Check if an element is within a sequence

Question

how to check if an element is contained within a sequence? I expected some Seq.contains, but i could not find it. Thanks

EDIT: Or, for an easier task, how to make the diff between two sequences? Like, getting all the elements within a list that doesn not belong to another (or that do)?

Answer 1

Little bit simpler:

let contains x = Seq.exists ((=) x)

Answer 2

Seq.exists

let testseq = seq [ 1; 2; 3; 4 ]
let equalsTwo n = (n = 2)
let containsTwo = Seq.exists equalsTwo testseq