constants in c++ code example
Example 1: const in c++
// various versions of const are explained below
#include <iostream>
class Entity {
private:
int m_X, m_Y;
mutable int var; // can be modified inside const menthods
int* m_x, *m_y;// * use to create pointer in one line
public:
int GetX() const // cant modify class variables
{
//m_X = 4;//error private member can't be modified inside const method
var = 5; // was set mutable
return m_X;
}
int Get_X()// will modify class
{
return m_X;
}
const int* const getX() const // returning a pointer that cannot be modified & context of pointer cannot be modified
{
//m_x = 4;
return m_x;
}
void PrintEntity(const Entity& e) {
std::cout << e.GetX() << std::endl;
}
};
int main() {
Entity e;
const int MAX_AGE = 90;
// MAX_AGE =100; error const var is stored in read only section in memory and we can't write to that memory
// int const* a = new int; is same as const int* a = new int ;////but you can't change the context of pointer but can reassign it to a pointer something else
int * const a = new int; //can change the context of pointer but can't reassign it to a pointer something else
*a = 2;
a = &MAX_AGE;// error can't change it to ptr something else
std::cout << *a << std::endl;
a =(int*) &MAX_AGE;
std::cout << *a << std::endl;
}
Example 2: c++ constant
#define LENGTH 10
#define WIDTH 5
#define NEWLINE '\n'