rascal>import List;
ok

rascal>a = [1, 4, 2, 3, 5];
list[int]: [1,4,2,3,5]

rascal>sort(a)
list[int]: [1,2,3,4,5]

rascal>sort(a, bool(int a, int b){return a >= b;})
list[int]: [5,4,3,2,1]