function lex()

in lib/ace/mode/lua/luaparse.js [498:572]
55 lines of code
50 McCabe index (conditional complexity)

  function lex() {
    skipWhiteSpace();

    // Skip comments beginning with --
    while (45 === input.charCodeAt(index) &&
           45 === input.charCodeAt(index + 1)) {
      scanComment();
      skipWhiteSpace();
    }
    if (index >= length) return {
        type : EOF
      , value: '<eof>'
      , line: line
      , lineStart: lineStart
      , range: [index, index]
    };

    var charCode = input.charCodeAt(index)
      , next = input.charCodeAt(index + 1);

    // Memorize the range index where the token begins.
    tokenStart = index;
    if (isIdentifierStart(charCode)) return scanIdentifierOrKeyword();

    switch (charCode) {
      case 39: case 34: // '"
        return scanStringLiteral();

      // 0-9
      case 48: case 49: case 50: case 51: case 52: case 53:
      case 54: case 55: case 56: case 57:
        return scanNumericLiteral();

      case 46: // .
        // If the dot is followed by a digit it's a float.
        if (isDecDigit(next)) return scanNumericLiteral();
        if (46 === next) {
          if (46 === input.charCodeAt(index + 2)) return scanVarargLiteral();
          return scanPunctuator('..');
        }
        return scanPunctuator('.');

      case 61: // =
        if (61 === next) return scanPunctuator('==');
        return scanPunctuator('=');

      case 62: // >
        if (61 === next) return scanPunctuator('>=');
        return scanPunctuator('>');

      case 60: // <
        if (61 === next) return scanPunctuator('<=');
        return scanPunctuator('<');

      case 126: // ~
        if (61 === next) return scanPunctuator('~=');
        return scanPunctuator('~');

      case 58: // :
        if (58 === next) return scanPunctuator('::');
        return scanPunctuator(':');

      case 91: // [
        // Check for a multiline string, they begin with [= or [[
        if (91 === next || 61 === next) return scanLongStringLiteral();
        return scanPunctuator('[');

      // \* / ^ % , { } ] ( ) ; # - +
      case 42: case 47: case 94: case 37: case 44: case 123: case 125:
      case 93: case 40: case 41: case 59: case 35: case 45: case 43: case 38: case 124:
        return scanPunctuator(input.charAt(index));
    }

    return unexpected(input.charAt(index));
  }