/* CSE 351 Section 03
 *
 * calculator.c
 *
 * Provide two operands and an operator, and this program will print the
 * output of that operation.
 *
 * Usage: ./calculator, then use stdin to provide integer, integer, operator 
 *        arguments when the program prompts for them.
 *        Operator can be one of [+,-,/,x,%] and the operands are integers
 *
 * Notes:
 * 
 * => scanf() is used to take in arguments, read more on the documentation here:
 *    => http://en.cppreference.com/w/cpp/io/c/fscanf
 *    => http://www.cplusplus.com/reference/cstdio/scanf/?kw=scanf
 *
 * => function prototype above main() tells compiler the return type and params of print_operation()
 *    => could have also just declared the entire function above main()
 *    => neglecting to do either will result in a compilation error
 *
 * => this program does not rigorously check for input errors nor does it hand exceptions
 *
 */

#include <stdio.h>
#include <stdlib.h>

void print_operation(int a, int b, char operator);

int main(int argc, char **argv)
{
    /* scanf() takes in arguments from stdin and stores them according to the parameter
     * format in the locations pointer to by additional arguments.
     * The additional arguments should point to already allocated objects of the type 
     * specified by their corresponding format specifier within the format string.
     * */

    // Set up argument locations
    int a;
    int b;
    char operator[1];

    printf("num 1: ");
    scanf("%d", &a);  /* <-- %d is format, &a is location. */

    printf("num 2: ");
    scanf("%d", &b);

    printf("operator: ");
    scanf(" %c", operator);  /* <-- space in front of %c is important*/

    print_operation(a, b, operator[0]);

    return 0;
}

/* Prints out the result when the operator is applied to the 
 * operands a and b. Supports addition (+), subtraction (-),
 * division (/), multiplication (x), and modulus (%) */
void print_operation(int a, int b, char operator)
{
    int result = 0;
    switch (operator)
    {
        case '+':
            result = a + b;
            break;
        case '-':
            result = a - b;
            break;
        case '/':
            result = a / b;
            break;
        case 'x':
            result = a * b;
            break;
        case '%':
            result = a % b;
            break;
        default:
            printf("Invalid operator");
            return;
    }
    printf("%d %c %d = %d\n", a, operator, b, result);
}