c++ - go back to first instruction when there is an error -

i creating simple console application obtain user input integer.

i want condition should integer , should not more 3 , not less 0.

the code came far is:

#include <iostream> #include <sstream> #include <string> using namespace std;  int main() {      int uinval;      while (true) {         string tempoval;         cout << "please enter value between 0-3:\n>";         cin >> tempoval;          stringstream ss(tempoval);         if (ss >> uinval)         {             break;             cout << "entered invalid value";         }          while (true)         {             if (uinval < 0 || uinval > 3)                 break;             cout << "value must between 0-3";         }          cout << "you have entered:" << uinval;          return 0;     } 

this works when input non-integer value a,b,c,d. not work when input -1 or 4 value.

i not sure, maybe confused myself while loops.

this incorrect:

while(true){    if(uinval < 0 || uinval > 3)      break;      cout <<"value must between 0-3"; } 

you check condition on uinval repeatedly, without giving user chance enter new value.

to fix problem, remove second loop, , replace

if(ss >> uinval) {     break; } 

inside first loop with

if(ss >> uinval && uinval >= 0 && uinval < 4) {     break; }