code: public Token scanSymbol() {
          int length = 0;
          while (CharType.isSymbol(charAt(offset + length))) {
              length++;
          }
          String literals = input.substring(offset, offset + length);
          Symbol symbol;
          while (null == (symbol = Symbol.literalsOf(literals))) {
              literals = input.substring(offset, offset + --length);
          }
          return new Token(symbol, literals, offset + length);
      }
docs: scan symbol.
  
  @return symbol token