CODEWITHSUNDEEP
c++booleanprimes
TDNguyen
TDNguyen

Reputation: 23

Finding Prime Number: error: control reaches end of non-void function

I was coding to find the prime number and extract the result as a boolean (true/false or 1/0) using the below code.

#include <iostream>
using namespace std;

bool isPrimeNumber(int n) {
    int m, i;
    m = n / 2;
    for (i = 2; i < m; i++) {
        if (n % i == 0) {
            return true;
        } else {
            return false;
        }
    }
}
int main() {
    cout << isPrimeNumber(33);
    return 0;
}

(Here the result should be 0 since 67 is a prime number)

(I'm skipping negative numbers and 0,1, but I will add it later)

Then on line 9, it said "error: control reaches end of non-void function."

I tried to find the solution on the Internet, and of course, StackOverflow. But my code was still right and buildable.

I think it has something to do with treating warnings as errors (I changed it under recommendation as a beginner). But I don't wanna change it back since I'm still learning.

Do you have a way to solve this problem without changing my setup back to normal?

Upvotes: 1

Views: 140

Answers (1)

Somil Garg
Somil Garg

Reputation: 474

When n is odd you get the error :

error: control reaches end of non-void function.

You're checking divisibility of n by only one value i=2. You have to check for each value of i from 2 to m.

Return false after iteration of for loop is completed.
Change your isPrimeNumber() function as below:-

bool isPrimeNumber(int n){
int m,i;
m = n/2;
    for (i=2;i<m;i++){
      if (n % i == 0){
         return true;
      }
    }
 return false;
}

Upvotes: 2

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