The rsort function uses <= to compare elements of the list, which in turn calls upon ?.
i1 : rsort {g,d,w,s,c,a,r} o1 = {a, c, d, g, r, s, w} o1 : List
i2 : rsort {4,2,3,1} o2 = {4, 3, 2, 1} o2 : List
See also sort, <=, and ?.
