public void ListExtend()
{
var src = list(1, 2, 3, 4, 5);
var f = func((Lst <int> x) => Lst.foldl(operators.add, 0, x));
var result = Lst.Extend <int, int>().extend(f)(src);
var expect = list(15, 14, 12, 9, 5);
claim.equal(expect, result);
}