Question

The following statement calls a function named half, which returns a value that is half that of the argument passed to it. Assume that result and number have both been defined to be double variables. Write the half function. result \(=\) half (number)

Short answer

Question: Write a function named "half" that takes a double as an argument and returns half of its value. Answer: To write the function "half", follow these steps: 1. Define the function with the syntax `double half(double number) { }`. 2. Inside the function, calculate half of the input number by dividing it by 2.0, and store the result in a variable named "half_number": `double half_number = number / 2.0`. 3. Return the value of "half_number" using the `return` statement: `return half_number`. The complete function will look like this: ```cpp double half(double number) { double half_number = number / 2.0; return half_number; } ```

Step-by-step solution

Define the function half with double as input

First, we need to define the function with the following syntax: ```cpp double half(double number) { } ``` This defines a function named "half" that takes one argument of type `double` called "number". The function will return a value of type `double` as well.

Calculate half of the input number

Inside the function, we will calculate half of the input number by dividing it by 2.0. We will store the result in a variable named "half_number". ```cpp double half_number = number / 2.0; ```

Return the result

The final step is to return the value of "half_number" as the output of the function. To do this, we simply use the `return` statement followed by the variable name. ```cpp return half_number; ```

Complete Function

Given the steps above, the complete "half" function should look like this: ```cpp double half(double number) { double half_number = number / 2.0; return half_number; } ``` Now, whenever the function is called with a double as input, `result = half(number)` will store the value of half the input number in the variable "result".

Key concepts

Function Return Types

In C++, functions are subroutines that perform a specific task and can return a value to the part of the code that called them. The type of value that a function returns is specified by the function's return type, which is declared before the function's name in its definition. In the case of the 'half' function, the return type is 'double'. This means that the function will return a floating-point number to the calling code.

It's essential to match the return type with the type of value the function actually returns to avoid type mismatch errors. Other common return types include 'int' for integers, 'char' for characters, 'bool' for boolean values, and 'void' if the function does not return any value.

Parameter Passing

Parameter passing is the act of giving inputs to a function so it can perform operations using those inputs. In C++, parameters are placed within the parentheses following the function's name. The 'half' function takes one parameter named 'number', with a double data type.

When you pass a parameter to a function, you can do it by value or by reference. Passing by value means that a copy of the actual parameter is made and passed to the function, which is what's happening with the 'half' function. This is a safe way to ensure that the original data is not unintentionally modified. However, passing by reference using pointers or reference operators can be more efficient for large data structures.

Arithmetic Operations

Arithmetic operations in C++ are the foundation for any mathematical computation in the language. They include addition (+), subtraction (-), multiplication (*), division (/), and modulus (%). The 'half' function demonstrates the use of the division operation. It divides the input 'number' by 2.0 to find half of its value.

It's important to use compatible data types for the operands in arithmetic operations to avoid unexpected behavior. Using a floating-point literal like 2.0 ensures that the division is performed in floating-point arithmetic to return a precise result for floating-point inputs.

Variable Assignment

Variable assignment in C++ involves setting a value to a variable. The '=' operator is used to assign the result of an expression to a variable. The operation 'double half_number = number / 2.0;' from the 'half' function shows how assignment works. Here, 'half_number' is the variable, and 'number / 2.0' is the expression whose result is being assigned to this variable.

Proper variable assignment is crucial for storing results that you may need to use multiple times in your code. It helps in making your code clean, readable, and efficient by avoiding redundant calculations.