fixedPoints w
A permutation $p$ is a derangement if it has no fixed points.
i1 : p = permutation {3,1,2,5,4} o1 = Permutation{3, 1, 2, 5, 4} o1 : Permutation
i2 : isDerangement p o2 = true
The object isDerangement is a method function.