What does mean the public keyword?

[h4ever]

Hi, I read the tutorials about classes but this convention is not clear to me:

That does mean the public Link after class ColorLink :
?

class ColorLink : public Link
{
public:
	long ref;
};

Note Link is class defined in code.

[The illusionist mirage]

Look up section of Inheritance from the book/tutorials you're following. It tells the compiler that the class ColorLink 'inherits' publicly from the existing class Link.

[keskiverto]

http://www.cplusplus.com/doc/tutorial/inheritance/

Link is a public base of ColorLink. Alternatives are protected and private base.

[Catfish666]

It specifies the inheritance type. In your example, public says how ColorLink can access member data of Link.

http://www.cplusplus.com/doc/tutorial/inheritance/#inheritance
http://publib.boulder.ibm.com/infocenter/cellcomp/v101v121/topic/com.ibm.xlcpp101.cell.doc/language_ref/cplr130.html

[keskiverto]

public says how ColorLink can access member data of Link.

No. ... how the user of ColorLink can access members of ColorLink that actually members of the base

[h4ever]

Oh, thanks. I'm surpised so many replies here. I found one more interesting declaration

class unit_in_rect : public std::unary_function<const Unit, bool>

I've found:
http://en.cppreference.com/w/cpp/utility/functional/unary_function
hm, but that looks hard to understand even I learned about the templates.

[keskiverto]

It is in no way different. ColorLink and unit_in_rect are deriving classes.
Link and std::unary_function<const Unit, bool> are base classes.
std is a namespace.
unary_function is a template for a class.

[h4ever]

Is this right?

A) PUBLIC
class derived_class_name: public base_class_name
derived_class_name will inherit protected, private, public members

B) PRIVATE
class derived_class_name: private base_class_name
derived_class_name will inherit members protected, private ... Member public is not accessible in the class / instance.

C) PROTECTED
class derived_class_name: public base_class_name
derived_class_name will inherit member protected only. Members private and public are not accessible in the class / instance.

[Catfish666]

Is this right?

No. Hopefully the pseudocode thing below will help:

class Base
{
private: A

protected: B

public: C
};

class Derived: private Base
{
private: B, C
};

class Derived: protected Base
{
protected: B, C
};

class Derived: public Base
{
protected: B

public: C
};

As you can see, users of Derived can never access private members of Base, no matter what kind of inheritance is used.

As for B and C they get "inserted" in the Derived class as shown above.

[h4ever]

Catfish666:
Thanks, I see now:

1) private members are not inherited at all
2) protected members and public members are degraded to private level if :private is used (and these are inherited).
3) protected members stays protected, but public members are degraded to protected level when :protected is used (and these are inherited)
4) when :public is used, then protected stays protected and public stays public (and these are inherited).