multi_index

[Ellery Newcomer]

On 03/05/2012 07:05 AM, Andrei Alexandrescu wrote:
>
> Great! I meant for a long time to suggest Steve Schveighoffer to accept
> a variadic number of predicates for the red-black tree. This is even
> more general (nevertheless I still think it would be great if
> RedBlackTree accepted multiple predicates).
>
> Andrei
>
>

The point of that would just be to have your collection sorted multiple 
ways, right? It kinda seems like multi_index is most useful in that 
case, but then I don't use multi_index that often, so I don't know.

It would be a nice addition for RedBlackTree.


<code golf>

import multi_index;
import replace;

template RBTreeZ(Value, Preds...){
     template Splat(size_t i, size_t N){
         static if(i >= N) enum Splat = "";
         else{
             enum Splat = Replace!(q{
                 OrderedUnique!("a", Preds[$i]),
             }, "$i",i) ~ Splat!(i+1, N);
         }
     }
     enum ss = (Replace!( q{
         alias MultiIndexContainer!(Value,
             IndexedBy!($indeces)) RBTreeZ;
     }, "$indeces",Splat!(0,Preds.length)));
     mixin(ss);
}
void main(){
     alias RBTreeZ!(int, "a<b", "a>b") MahRBTree;
     // it compiles; good enough for me
}

</code golf>