Prime-Number Function - C++ Function

C++ examples for Function:Function Creation

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Description

Prime-Number Function

Demo Code

#include <iostream>
#include <cmath>           // Include because sqrt is called.
using namespace std;
// Function must be declared before being used.
bool prime(int n);
int main()/*from w  w  w. j  a  v a 2  s.  c  om*/
{
   int n = 0;
   // Set up infinite loop; break if user enters 0.
   // Otherwise, evaluate n for prime-ness.
   while (true) {
      cout <<"Enter num (0 = exit) and press ENTER: ";
      cin >> n;
      if (n == 0) {        // If user entered 0, EXIT
         break;
      }
      if (prime(n)) {      // Call prime(i)
         cout << n << " is prime" << endl;
      } else {
         cout << n << " is not prime" << endl;
      }
   }
   return 0;
}
// Prime-number function. Test divisors from 2 to sqrt of n. Return false if a divisor found; otherwise, return true.
bool prime(int n) {
   for (int i = 2; i <= sqrt(n); ++i) {
      if (n % i == 0) {   // If i divides n evenly,
         return false;    //  n is not prime.
      }
   }
   return true;   // If no divisor found, n is prime.
}

Result


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