// Public domain / CC0. Use freely for any purpose. RoyR 2026
// calculator.cm - Simple expression calculator
// Demonstrates: global variables, function composition, control flow

void printf(uint8 *fmt);

// Global state for the calculator
int32 last_result = 0;
int32 operation_count = 0;

int32 add(int32 a, int32 b) {
    operation_count = operation_count + 1;
    last_result = a + b;
    return last_result;
}

int32 subtract(int32 a, int32 b) {
    operation_count = operation_count + 1;
    last_result = a - b;
    return last_result;
}

int32 multiply(int32 a, int32 b) {
    operation_count = operation_count + 1;
    last_result = a * b;
    return last_result;
}

int32 divide(int32 a, int32 b) {
    if (b == 0) {
        printf("Error: Division by zero\n");
        return 0;
    }
    operation_count = operation_count + 1;
    last_result = a / b;
    return last_result;
}

int32 power(int32 base, int32 exp) {
    operation_count = operation_count + 1;
    int32 result = 1;
    for (int32 i = 0; i < exp; i = i + 1) {
        result = result * base;
    }
    last_result = result;
    return result;
}

int32 factorial(int32 n) {
    operation_count = operation_count + 1;
    if (n <= 1) {
        last_result = 1;
        return 1;
    }
    int32 result = 1;
    for (int32 i = 2; i <= n; i = i + 1) {
        result = result * i;
    }
    last_result = result;
    return result;
}

void print_stats(void) {
    printf("\n=== Calculator Statistics ===\n");
    printf("Total operations: %d\n", operation_count);
    printf("Last result: %d\n", last_result);
    printf("============================\n");
}

int32 main(void) {
    printf("Calculator Demo\n");
    printf("===============\n\n");
    
    // Basic arithmetic
    printf("10 + 5 = %d\n", add(10, 5));
    printf("10 - 5 = %d\n", subtract(10, 5));
    printf("10 * 5 = %d\n", multiply(10, 5));
    printf("10 / 5 = %d\n", divide(10, 5));
    
    // Power function
    printf("\n2^10 = %d\n", power(2, 10));
    printf("5^3 = %d\n", power(5, 3));
    
    // Factorial
    printf("\n5! = %d\n", factorial(5));
    printf("10! = %d\n", factorial(10));
    
    // Complex expression: (5 + 3) * (10 - 2)
    int32 a = add(5, 3);
    int32 b = subtract(10, 2);
    int32 result = multiply(a, b);
    printf("\n(5 + 3) * (10 - 2) = %d\n", result);
    
    // Division by zero test
    printf("\nTesting division by zero:\n");
    divide(10, 0);
    
    print_stats();
    
    return 0;
}