collate-front-and-back-feed-scans

mod.nu

# "Zip"/collate an even number of items such that every other item is pulled from the back.
#
# This is appropriate for scans of a stack of documents that run all front sides, then all back
# sides.
#
# # Examples
@example "reorder page numbers from a feed scanner" { [1 3 4 2] | collate-front-and-back-feed-scans } --result [1 2 3 4]
export def "main" [
]: list<any> -> list<any> {
  mut input = $in
  mut output = []

  if ($input | length | $in mod 2) != 0 {
    error make {
      msg: "provided list's length is not divisible by 2"
      label: {
        span: (metadata $input).span
      }
    }
  }

  while ($input | is-not-empty) {
    let front = $input | first --strict
    let back = $input | last --strict
    $output = $output | append [$front, $back]
    $input = $input | slice 1..-2
  }

  $output
}