yes... I know they're circular... but is there ever more than one pair of whole integers described? I mean, could any two integers produce the same result as any other two integers, so that
[ f(x1,y1) , f(y1,x1) ] == [ f(x2,y2) , f(y2,x2) ] ?
If not... then this would satisfy to give a unique identifier of two ID's combined...