Vector iterator not dereferencable

Question

I have an abstract base class called Shape from which both Circle and Rectangle are derived, but when I execute the following code in VS 2005 I get the error Debug assertion

Answer 1

Like @David Pierre suggests: find is value-based: it looks in the range of iterators for a pointer (e.g. 0x0F234420) that equals the pointer to the new Circle(point(1,2),3) you just created. Since that's a new object, it won't be there.

You can get around this by using find_if with an operator that compares the objects referenced to by the pointer.

However, the Criterium should be able to differentiate between shape types.

class Shape {
public:
    //amongst other functions
    virtual bool equal( const Shape* ) const = 0;
};

class Circle : public Shape {
public:
    bool equal( const Shape* pOther ) const {
        const Circle* pOtherCircle = dynamic_cast( pOther );
        if( pOtherCircle == NULL ) return false;
        // compare circle members
    }
};

class Rectangle : public Shape {
public:
    bool equal( const Shape* pOther ) const {
        const Rectangle* pOtherR = dynamic_cast( pOther );
        if( pOtherR == NULL ) return false;
        // compare rectangle members
    }
};



Shape* pFindThis = new Circle(point(1,2),3);
vector::const_iterator itFound = find_if(s1.begin(),s1.end(), 
    bind1st( mem_fun( &Shape::equal ), pFindThis) ) );
delete pFindThis; //leak resolved by Mark Ransom - tx!

if( itFound != s1.end() ) {
    (*itFound)->move(point(10,20));
}