anchor.diff:  // prints out the rendered characters (ignoring colors and attributes).
   // This is probably most useful when stdin/stdout are redirected from/to files.
   
  +import 'dart:convert';
   import 'dart:core';
   import 'dart:io';
   
  
positive.code: void printUsage(String argv0) {
    stdout.write('usage: $argv0 [option]... [--] (FILE|-)...\n\n'
                 '(- indicates standard input)\n');
  }
  
  void main(List<String> arguments) {
  
negative.code:   for (int i = first_file; i < arguments.length; i++) {
      if (arguments[i] == '-') {
        while (true) {
          var c = stdin.readByteSync();
          if (c < 0) {
            break;
          }
  