Differences with const keyword in C++

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Here’s the most const example:

class Foo
{
    const int * const get() const {return 0;}
    \_______/   \___/       \___/
        |         |           ^-this means that the function can be called on a const object
        |         ^-this means that the pointer that is returned is const itself
        ^-this means that the pointer returned points to a const int    
};

In your particular case

//returns some integer by copy; can be called on a const object:
int get() const {return x;}        
//returns a const reference to some integer, can be called on non-cost objects:
const int& get() {return x;}      
//returns a const reference to some integer, can be called on a const object:
const int& get() const {return x;}

This question explains a little more about const member functions.

Const references can also used to prolong the lifetime of temporaries.

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