I’ll take the risk of stating the obvious: You call the function, if it’s defined in the base class it’s automatically available in the derived class (unless it’s private). If there is a function with the same signature in the derived class you can disambiguate it by adding the base class’s name followed by two colons base_class::foo(…). … Read more
The two int variables are defined in the header file. This means that every source file which includes the header will contain their definition (header inclusion is purely textual). The of course leads to multiple definition errors. You have several options to fix this. Make the variables static (static int WIDTH = 1024;). They will … Read more
The clearest way to express polymorphism is via an abstract base class (or interface) This class is abstract because the goPee() method is not definable for Humans. It is only definable for the subclasses Male and Female. Also, Human is an abstract concept — You cannot create a human that is neither Male nor Female. It’s got … Read more
This is not a compiler error: the error is coming from the linker. After compilation, the linker will merge the object files resulting from the compilation of each of your translation units (.cpp files). The linker finds out that you have the same symbol defined multiple times in different translation units, and complains about it … Read more
Polymorphism is one of the tenets of Object Oriented Programming (OOP). It is the practice of designing objects to share behaviors and to be able to override shared behaviors with specific ones. Polymorphism takes advantage of inheritance in order to make this happen. In OOP everything is considered to be modeled as an object. This … Read more
Here is a quick example of a binary insert:
Short Answer Use $this to refer to the current object. Use self to refer to the current class. In other words, use $this->member for non-static members, use self::$member for static members. Full Answer Here is an example of correct usage of $this and self for non-static and static member variables: Here is an example of incorrect usage of $this and self for non-static and static member variables: Here is an example of polymorphism with $this for member functions: Here … Read more
More on sorting by keys.
Single Underscore Names, in a class, with a leading underscore are simply to indicate to other programmers that the attribute or method is intended to be private. However, nothing special is done with the name itself. To quote PEP-8: _single_leading_underscore: weak “internal use” indicator. E.g. from M import * does not import objects whose name starts with an … Read more
You forget the tricky 2nd difference between classes and structs. Quoth the standard (§11.2.2 in C++98 through C++11): In absence of an access-specifier for a base class, public is assumed when the derived class is declared struct and private is assumed when the class is declared class. And just for completeness’ sake, the more widely known difference between class and … Read more