reindex.d

auto reindex(string indexstring,string lengthstring="l",R)(R range){
	static struct reindex_{
		R range;
		int j=0;
		auto opIndex(int i){
			i+=j;
			import basic;
			mixin("return range["~indexstring~"];");
		}
		auto length(){
			auto l=range.length;
			return mixin(lengthstring)-j;
		}
		auto front(){
			return this[0];
		}
		void popFront(){
			j++;
		}
		bool empty(){
			return length==0;
		}
	}
	return reindex_(range);
}
unittest{
	import basic;
	auto foo=iota(0,5);
	auto bar=iota(0,10);

	foo.reindex!("$-i-1").writeln;
	bar.reindex!("$-i-1").writeln;
	
	foo.reindex!("min($-1,max(0,i-1))","l+2").writeln;
	bar.reindex!("min($-1,max(0,i-1))","l+2").writeln;
	
	foo.reindex!("min(i,($-1)*2-i+1)","l*2").writeln;
	bar.reindex!("min(i,($-1)*2-i+1)","l*2").writeln;
}