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Polymorphism can be distinguished by when the implementation is selected: statically (at compile time) or dynamically (at run time, typically via a virtual function). This is known respectively as static dispatch and dynamic dispatch, and the corresponding forms of polymorphism are accordingly called static polymorphism and dynamic polymorphism.
Since C++ does not support late binding, the virtual table in a C++ object cannot be modified at runtime, which limits the potential set of dispatch targets to a finite set chosen at compile time. Type overloading does not produce dynamic dispatch in C++ as the language considers the types of the message parameters part of the formal message name.
The concept of the virtual function solves the following problem: In object-oriented programming, when a derived class inherits from a base class, an object of the derived class may be referred to via a pointer or reference of the base class type instead of the derived class type.
The visitor code pattern is only aware of SHAPE and SURFACE generically and not of the specific type of either. Instead, the code relies on run-time polymorphism and the mechanics of agents to achieve a highly flexible co-variant relationship between these two deferred classes and their descendants.
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 .
As such, the compiler must also generate "hidden" code in the constructors of each class to initialize a new object's virtual table pointer to the address of its class's virtual method table. Many compilers place the virtual table pointer as the last member of the object; other compilers place it as the first; portable source code works either ...
Examples are templates in C++, and generic programming in Fortran and other languages, in conjunction with function overloading (including operator overloading). Code is said to be monomorphised , with specific data types deduced and traced through the call graph , in order to instantiate specific versions of generic functions , and select ...
In computing, late binding or dynamic linkage [1] —though not an identical process to dynamically linking imported code libraries—is a computer programming mechanism in which the method being called upon an object, or the function being called with arguments, is looked up by name at runtime.