How to determine if a string is a number with C++?

Question

I\'ve had quite a bit of trouble trying to write a function that checks if a string is a number. For a game I am writing I just need to check if a line from the file I am r

Answer 1

My solution using C++11 regex (#include ), it can be used for more precise check, like unsigned int, double etc:

static const std::regex INT_TYPE("[+-]?[0-9]+");
static const std::regex UNSIGNED_INT_TYPE("[+]?[0-9]+");
static const std::regex DOUBLE_TYPE("[+-]?[0-9]+[.]?[0-9]+");
static const std::regex UNSIGNED_DOUBLE_TYPE("[+]?[0-9]+[.]?[0-9]+");

bool isIntegerType(const std::string& str_)
{
  return std::regex_match(str_, INT_TYPE);
}

bool isUnsignedIntegerType(const std::string& str_)
{
  return std::regex_match(str_, UNSIGNED_INT_TYPE);
}

bool isDoubleType(const std::string& str_)
{
  return std::regex_match(str_, DOUBLE_TYPE);
}

bool isUnsignedDoubleType(const std::string& str_)
{
  return std::regex_match(str_, UNSIGNED_DOUBLE_TYPE);
}

You can find this code at http://ideone.com/lyDtfi, this can be easily modified to meet the requirements.