Use varargs for even more awesomeness!

transpose.nim

iterator transpose[T](groups: seq[seq[T]]): seq[T] =
  let maxLen = groups[0].len - 1
  for i in 0..maxLen:
    var selection: seq[T] = @[]
    for group in groups:
      selection.add(group[i])
    yield selection

when isMainModule:
  var foo = @[@[1,2,3,4],@[5,6,7,8],@[9,10,11,12]]
  for z in transpose(foo):
    echo(repr(z))