string c++ substr
#include <string>
#include <iostream>
int main()
{
std::string a = "0123456789abcdefghij";
// count is npos, returns [pos, size())
std::string sub1 = a.substr(10);
std::cout << sub1 << 'n';
// both pos and pos+count are within bounds, returns [pos, pos+count)
std::string sub2 = a.substr(5, 3);
std::cout << sub2 << 'n';
// pos is within bounds, pos+count is not, returns [pos, size())
std::string sub4 = a.substr(a.size()-3, 50);
// this is effectively equivalent to
// std::string sub4 = a.substr(17, 3);
// since a.size() == 20, pos == a.size()-3 == 17, and a.size()-pos == 3
std::cout << sub4 << 'n';
try {
// pos is out of bounds, throws
std::string sub5 = a.substr(a.size()+3, 50);
std::cout << sub5 << 'n';
} catch(const std::out_of_range& e) {
std::cout << "pos exceeds string sizen";
}
}