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?