[std.algorithm.setops] cartesianReduction

[crazymonkyyy]

I suggest the inclusion of this code:

auto cartesianReduction(alias F,alias Vinit,alias Hinit,R1,R2,E)(R1 r1,R2 r2,E seed){
	auto r=cartesianProduct(r1,r2);
	alias R=typeof(r);
	E[] storage; storage.reserve(r2.length);
	foreach(e;r2.map!Vinit){
		storage~=e;
	}
	struct range{
		R r;
		E diagonal;
		E[] storage;
		int i;
		auto front()=>F(r.front[0],r.front[1],diagonal,storage[i],i==0?Hinit(r.front[0]):storage[i-1]);
		void popFront(){
			if(i>0){
				diagonal=storage[i];
			}
			storage[i]=front;
			i++;
			if(i==storage.length){
				diagonal=Hinit(r.front);
				i=0;
			}
			r.popFront;
		}
		bool empty()=>r.empty;
	}
	return range(r,seed,storage);
}

ai conversation: https://gemini.google.com/share/614e0ef1a71b with phoboes-ifyed code block

the ai is being very stupid deleting the seed parameter, and it expanding 30 lines into 200 lines but that looks like phobos style to me.

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Gentrification of the 3 "smith-waterman" algorithms, following the preexisting cartisianProduct naming