cpp func as const

In C++, the const keyword is used to declare that a function does not modify the state of the object it is called on. When a member function is declared as const, it means that it can be called on both const and non-const objects, but it guarantees that it will not modify the state of the object.

Here are the steps to declare a function as const in C++:

1. Start with the function declaration or definition. For example, let's say we have a class called MyClass and we want to declare a member function called myFunction as const.

2. Add the const keyword after the closing parenthesis of the function parameters. For example:

void myFunction() const;

1. If the function is defined outside the class declaration, you need to include the class name before the function name and use the const keyword again. For example:

void MyClass::myFunction() const {
  // Function body
}

1. Inside the function body, you can only call other const member functions of the class, or member functions that are declared as const explicitly. You cannot modify the member variables of the class, unless they are declared as mutable.

Here's an example that demonstrates the use of const member functions in C++:

class MyClass {
public:
  void myFunction() const;
  int getValue() const;

private:
  int value;
};

void MyClass::myFunction() const {
  // Calling a const member function
  int val = getValue();

  // Cannot modify member variables
  // value = 10; // Error: Cannot modify a const member function
}

int MyClass::getValue() const {
  return value;
}

In this example, the myFunction member function is declared as const and it can be called on both const and non-const objects of MyClass. Inside the function body, we can only call other const member functions, like getValue, and we cannot modify the value member variable.

I hope this explanation helps! Let me know if you have any further questions.