Need help making this function using ONLY the following includes:

#include #include #include #include #include #include #include #include

using std::cin; using std::cout; using std::endl; using std::string; using std::getline; using std::ifstream; using std::invalid_argument;

Input will be a number defined as a string.

// // Name: is valid number // PreCondition: a string that needs to be checked as a valid competition Il number (non-negative int) // PostCondition: returns TRUE if string is only made up of numeric chars 0-9 //-- bool is_valid_number(const std::string& str) { - }