code: function parseNumber (inp) {
      var res = "";
      if (inp.takeAPeek("-")) res += "-";
    
      var match = parseInteger(inp);
      if (match) res += match;
    
      match = parseFraction(inp);
      if (match) res += match;
    
      if (res && res !== "-") {
        match = parseExponent(inp);
        if (match) res += match;
      }
    
      if (res === "-") syntaxError(inp, "Expected number");
      return res || null;
    }
docs: Number Parsers --------------