# Pastebin IRzmbFaz
import os, sets, strutils, streams

proc main() =
  if paramCount() != 2:
    echo "mydiff file1 file2"
    quit(1)

  var
    old_lines: HashSet[string] = initSet[string]()
    new_lines: HashSet[string] = initSet[string]()
    line: string

  var file1 = newFileStream(paramStr(1), fmRead)
  if isNil(fs):
    echo "Failed to open file: ", paramStr(1)
    quit(1)

  defer: file1.close()

  while file1.readLine(line):
    old_lines.incl(line)

  var file2 = newFileStream(paramStr(2), fmRead)
  if isNil(fs):
    echo "Failed to open file: ", paramStr(2)
    quit(1)

  defer: file2.close()

  while file2.readLine(line):
    new_lines.incl(line)

  let old_added = old_lines_set - new_lines_set
  let old_removed = new_lines_set - old_lines_set 

  for line in old_lines:
    if line in old_added:
      echo "-", line.strip()
    elif line in old_removed:
      echo "+", line.strip()

  for line in new_lines:
    if line in old_added:
      echo "-", line.strip()
    elif line in old_removed:
      echo "+", line.strip()

main()