Question

Write a function definition for a function called even that takes one argument of type \(i n t\) and returns a bool value. The function returns true if its one argument is an even number; otherwise, it returns false.

Short answer

Question: Write a function called "even" that takes an integer as an argument and returns a boolean value. The function should return true if the integer is even and false otherwise.

Step-by-step solution

Write the function signature

To begin, write the function signature which includes the function's name `even`, the input argument `int` for the integer, and `bool` as the return type for the function. ```cpp bool even(int num); ```

Implement the function body

Inside the function, use an if statement to check if the integer `num` is even. If it is (i.e., `num % 2 == 0`), return `true`. Otherwise, return `false`. Here's the complete function implementation: ```cpp bool even(int num) { if (num % 2 == 0) { return true; } else { return false; } } ```

Alternate Implementations

As an alternative, you can also use a ternary operator instead of the if-else statement to make the function shorter and more concise: ```cpp bool even(int num) { return (num % 2 == 0) ? true : false; } ``` Or even more simply, just return the result of the expression since it is a boolean value: ```cpp bool even(int num) { return num % 2 == 0; } ``` With these implementations, the `even` function checks if the input integer is even and returns the corresponding boolean value.

Key concepts

Function Definition

In C++, a function definition provides the complete body of a function including what the function does. It begins with a function header or signature that includes essential components such as the function’s name, return type, and parameters. Taking the example from the problem, to define a function called `even`, you begin by specifying the return type `bool`, indicating that the function will return a boolean value.
The function name `even` follows, which describes its purpose. Finally, in the parentheses, a parameter `int num` is placed, which means the function takes an integer as input. Hence, the function signature is `bool even(int num);`.
This signature tells the compiler what type of data is expected to be received and what type of data will be returned. It acts as a bridge between calling a function and writing it to perform specific actions. Once the function header is set, you proceed to implement the logic inside its curly braces.

Conditional Statements

Conditional statements in C++ allow you to perform different actions based on different conditions. They are a crucial part of controlling the flow of execution in a program. In this exercise, the function uses an `if-else` statement to determine if the number `num` is even.
Here's how it works:

• The `if` keyword is followed by a condition inside parentheses, `num % 2 == 0`. This condition checks if the remainder of dividing `num` by 2 is zero, which means the number is even.
• If the condition evaluates to true, the block of code immediately following the `if` statement is executed, returning `true`.
• Otherwise, the code block following the `else` keyword is executed, returning `false`.

These statements help programmers make decisions based on variable values or other conditions. By using conditional statements, complex logic can be broken down into simpler, easily understood steps, allowing computers to choose different execution paths.

Return Types

Return types in C++ specify what kind of value a function will return to its caller. When defining a function, its return type is declared at the very beginning of the function signature.
In this exercise, the return type is `bool`, meaning the function `even` must return a boolean value—either `true` or `false`.
Understanding return types is crucial because it greatly influences how the function is used and integrated with other parts of a program. They ensure that the function provides the correct type of data that the rest of the program can use. To illustrate further:

• If a function is supposed to perform a calculation and give back a number, you'd use `int` or `double` as its return type.
• For a function like `even`, where the main task is to verify a condition, a `bool` is ideal.
• If no data needs to be returned, a function might use `void` as its return type, indicating it performs its task without providing feedback to the caller.

Return types help maintain type safety in programs and prevent errors that might arise from unexpected data being passed around.