// math.c - Demonstrates various symbol types and linkage

#include <stdio.h>

// Global symbols - exported (visible to other files)
int pi = 3;
int e = 2;

// Static global - local to this file only
static int randomval = 7;

// External declarations - symbols defined elsewhere
extern int usrid;

// Function definitions

// Global function - exported symbol
int square(int x) {
    return x * x;
}

// Static function - local to this file only
static int is_prime(int x) {
    if (x < 2) return 0;
    if (x == 2) return 1;
    if (x % 2 == 0) return 0;
    
    for (int i = 3; i * i <= x; i += 2) {
        if (x % i == 0) return 0;
    }
    return 1;
}

// Global function that uses static function
int pick_prime() {
    int candidate = randomval;
    while (!is_prime(candidate)) {
        candidate++;
    }
    return candidate;
}

// Function that references external symbol
int get_n() {
    return usrid;
}

// Function that demonstrates various symbol types
void show_values() {
    printf("Global symbols: pi=%d, e=%d\n", pi, e);
    printf("Static symbol used internally: randomval=%d\n", randomval);
    printf("External symbol: usrid=%d\n", usrid);
    printf("Function results: square(5)=%d, pick_prime()=%d\n", 
           square(5), pick_prime());
}