// Program that utilises function pointer to perform mathematical operations.
//
// Written by YOUR-NAME (YOUR-ZID), DD-MM-YYYY
//

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

double (*get_operation_function(char operation))(double, double);
void perform_operation(
    double first,
    double second,
    double (*operation_function)(double, double)
);

// DO NOT CHANGE THIS MAIN FUNCTION
int main(void) {
    char operation;
    double first;
    double second;

    double (*operation_function)(double, double);

    printf("Please enter an operation: ");
    while (scanf(" %c", &operation) == 1) {
        operation_function = get_operation_function(operation);
        if (operation_function == NULL) {
            printf("Invalid operation '%c'\n", operation);
        } else {
            printf("Please enter 2 numbers to perform this operation on: ");
            scanf("%lf %lf", &first, &second);
            
            perform_operation(first, second, operation_function);
        }
        printf("Please enter an operation: ");
    }
}

// Given two numbers `a` and `b`, return the result of adding them
double addition(double a, double b) {
    return a + b;
}

// Given two numbers `a` and `b`, return the result of subtracting `b` from `a`
double subtraction(double a, double b) {
    return a - b;
}

// Given two numbers `a` and `b`, return the result of multiplying them
double multiplication(double a, double b) {
    return a * b;
}

// Given two numbers `a` and `b`, return the result of dividing `a` by `b`
double division(double a, double b) {
    return a / b;
}

// Given an `operation`, return a pointer to the function that can perform
// that operation.
//
// E.g. if addition is the operation, a pointer to the `addition` function
// should be returned.
double (*get_operation_function(char operation))(double, double) {
    // TODO: COMPLETE THIS FUNCTION & CHANGE THIS RETURN
    return NULL;
}

// Performs an operation given various amounts of information.
void perform_operation(
    double first,
    double second,
    double (*operation_function)(double, double)
) {
    // TODO: COMPLETE THIS FUNCTION
}