Re: [boost] [multi_index] Taking advantage of C++17 auto template params to simplify key specification

Subject: Re: [boost] [multi_index] Taking advantage of C++17 auto template params to simplify key specification
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2017-09-27 11:23:14

On 09/27/17 13:53, Joaquin M López Muñoz via Boost wrote:
> Consider the following:
> 
>  Â  struct element
>  Â  {
>  Â  Â  int x;
>  Â Â Â  int f()const{return x;}
>  Â  };
> 
>  Â  int gf(const element& e){return e.x;}
> 
>  Â  using container=multi_index_container<
>  Â Â Â  element,
>  Â Â Â  indexed_by<
> ordered_unique<member<element,int,&element::x>>,
> ordered_unique<const_mem_fun<element,int,&element::f>>,
>  Â Â Â Â Â  ordered_unique<global_fun<const element&,int,&gf>>
>  Â Â Â  >
>  Â  >;
> 
> With the advent in C++17 of auto non-type template parameters, it is 
> very easy to
> provide a boost::multi_index::key class template so that we can write:
> 
>  Â  using container=multi_index_container<
>  Â Â Â  element,
>  Â Â Â  indexed_by<
>  Â Â Â Â Â  ordered_unique<key<&element::x>>,
>  Â Â Â Â Â  ordered_unique<key<&element::f>>,
>  Â Â Â Â Â  ordered_unique<key<&gf>>
>  Â Â Â  >
>  Â  >;
> 
> (Example at http://coliru.stacked-crooked.com/a/5742c768cc093c03 ).
> 
> Is there interest in adding this to Boost.MultiIndex? Comments on this or
> alternative syntaxes?

Looks interesting. The C++03 version always seemed verbose to me. Will 
it also support function objects for key extraction?