c++ - Making Conditional isdigit() -

first @ code:

#‎include‬ <iostream> #include <ctype.h> using namespace std; int main() {     int a,b;     cout << "enter 2 digits" << endl;     cin >> >> b;     if (isdigit(a))         if (isdigit(b))             cout << a+b << endl;         else             cout << "invalid digit";     return 0; } 

so type output blank space. want print if user hit non digit or alpha program should display invalid string or if user hit digit must show sum of 2 digits

since you're reading int variables, enter has integers or input operator fail. if want read characters , check if digits, should read char variables, , need convert them proper integer values before operating on them.

try like:

inline int to_int(const char ch) {     return ch - '0'; }  // ...  char a, b; if (std::cin >> >> b) {     if (std::isdigit(a) && std::isdigit(b))         std::cout << to_int(a) + to_int(b) << '\n';     else         std::cout << "one not digit\n"; } else     std::cout << "error in input\n"; 

---

if want input 2 generic integer values, you're on right track, need make sure input okay:

int a, b; if (std::cin >> >> b)     std::cout << + b << '\n'; else     std::cout << "error in input (most not integers in input)\n";