Question

Write a complete \(\mathrm{C}_{+}+\) program with the two alternate functions specified below, each of which simply triples the variable count defined in main. Then compare and contrast the two approaches. These two functions are a) function tripleByvalue that passes a copy of count by value, triples the copy and returns the new value and a) function tripleByReference that passes count by reference via a reference parameter and triples the original value of count through its alias (i.e., the reference parameter).

Short answer

tripleByValue returns a tripled value without changing the original variable, while tripleByReference triples the original variable in place.

Step-by-step solution

Starting the program and the main function

Begin by setting up the basic structure of a C++ program. Include required headers and declare the main function. Initialize the 'count' variable in main.

Defining tripleByValue function

Define the function tripleByValue, which takes an int parameter and returns an int. This function should take the argument value, triple it, and return the new value.

Defining tripleByReference function

Define the function tripleByReference, which takes an int reference parameter. This function should triple the original value that the reference points to.

Using the functions in main

In the main function, call the tripleByValue function and display the result. Then, call tripleByReference function and display the updated 'count' variable.

Completing the main function

After calling the functions, add statements to conclude the main function. This includes returning 0 to indicate successful program termination.

Compiling and running the program

Compile the C++ program using a compiler. Check for any errors and warnings, then run the executable to see the program in action.

Comparing the two approaches

After running the program, notice the difference in functionality between the two functions: tripleByValue does not alter the original 'count' variable but returns the tripled value, while tripleByReference directly modifies the original 'count' variable, tripling its value.

Key concepts

Function Parameters in C++

In C++, function parameters are a fundamental concept that can significantly impact how a program operates. When you define a function, you can choose to pass arguments to it in two primary ways: by value or by reference. This choice dictates whether the function can modify the original data or only work with a copy of it.

Passing parameters by value means that a copy of the actual data is handed to the function, allowing the function to work on this copy without affecting the original variable. Conversely, passing parameters by reference means the function receives a reference to the actual data, giving it the ability to modify the original variable. This distinction is crucial when determining whether a function should alter the state of its input parameters or simply use their values for computation.

Reference Parameters

When you pass arguments by reference in C++, you are essentially passing the address of the variable, which means the function can directly access and modify the original data. It is done by using an ampersand (&) in the parameter declaration of the function.

Reference parameters are quite powerful, as they allow a function to change the value of the arguments passed to it. Because of this, they are often used when large data structures need to be modified or when a function needs to return multiple values. However, care must be taken because careless use can lead to bugs that can be hard to track down since multiple functions can alter the data.

Value Parameters

Value parameters in C++ work by creating a new copy of the variable passed to the function. This isolate's the function's operations from the original value, making it safe from unintended changes. When a variable is passed by value, the modifications made to the parameter within the function do not reflect back to the original data.

This approach is generally preferred when the function does not need to modify the original variable or when the safety of the original data is paramount. It ensures that the function's operations do not have side effects outside of its scope, which aids in maintaining code integrity and predictability. Moreover, passing by value can be less efficient if the data being passed is large since it involves creating a copy.

C++ Function Overloading

Function overloading in C++ is a feature that allows you to have more than one function with the same name, yet with different parameters (either in number, type, or both). The compiler distinguishes these functions by their signatures. This way, you can design your function to handle different data types or operations while maintaining a consistent function name.

For instance, you could have a function called 'process' that takes an integer and another 'process' function that takes a floating-point number. The appropriate function is called based on the argument's data type passed when the function is invoked. Function overloading makes your programs easier to read and maintain but requires careful planning to prevent confusion over which function is actually being called.

Program Execution in C++

Program execution in C++ is the process where the source code you write is compiled into machine code that the computer can run. This execution involves compiling, linking, and then running the program. Each function and operation in the code plays a role in how the program behaves.

Understanding the execution flow, including how functions receive and utilize their parameters, is essential to writing effective C++. You must consider the scope (where variables can be accessed), the lifetime (how long variables persist), and how functions interact with each other. In the context of passing parameters, whether by value or reference, it affects how variables are modified or accessed throughout the program's execution, thus influencing the program's overall behavior and efficiency.