type
  Span[T] = object
    data: ptr T
    length: int

func newSpan[T](data: ptr T, length: int): Span =
  return Span[T](data, length)

template `len`[T](span: Span): int =
  span.length

func `[]`[T](span: Span[T]; idx: SomeInteger): T =
  when not defined(danger):
    if(idx < 0 or idx >= span.length):
      raise newException(IndexDefect, "Index not in 0.." & (span.length - 1))
  return span.data[idx]

proc `[]=`[T](span: Span[T]; idx: SomeInteger, value: T) =
  when not defined(danger):
    if(idx < 0 or idx >= span.length):
      raise newException(IndexDefect, "Index not in 0.." & (span.length - 1))
  span.data[idx] = T
# Way better