Sequence.swift

var g = (0..<10).generate()
let seq = lazy(AnySequence(anyGenerator { _ -> Int? in
        print("called") //prints "called" 11 times
        return g.next()
    }))
    .filter { $0 != 2 }
    .filter { $0 != 4 }

for x in seq {
    print("item: \(x)")
}