slideeach.d

import std;
auto takeUntil(R)(R base,R other){
    static struct Result{
        R base;
        R other;
        alias base this;
        bool empty()=>base==other;
    }
    return Result(base,other);
}
unittest{
	iota(5).takeUntil(iota(5).drop(3)).writeln;
}

template slideeach(alias cat,F...){
    void slideeach(R)(R r){
        struct sliceeach_{
            R active;
            R store;
            auto front(){
                int catagory=cat(store.front);
                //assert(catagory<F.length);assert(catagory>=0);
                while( ! active.empty && cat(active.front)==catagory){
                    active.popFront;
                }
                lable: switch(catagory){
                    static foreach(i;0..F.length){
                        case i:F[i](store.takeUntil(active)); break lable;
                    }
                    default: assert(0);
                }
				//F[catagory](store.takeUntil(active));
            }
            void popFront(){
                store=active;
            }
            bool empty()=>store.empty;
        }
        auto temp=sliceeach_(r,r);
        while( ! temp.empty){
            temp.front();
            temp.popFront;
        }
}}
unittest{
    int fizzbuzz(int i){
		if(i%15==0)return 0;
        if(i%5==0)return 1;
        if(i%3==0)return 2;
		return 3;
    }
    template print(string s){
		void print(R)(R r)=>writeln(s,":",r);
    }
    [15,30,45,3,6,5,10,9,1,2,4,6].slideeach!(
		fizzbuzz,
			print!"fizzbuzz",
			print!"buzz",
        	print!"fizz",
    		writeln);
}