1\DOC quadruple_of_list 2 3\TYPE {quadruple_of_list : 'a list -> 'a * 'a * 'a * 'a} 4 5\SYNOPSIS 6Turns a four-element list into a quadruple. 7 8\DESCRIBE 9{quadruple_of_list [x1, x2, x3, x4]} returns {(x1, x2, x3, x4)}. 10 11\FAILURE 12Fails if applied to a list that is not of length 4. 13 14\SEEALSO 15Lib.singleton_of_list, Lib.pair_of_list, Lib.triple_of_list. 16 17\ENDDOC 18