/// pidgin C++

class A{
int foobar; ..

public:
foo () { bar().. }
bar () {..} // DOES has some contract..
};

class B : A {
public:
bar () { /* let's broke foo() - let's implement someth cruel here */ } // BROEKN bar's contract
}

B->foo () // THIS CALL can't guarantee A+B's INVARIANT [ A's one to be presice ]