read a file with nim line by line

readfile.nim

proc readwholefile() = 
  let data = readFile("data.txt")
  echo(data)

proc justoneline() =
  let f = open("data.txt")
  defer: f.close()

  let firstline = f.readLine()
  echo(firstline)


proc testreads() =
  let f = open("data.txt")
  defer:
    f.close()

  var ll = f.read_line()
  echo(ll)
  ll = f.read_line()
  echo(ll)
  ll = f.read_line()
  echo(ll)
  ll = f.read_line()
  echo(ll)

proc testfor() =
  let f = open("data.txt")
  defer: f.close()
  var line : string
  while f.read_line(line):
    echo(line)

proc testcustom_iter1() = 
  type
    CustomFile = object
      name : string
      inf : File

  iterator items(range: CustomFile): string  =
    var line : string
    while range.inf.read_line(line):
      yield line

  var inf : CustomFile
  inf = CustomFile(name : "data.txt",
    inf : open("data.txt"))
  for s in items(inf):
    echo(s)

proc test_iter2() = 
  iterator fitems(name : string) : string = 
    let f = open(name)
    defer: f.close()
    var line : string
    while f.read_line(line):
      yield line

  for s in fitems("data.txt"):
    echo("s",s)

proc test_iter3 =
  iterator `$`(filename : string) : string =
    let f = open(filename)
    defer:
      f.close()
    var line : string
    while f.read_line(line):
      yield line

  for line in $("data.txt"):
    echo(line)