Why does the pow function reduce the length of my loop in C

December 2, 2021

i have this code:

#include <stdio.h>
#include <math.h>
int check_menu(int menu1)
{
    if (menu1 > 3 || menu1 < 0)
        return 1;
    else
        return 0;
}

void menu()
{
    int choice, count = 0, count2;
    do {
        printf("----MENU----\n0 -> Exit\n1 -> Prime time\n2 -> Calander calculating\n3 -> Matrix printing\n");
        scanf_s("%d", &choice);
        count++;
        if (choice < 0 || choice > 3)
            printf("%d/5 errors\n", count);
    } while (check_menu(choice) == 1 && count <= 4);
    determine(choice);
}
int prime_check(int num) {
    int i, is_prime = 1;
    for (i = 2; i * i <= num; i++) {
        if (num % i == 0) {
            is_prime = 0;
        }
    }
    return is_prime;
}
void prime_total(int num) {
    int prime, germain, marsenne, couss, cousb, twins, twinb, fermat, loop, i;
    for (i = -9, loop = num - 9; loop <= num + 9; loop++, i++) {
        prime =prime_check(loop),germain=prime_check(2*loop+1),marsenne=prime_check(pow(2, loop)-1),twins=prime_check(loop+2),twinb=prime_check(loop-2),couss=prime_check(loop+4),cousb=prime_check(loop-4);// prime
        if (prime == 0)
            germain = 0, marsenne = 0, cousb = 0, couss = 0, twins = 0, twinb = 0, fermat = 0;
        printf("%3d)  %3d|%d|%d|%d|%d|%d|%d|%d|\n",i, loop, prime, germain, marsenne, twinb, twins, cousb, couss);
    }
    menu();
}
int Prime_time() {
    int num;
    do {
        printf("enter a number (1 - 1000000):\n");
        scanf_s("%d", &num);
    } while (num < 1 || num > 1000000);
    prime_total(num);
}

int determine(int choice) {
    if (choice == 1)
        Prime_time();
}
void main()
{
    menu();
}
}

the problem im having is with the prime_total function the thing is that whenever i use the pow function to pass a parameter to prime_check then it dosent call menu and gets stuck midway through the loop.
when i dont use pow then it works fine.

>Solution :

Your problem is in this piece of code:

void prime_total(int num) {
    int prime, germain, marsenne, couss, cousb, twins, twinb, fermat, loop, i;
    for (i = -9, loop = num - 9; loop <= num + 9; loop++, i++) {
        prime =prime_check(loop),germain=prime_check(2*loop+1),marsenne=prime_check(pow(2, loop)-1),twins=prime_check(loop+2),twinb=prime_check(loop-2),couss=prime_check(loop+4),cousb=prime_check(loop-4);// prime
        if (prime == 0)
            germain = 0, marsenne = 0, cousb = 0, couss = 0, twins = 0, twinb = 0, fermat = 0;
        printf("%3d)  %3d|%d|%d|%d|%d|%d|%d|%d|\n",i, loop, prime, germain, marsenne, twinb, twins, cousb, couss);
    }
    menu();
}

If you consider the manual page for the pow() function:

NAME
     pow -- power function

SYNOPSIS
     #include <math.h>

     double
     pow(double x, double y);

     long double
     powl(long double x, long double y);

     float
     powf(float x, float y);

Notice that int is not the type used in either calling or handling a return from any of these. In fact, by using pow() you are expecting a double as a return value.

To find these types of errors, you might consider compiling your code with: