Why does filters in Swift iterate the collection twice?

Vote count:

1

The following code in Swift's playground or Console App:

let letters = ["A", "B", "C"]

letters.filter({
    (x : String) -> Bool in
    println(x)
    return true
})

Prints out:

A
B
C
A
B
C

Why does it iterate over the collection twice?

asked 48 secs ago

mythz

52.4k