Mutable members in const member functions still const

I´ve been trying to modify a data-member in const member function on a const object but I´ve been unsuccesful. I´ve been reading a book and found a code example on the net (http://cplus.about.com/library/gloss...ef-mutable.htm) on this subject, but still I can´t get it. Here is the code

Code:

---

#include <iostream>
#include <string>

using namespace std;

class Animal {
public:
    void setAge(int age);
        int getAge() const {return itsage;}
        Animal(string aname, string afood, int age);

private:
    string name;
    string food;
    mutable int itsage;

};

Animal::Animal(string aname, string afood, int age)
{
        name = aname;
        food = afood;
        itsage = age;
}

void Animal::setAge(int age)
{
        itsage = age;
}

int main()
{
    Animal Tiger(string("Tigerman"), string("Meat"), 8);
    //const Animal Tigermania(string("Tigermania"), string("moremeat"), 10);

    Tiger.setAge(90);
       
    cout << "Tigerman is " << Tiger.getAge() << " year(s) old" << endl;
   
return 0;
}

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A get a compiler-error on the line

Code:

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const Animal Tigermania(string("Tigermania"), string("moremeat"), 10);

---

Apperently I´m using it wrong because I´ve compiled it under two different compilers and get the same error.

Its a little perverse doing this IMO :)

Ok...to envoke this on a const object, you can make the setAge const (even though it is assigning to a mutable)...this will then allow the func to be envoked on a const object....

Code:

---

#include <iostream>
#include <string>

using namespace std;

class Animal {
public:
        void setAge(int age)const;
        int getAge() const {return itsage;}
        Animal(string aname, string afood, int age);

private:
    string name;
    string food;
    mutable int itsage;

};

Animal::Animal(string aname, string afood, int age)
{
        name = aname;
        food = afood;
        itsage = age;
}

void Animal::setAge(int age)const
{
        itsage = age;
}

int main()
{
    Animal Tiger(string("Tigerman"), string("Meat"), 8);
    const Animal Tigermania(string("Tigermania"), string("moremeat"), 10);

        cout << "Tiger is " << Tiger.getAge() << " year(s) old" << endl;
        cout << "Tigermania is " << Tigermania.getAge() << " year(s) old" << endl;
 

    Tiger.setAge(90);
        Tigermania.setAge(10);
   

    cout << "Tiger is " << Tiger.getAge() << " year(s) old" << endl;
        cout << "Tigermania is " << Tigermania.getAge() << " year(s) old" << endl;
 
return 0;
}

---

Hmm..seems to work...but I still see it as perverse :)

Quote:

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Its a little perverse doing this IMO
....
....
....
Hmm..seems to work...but I still see it as perverse

---

LOL :D, a little??? I know what you are meaning but I wanted to se if it was possible. But what is more perverse is how they could "forget" the const on http://cplus.about.com/library/gloss...ef-mutable.htm.

Just out of curiosity is the setAge function overloaded in this case??

Code:

---

void setAge(int age)const;
void setAge(int age);

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Depending if an object is const or not the "right" function is invoked. But if I recall it right, a fuction is only overloaded when the parameter list differs.

yes