Re: Liskov substitution principle
* Alex Blekhman:
"Alf P. Steinbach" wrote:
Any program using the derived class will then most likely
exhibit slightly different behavior, without the LSP being
broken in any way.
Will you be so kind as to explain how this "slightly different
behavior" doesn't break LSP:
[snipped code that breaks LSP, under reasonable assumptions]
That code indeed breaks the LSP, provided the asserting function
expresses a contract on the base class' member function.
Now consider
class Graphic
{
public:
// Draw a light gray filled rectangle as default.
virtual void drawAt( Canvas& c, Point const& where ) const;
};
class Circloid: public Graphic
{
public:
// A circle.
virtual void drawAt( Canvas& c, Point const& where ) const;
};
Cheers,
- Alf (laughing)
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