how to get top N distinct elements from range?

[Andrea Fontana]

On Saturday, 9 March 2013 at 01:36:53 UTC, bearophile wrote:
>
> Is it a good idea to replace std.algorithm.filter with 
> something like that filter2 (plus some missing methods)?
>
> Bye,
> bearophile

Maybe two versions (filter and cachedFilter) or a bool template 
param?

I was thinking about @pure front() too: but I think it's a wrong 
assumption. The right assumption would be that front should 
return the same value until popFront is called again. It can read 
front value lazily from front() call. It can do a lot of impure 
things (lol) but it shouldn't change front "randomly" at each 
call.

I would improve distinct to support an alias pred = "a < b" to 
build a bst instead of an AA.

Or just a field like distinct!"a.id" (that should work with aa 
backend)