CPE 101 Chapter 4
Issue: How to create a reusable function that makes a decision


"Not So Good" - Procedure (void function)

void isEven(int number)
{
    if (number % 2 == 0)
    {
        printf("Number is even.");
    }
    else
    {
        printf("Number is odd.");
    }
}


"Better" - boolean function

int isEven(int number)
{
    return (number % 2 == 0);
}

int main(void)
{
    int someNumber = 3;
    if (isEven(someNumber))
    {
        printf("Number is even.");
    }
    else
    {
        printf("Number is odd.");
    }
}

    
This solution is more flexible because 
the decision logic is separate from the printing. 
Thus isEven() can be reused for different purposes than printing.



"Best" - boolean function with enum type

/* Logical (boolean) type */
typedef enum
{ false, true }
boolean;

boolean isEven(int number)
{
    return (number % 2 == 0);
}

int main(void)
{
    int someNumber = 3;
    if (isEven(someNumber))
    {
        printf("Number is even.");
    }
    else
    {
        printf("Number is odd.");
    }
}

    
This solution improves readability by using a
named type "boolean" to represent boolean functions
and make them easier to identify and distinguish
from functions that return integers.