3D"styled-by-prettify">(</=
span><span style=3D"color: #000;" class=3D"styled-by-prettify">A a</span><s=
pan style=3D"color: #660;" class=3D"styled-by-prettify">,</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"> B b</span><span style=3D"co=
lor: #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">-&gt;</span><span style=3D"color: #000;" class=3D"s=
tyled-by-prettify"> </span><span style=3D"color: #606;" class=3D"styled-by-=
prettify">Agg</span><span style=3D"color: #660;" class=3D"styled-by-prettif=
y">&lt;</span><span style=3D"color: #000;" class=3D"styled-by-prettify">A</=
span><span style=3D"color: #660;" class=3D"styled-by-prettify">,</span><spa=
n style=3D"color: #000;" class=3D"styled-by-prettify"> B</span><span style=
=3D"color: #660;" class=3D"styled-by-prettify">&gt;;</span></div></code></d=
iv><div><br></div><div><br></div></div>

<p></p>

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