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Essentially, encapsulation prevents external code from being concerned with the internal workings of an object. Encapsulation allows developers to present a consistent interface that is independent of its internal implementation. As one example, encapsulation can be used to hide the values or state of a structured data object inside a class.
C++ uses the three modifiers called public, protected, and private. [3] C# has the modifiers public, protected,internal, private, protected internal, private protected, and file. [4] Java has public, package, protected, and private; package is the default, used if no other access modifier keyword is specified. The meaning of these modifiers may ...
For example, if a three-dimensional point (x, y, z) is represented in a program with three floating-point scalar variables and later, the representation is changed to a single array variable of size three, a module designed with information hiding in mind would protect the remainder of the program from such a change.
Because C++ templates are type-aware and Turing-complete, they can also be used to let the compiler resolve recursive conditionals and generate substantial programs through template metaprogramming. Contrary to some opinion, template code will not generate a bulk code after compilation with the proper compiler settings. [77]
The curiously recurring template pattern (CRTP) is an idiom, originally in C++, in which a class X derives from a class template instantiation using X itself as a template argument. [1] More generally it is known as F-bound polymorphism , and it is a form of F -bounded quantification .
For example, if a date is represented by separate private year, month and day variables, then incoming dates can be split by the setDate mutator while for consistency the same private instance variables are accessed by setYear and setMonth. In all cases month values outside of 1 - 12 can be rejected by the same code.
The C++ examples in this section demonstrate the principle of using composition and interfaces to achieve code reuse and polymorphism. Due to the C++ language not having a dedicated keyword to declare interfaces, the following C++ example uses inheritance from a pure abstract base class .
The use of templates as a metaprogramming technique requires two distinct operations: a template must be defined, and a defined template must be instantiated.The generic form of the generated source code is described in the template definition, and when the template is instantiated, the generic form in the template is used to generate a specific set of source code.