anonymous template predicates

[Idan Arye via Digitalmars-d-learn]

On Thursday, 30 April 2015 at 21:01:36 UTC, Vlad Levenfeld wrote:
> I was wondering if there's a mechanism to make anonymous 
> templates, e.g.
>
> given:
>   enum Policy {A, B}
>   alias List = TypeTuple!(...);
>
> instead of this:
>
>   enum has_policy_A (T) = T.policy == Policy.A;
>   alias Result = Filter!(has_policy_A, List);
>
> use something like this:
>
>   Filter!(T => T.policy == Policy.A, List);
>
> I've tried templates that generate eponymous predicates from 
> mixed-in strings but these have a number of caveats that limit 
> their usability.

The syntax is a bit ugly, but it can be done: 
http://dpaste.dzfl.pl/d17912ccdeb9