Why `double` is called 5 times and `filter` is called 4 times? Shouldn't they be called same amount of times? Shouldn't they both be called only twice as I have 2-element array?

expected_output

double 2
filter 4
double 8
filter 16
result: [4]

main.swift

func double(value: Int) -> Int {
  print("double \(value)")
  return value * 2
}

func filter(value: Int) -> Bool {
  print("filter \(value)")
  return value < 10
}


let xs = [2, 8]


let bs = Array(xs.lazy
  .map { double($0) }
  .filter { filter($0) }
)

print("result: \(bs)")

output

double 2
filter 4
double 8
filter 16
double 2
filter 4
double 2
double 8
filter 16
result: [4]

I've got the expected behavior in https://gist.github.com/yas375/e63416596701e6cece2e2158cc0b8c1d