UF ML

fun create [] = []
	| create (x::y) = (x,x)::(create y);

exception nopepuntoexe;

fun findAux x [] z = raise nopepuntoexe
	| findAux x ((a,b)::c) z =
		if x = a andalso a = b
			then
				b
			else
				if x = a
					then
						findAux b z z
					else
						findAux x c z

fun find x a = findAux x a a;

fun unionAux x y [] rest k = raise nopepuntoexe
	| unionAux x y ((a,b)::c) rest k = if k = a
											then
												rest@((a,x)::c)
											else
												unionAux x y c (rest@[(a,b)]) k;

fun union x y a = unionAux x y a [] (find y a);


val l = create([1,2,3,4,5,6]);