Issue with C++ constructor -

edit: question came , think aced it! go stackoverflow!! :d

i have exams coming up, , 1 of questions on last year's exams spot problem implementation of following constructor , write corrected one.

rectangle::rectangle(string col, int len, int br) {     setcolour(col);     length =len;     breadth=br; } 

the class definitions follows:

class polygon { public:     polygon(string col="red");     void printdetails(); // prints colour     virtual double getarea()=0;     void setcolour(string col); private:     string colour; };   class rectangle : public polygon { public:     rectangle(string, int, int);     void printdetails(); // prints colour , area     // part 3, delete line below     double getarea(); private:     int length;     int breadth; }; 

i've written code compiler , runs fine. i'm guessing question relating inheritance, since string colour; private, setcolour public cant figure out. unless rectangle::rectangle(string col, int len, int br):length(len), breadth(br) , set colour inside construcor or something.

its worth 3 marks not big deal if nobody wants answer, figure if i'm going have career programmer, in interest know as possible. ;)

thanks help.

ps, see getarea() in rectangle. when remove tells me "cannot instantiate abstract class". mean?

edit: here's main:

void main (void) {     rectangle rect1 ("blue",5,6);     rectangle *prect2 = new rectangle("red",5,6);     rect1.setcolour("red");     rect1.printdetails();     prect2->printdetails(); } 

i don't see wrong, though make more efficient using initialization list (otherwise private members of both classes initialized twice):

rectangle::rectangle(string col, int len, int br)  : polygon(col), length(len), breadth(br) {  } 

notice initialization list can call constructor of polygon well.

see why should prefer use member initialization list? complete description of advantages of using initialization lists.