# Return the list L after applying Knuth shuffle. GAP also has the function Shuffle, which does the same.
ShuffleAlt := function(a)
    local i, j, n, t;
    n := Length(a);
    for i in [n, n - 1 .. 2] do
        j := Random(1, i);
        t := a[i];
        a[i] := a[j];
        a[j] := t;
    od;
    return a;
end;

# Return a "Permutation" object (a permutation of 1 .. n).
# They are printed in GAP, in cycle decomposition form.
PermShuffle := n -> PermList(ShuffleAlt([1 .. n]));

ShuffleAlt([1 .. 10]);
# [ 4, 7, 1, 5, 8, 2, 6, 9, 10, 3 ]

PermShuffle(10);
# (1,9)(2,3,6,4,5,10,8,7)

# One may also call the built-in random generator on the symmetric group :
Random(SymmetricGroup(10));
(1,8,2,5,9,6)(3,4,10,7)
