#include <stdio.h>

/**
 * calculate the sum of two numbers
 * @param number1 first summand
 * @param number2 second summand
 * @return sum of the two summands
 */
int add(int number1, int number2);

/**
 * calculate the product of two numbers
 * @param number1 first factor
 * @param number2 second factor
 * @return product of the two factors
 */
float multiply(int number1, float number2);

/**
 * calculate the power of two integers
 * @param number1 basis
 * @param number2 exponent
 * @returns number1 to the power of number2
 */
int power(int number1, int number2);

/**
 * calculate the remainder of the division of two numbers
 * @param number1 divident
 * @param number2 divisor
 * @returns number1 modulo number2
 */
int modulo(int number1, int number2);

/**
 * calculate the factorial
 * @param number number to calculate factorial of
 * @return number!
 */
int factorial(int number);

/**
 * calculate a fibonacci number
 * @param number what fibonacci number should be computed?
 * @returns numberth fibonacci number
 */
int fib(int number);

int main(void) {
    int number1;
    int number2;
    char operator;

    printf("give me two numbers and an operator seperated by spaces\n");
    int n_matched = scanf("%d %c %d", &number1, &operator, &number2);

    if (n_matched != 3) {
        printf("Failure!\n");
        return 1;
    }

    switch (operator) {
        case '+':
        case 'a':
        case 'A':
            printf("%d\n", add(number1, number2));
            break;
        case '-':
        case 's':
        case 'S':
            printf("%d\n", add(number1, -number2));
            break;
        case '*':
        case 'm':
        case 'M':
            printf("%d\n", multiply(number1, number2));
            break;
        case '/':
        case 'd':
        case 'D':
            printf("%f\n", multiply(number1, 1.0 / number2));
            break;
        case '%':
        case 'r':
        case 'R':
            printf("%d\n", modulo(number1, number2));
            break;
        default:
            printf("are you stupid? thats not an operator!!!1\n");
            break;
    }

    return 0;
}

int add(int number1, int number2) {
    return number1 + number2;
}

float multiply(int number1, float number2) {
    /* recursive approach */
    if (number1 == 0) {
        return 0;
    }
    return number2 + multiply(number1-1, number2);

    /* looping approach */
    float multiple = 0;
    for (int i = 0; i < number1; ++i) {
        multiple += number2;
    }
    return multiple;

    /* trivial approach */
    return number1 * number2;
}

int power(int number1, int number2) {
    /* looping approach */
    int power_value = 1;
    for (int i = 0; i < number2; ++i) {
        power_value *= number1;
    }
    return power_value;

    /* recursive approach */
    if (number2 == 0) {
        return 1;
    }
    return multiply(number1,power(number1, number2 - 1));
}

int modulo(int number1, int number2) {
    return number1 % number2;
}

int factorial(unsigned number) {
    if (number == 0) {
        return 1;
    }
    return number * factorial(number - 1);
}

int fib(unsigned number) {
    if (number == 0) {
        return 0;
    }
    if (number == 1) {
        return 0;
    }
    if (number == 2) {
        return 1;
    }

    return fib(number - 1) + fib(number - 2);
}