Distinguish recursive Templates

[Timon Gehr via Digitalmars-d-learn]

On 05/23/2015 12:12 AM, Manfred Nowak wrote:
> Matt Kline wrote:
>
>> isn't making any use of the template argument T
>
> Correct. I do not know how to use `T' to determine the recursion depth of
> the template---and I want no further parameter.
>
> -manfred
>

import std.stdio, std.range, std.algorithm;

template getDepth(T){
     static if(is(T==Set!S,S)) enum getDepth=1+getDepth!S;
     else enum getDepth=0;
}
class Set(T){
     override string toString(){
         enum r="Set".repeat.take(getDepth!Set).join;
         return r;
     }
}
void main(){
     auto s0=new Set!uint;
     writeln(s0); // writes Set
     auto s1=new Set!(Set!uint);
     writeln(s1); // writes SetSet
}