const keyword

Three const placement: 1.

Using const member functions provides the following benefits:

• It enables the usage of the member function on const objects, allowing you to invoke the function without the risk of unintended modification of the object’s state.
• It allows the compiler to enforce the immutability of the object within the function, preventing accidental modifications.
• It provides clarity to the code readers that the member function does not modify the object.

In the given example, the operator- function is marked as const because it performs a subtraction operation between two Rational objects but does not modify the current object.