Question

Give the function header for each of the following functions: a) Function hypotenuse that takes two double-precision, floating-point arguments, side1 and side2, and returns a double-precision, floating-point result. b) Function smallest that takes three integers, x, y and z, and returns an integer. c) Function instructions that does not receive any arguments and does not return a value. [Note: Such functions are commonly used to display instructions to a user.] d) Function intToDouble that takes an integer argument, number, and returns a double- precision, floating-point result.

Short answer

a) double hypotenuse(double side1, double side2) b) int smallest(int x, int y, int z) c) void instructions() d) double intToDouble(int number)

Step-by-step solution

Function hypotenuse

To create the function header for the hypotenuse function, identify the return type, function name, and parameter types. The return type is a double-precision floating-point number. The name of the function is 'hypotenuse'. It takes two double-precision floating-point numbers as parameters. So, the header will be 'double hypotenuse(double side1, double side2)'.

Function smallest

For the smallest function, recognize the return type and the parameter types. Here, the function returns an integer, and it also takes three integers as parameters. The name of the function is 'smallest'. Therefore, the function header will be 'int smallest(int x, int y, int z)'.

Function instructions

The instructions function does not take any arguments and also does not return anything, hence 'void' is used as the return type to specify that no value will be returned. The header will simply be 'void instructions()'. This is typical for a function meant to display information.

Function intToDouble

The intToDouble function header needs a return type that is a double-precision floating-point number and one integer parameter. This tells us that the header will be 'double intToDouble(int number)'.

Key concepts

Function Prototypes

To understand how C++ function prototypes work, let's think of them as a sneak peek or a summary of what a function can do without actually seeing its inner workings. Similar to the contents page in a book, function prototypes give both the coder and the compiler a quick glimpse into the function's functionality. In essence, a function prototype outlines the function's name, its return type, and the parameters (or 'arguments') it takes, along with their data types.

For example, according to the textbook exercise, the function prototype for 'hypotenuse' is declared as 'double hypotenuse(double side1, double side2);'. This indicates to the compiler that there's a function called 'hypotenuse', it expects two double arguments, and it will return a double value. Prototypes are crucial in C++ programming because they inform the compiler about function calls before the actual function definition is encountered during the linking phase, thereby preventing any 'implicit declaration' errors.

Data Types

C++ is a strongly-typed language, which means that every variable and expression has a type, and that type is known at compile time. Data types in C++ define the type of data a variable can hold, such as integer, floating-point numbers, or characters, and also determine the kind of operations that can be performed on that data. The importance of data types is demonstrated in the step by step solutions where the 'smallest' function returns an integer and takes three integers as parameters, represented as 'int smallest(int x, int y, int z);'. The correct usage of data types is essential for the correctness, efficiency, and clarity of the code. It’s akin to choosing the right kind of storage container; choosing wrongly could either waste space (memory) or lead to content (data) spillage (errors or unintended behavior).

Function Declaration

When we define a function declaration, or more commonly 'function header', we're making a promise to the compiler about how a function will look and behave. This acts as a contract—or in programming terms, a prototype—that must be fulfilled later when the function is actually defined with the code that implements its behavior. The declaration includes the function's name, its return type, and the types of any parameters it accepts. Take 'void instructions()' as an example. Here, 'void' signifies that this function doesn't deliver a return value, and the empty parentheses indicate it doesn’t require any input parameters. To summarize, a function declaration is like an advertisement for a movie: It tells you the title and what to expect, but not the whole story—that’s reserved for the function's definition where the full code is written.