In C++, a const member function is a function that guarantees not to modify any member variables of the class. It is intended to be called on const objects or through a reference to a const object.

A const member function can be declared in two ways:

1. Inside the class definition:

   class MyClass {
   public:
    void normalFunc(); // Non-const member function
    void constFunc() const; // Const member function
   };
   

2. Outside the class definition: ```cpp class MyClass { public: void normalFunc(); // Non-const member function void constFunc() const; // Const member function };

void MyClass::normalFunc() { // Implementation }

void MyClass::constFunc() const { // Implementation }

To call a `const` member function, you can use either an object or a reference to a `const` object as follows:

```cpp
MyClass obj1;
const MyClass obj2;

obj1.normalFunc(); // Calling non-const member function on non-const object
obj2.constFunc(); // Calling const member function on const object

const MyClass& ref = obj1;
ref.constFunc(); // Calling const member function through a reference to a const object

Keep in mind that if you try to call a non-const member function on a const object or through a reference to a const object, it will result in a compilation error.

By using const member functions, you can ensure that certain operations on objects do not modify their internal state. This allows for better code readability, maintainability, and also helps the compiler perform optimizations based on the const guarantees.

#C++ #ConstMemberFunctions