const xnor = (a, b) => a === b ? 1 : 0;

export function compare(pa, pb) {
	if (pa.length !== pb.length) {
		throw new Error(`attempted to compare proteins with different lengths: ${pa.length} vs ${pb.length}`);
	}
	return (1/pa.length) * pa
		.map((_, i) => xnor(pa[i], pb[i]))
		.reduce((acc, val) => acc + val, 0)
}