public void Parse(ExpressionParserHelper parseHelper)
{
Token token = parseHelper.Current;
parseHelper.Expect(CONSTANT_SIGN);
parseHelper.Read(ConstantParser.CONSTANT_SIGN);
String constantStr = parseHelper.ReadUntil(TokenType.Seperator, ConstantParser.CONSTANT_SIGN);
parseHelper.Expect(ConstantParser.CONSTANT_SIGN);
var constant = new StringConstant(constantStr);
constant.Token = token;
parseHelper.Push(constant);
}