Constant Function Arguments
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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, you 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
1234567891011#include <iostream> double square(const double number) { return number * number; } int main() { std::cout << 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
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); return 0; // Invalid radius, return 0 } int main() { double radius = 5.0; double pi = 3.14159; double result = area(&radius, pi); std::cout << "Area of the circle with radius " << radius << " is: " << result << std::endl; }
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