Prime Numbers Exercise - Loop Issue C++ -

i trying solve exercise written in stroustrup's book calculating , printing if number between 1 , 100 prime number or not.

my code seems work but, when prints values on screen, starts 6 , not 2.

i have tried figure out why not able understand reason of that.

can lend me hand?

thank much!

 // prime numbers.cpp : definisce il punto di ingresso dell'applicazione console. //  #include "stdafx.h" #include "std_lib_facilities.h"  vector<int> primes = { 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97 };  int primecheck(int x) {      (int : primes) {         if (x <= primes[i])             break;         if (primes[i] == x)             return 1;         while (x % primes[i] != 0) {             --i;             if (i < 0) {                 return 1;                 break;             }             else {                 if (x % primes[i] == 0)                 return 2;             }         }     } }   int _tmain(int argc, _tchar* argv[]) {     (int = 1; <= 100; ++i) {         if (primecheck(i) == 1) {             cout << << " prime number." << endl;         }         else {             if (primecheck(i) == 2) {                 cout << << " not prime number." << endl;             }         }     }      keep_window_open();      return 0; } 

your code wrong , should rewrite it. not paths have return statement , must use instead of prime[i]

there's simple working code:

int primecheck(int x) {      (int prime : primes) {        if (x < prime) {           return 2;       }else if (x == prime) {         return 1;     }      return 2; }