Learn Constant Function Arguments | Function Arguments Specification

Definition

Constant arguments in a function indicate that the values passed to the function as parameters cannot be modified inside the function.

Pass const Arguments by Value

When a parameter is passed by value and declared as const, a copy of the value is made, and the function cannot modify that copy.

To declare the constant argument, yo have to use const keyword before the type specifier of the argument inside the signature of the function. The const keyword acts as a clarifier, showing that the function does not change the passed value.

main.cpp


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#include <iostream>

double square(const double number)
{
    return number * number;
}

int main()
{
    square(25);
}

The const qualifier ensures that the number parameter cannot be modified within the square() function, and we can be sure about the integrity of the copied data.

Pass const arguments by pointer/reference

Using const with pointers or references protects the original data from modification. Passing by pointer or reference saves memory, but const ensures the original value remains unchanged inside the function.

main.cpp


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#include <iostream>

// Function definition
double area(const double* radiusPtr, const double& pi) {
    // Check if the pointer and reference are not null
    if (*radiusPtr > 0)
        return pi * (*radiusPtr) * (*radiusPtr);
    else 
        return 0; // Invalid radius, return 0
}

int main() {
    double radius = 5.0;
    double pi = 3.14159;

    double area = calculateArea(&radius, pi);

    std::cout << "Area of the circle with radius " << radius << " is: " << area << std::endl;
}

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Section 2. Chapter 3

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Definition

Constant arguments in a function indicate that the values passed to the function as parameters cannot be modified inside the function.

Pass const Arguments by Value

When a parameter is passed by value and declared as const, a copy of the value is made, and the function cannot modify that copy.

main.cpp


              1234567891011
            
#include <iostream>

double square(const double number)
{
    return number * number;
}

int main()
{
    square(25);
}

The const qualifier ensures that the number parameter cannot be modified within the square() function, and we can be sure about the integrity of the copied data.

Pass const arguments by pointer/reference

main.cpp


              12345678910111213141516171819
            
#include <iostream>

// Function definition
double area(const double* radiusPtr, const double& pi) {
    // Check if the pointer and reference are not null
    if (*radiusPtr > 0)
        return pi * (*radiusPtr) * (*radiusPtr);
    else 
        return 0; // Invalid radius, return 0
}

int main() {
    double radius = 5.0;
    double pi = 3.14159;

    double area = calculateArea(&radius, pi);

    std::cout << "Area of the circle with radius " << radius << " is: " << area << std::endl;
}

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 3