void test1()
{  
std::string str1 = "1";

std::string str2 = "1.5";

std::string str3 = "1 with words";



int myint1 = std::stoi(str1);

int myint2 = std::stoi(str2);

int myint3 = std::stoi(str3);


std::cout << "std::stoi(\"" << str1 << "\") is " << myint1 << '\n';

std::cout << "std::stoi(\"" << str2 << "\") is " << myint2 << '\n';

std::cout << "std::stoi(\"" << str3 << "\") is " << myint3 << '\n';
}

std::stoi(“1”) is 1 
std::stoi(“1.5”) is 1 
std::stoi(“1 with words”) is 1

void test2()
{

 std::string str_dec = "2001, A Space Odyssey";
 std::string str_hex = "40c3";
 std::string str_bin = "-10010110001";
 std::string str_auto = "0x7f";

 std::string::size_type sz;  // alias of size_t

 int i_dec = std::stoi (str_dec,&sz);
 int i_hex = std::stoi (str_hex,nullptr,16);
 int i_bin = std::stoi (str_bin,nullptr,2);
 int i_auto = std::stoi (str_auto,nullptr,0);

 std::cout << str_dec << ": " << i_dec << " and [" << str_dec.substr(sz) << "]\n";
 std::cout << str_hex << ": " << i_hex << '\n';
 std::cout << str_bin << ": " << i_bin << '\n';
 std::cout << str_auto << ": " << i_auto << '\n';

 return 0;
}

2001, A Space Odyssey: 2001 and [, A Space Odyssey] 
40c3: 16579 
-10010110001: -1201 
0x7f: 127