> map .elems, (collatz($_) for 1, 3 ... 10)
Cannot call map(Int, List); none of these signatures match:
    (&code, *@values is raw)
    (Whatever, \a)
    (&code, Whatever)
  in block <unit> at <unknown file>:1

> (.elems for (collatz($_) for 1, 3 ... 10))
(1 8 6 17 20)