get from tuple by type

[weaselcat via Digitalmars-d-learn]

On Sunday, 15 March 2015 at 22:21:04 UTC, ketmar wrote:
> On Sun, 15 Mar 2015 21:59:16 +0000, Charles Cooper wrote:
>
>> C++14 has:
>> template<class T, class... Types> constexpr T& 
>> get(tuple<Types...>& t);
>> Which allows you to get a member of the tuple struct by type. 
>> Is there
>> an idiomatic / library way to do this in D? Preferably by 
>> indexing.
>
> why indexing? functional programming is fun!
>
>   import std.typecons : tuple;
>
>   template GetByType(Type, Tuple...) {
>     import std.typecons : isTuple;
>     static if (Tuple.length == 0)
>       static assert(false, Type.stringof~" not found");
>     else static if (Tuple.length == 1 && 
> isTuple!(typeof(Tuple[0])))
>       enum GetByType = GetByType!(Type, Tuple[0].expand);
>     else static if (is(typeof(Tuple[0]) == Type))
>       enum GetByType = Tuple[0];
>     else
>       enum GetByType = GetByType!(Type, Tuple[1..$]);
>   }
>
>   static assert(2.5 == GetByType!(double, 1, 2.5));
>   static assert(2.5 == GetByType!(double, 1, 2.5, 3.1));
>   //static assert(2.5 == GetByType!(char, 1, 2.5, 3.1));
>   static assert(2.5 == GetByType!(double, std.typecons.tuple(1, 
> 2.5)));
>   static assert(2.5 == GetByType!(double, 
> std.typecons.tuple(1,2.5,3.1)));

Seems like a useful feature(useful enough to get past the C++ 
standards committee,) consider submitting a phobos PR?