Any mechanism that could result in different machine code for the operation being invoked involving "x", where the reason relates specifically to the run-time type of "x", is getting pretty close to run-time polymorphic, but there's one final issue: was that branching decided implicitly by the language, or arranged explicitly by the programmer? In the case of virtual dispatch, the compiler implicitly knows to create the virtual dispatch tables and lookups that branch to the type-appropriate code.
But, say we have a function pointer that was previously set to address type-appropriate code, or a type-specific number or enum that is used to control a switch to a type-specific case. These functionally achieve the same behaviour as run-time virtual dispatch, but the set up had to be done explicitly by the developer, and there's no compiler enforcement to make sure that the determination is done purely on run-time type.
Whether they qualify or not is arguable. But in the world of C, describing say qsort or bsearch two Standard libC functions that handle arbitrary types using run-time dispatch via function pointer arguments as run-time polymorphic might aid quick understanding Still, there's doubtless hundreds of Computing Science textbooks out there with functional definitions of run-time polymorphism, and I'd bet dispatch using function pointers or other programmer-initialised metadata satisfied a good percentage of them.
So, it's pointless to be too insistent that there's a single unambiguous answer. Not polymorphic at all, as you have no branching based on type. A dynamic cast could consult the compiler-populated type meta-data in the run-time type of myA, and if you used that to only conditionally invoke the access to myB.
Polymorphism is achieved with virtual functions. But to have any effect, i. Now you can have pointers or references to A with different behaviour, depending on whether it's a B or C. Polymorphism is defined as one interface to control access to a general class of actions. There are two types of polymorphism one is compile time polymorphism and the other is run time polymorphism. Compile time polymorphism is functions and operators overloading. Runtime time polymorphism is done using inheritance and virtual functions.
Polymorphism means that functions assume different forms at different times. In case of compile time it is called function overloading.
For example, a program can consist of two functions where one can perform integer addition and other can perform addition of floating point numbers but the name of the functions can be same such as add. The function add is said to be overloaded. Two or more functions can have same name but their parameter list should be different either in terms of parameters or their data types.
The functions which differ only in their return types cannot be overloaded. The compiler will select the right function depending on the type of parameters passed. In cases of classes constructors could be overloaded as there can be both initialized and uninitialized objects. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Ask Question. Asked 8 years, 8 months ago. Active 8 years, 8 months ago. Viewed 17k times. My questions are :- 1 Is Runtime polymorphism achieved only with virtual functions?
Or is it even polymorphism? Aki Suihkonen In computer science, compile time refers to either the operations performed by a compiler the " compile - time operations" , programming language requirements that must be met by source code for it to be successfully compiled the " compile - time requirements" , or properties of the program that can be reasoned about.
Runtime and compile time are programming terms that refer to different stages of software program development. Compile - time is the instance where the code you entered is converted to executable while Run - time is the instance where the executable is running. Compile - time checking occurs during the compile time. Answer is, No, you can not override static method in Java, though you can declare method with same signature in sub class.
It won't be overridden in exact sense, instead that is called method hiding. As per Java coding convention, static methods should be accessed by class name rather than object. Templates are a compile-time construct and type deduction is a process when the compiler automatically figures out the template arguments. This is where static polymorphism comes in. There is no static polymorphism in your example because there is no polymorphism.
How is polymorphism achieved at compile time and runtime? Category: technology and computing programming languages. How do you achieve runtime polymorphism? How do you achieve polymorphism?
What are the different types of polymorphism? What is the advantage of runtime polymorphism? What is oops concept? How does polymorphism work? What do you mean by polymorphism? What is polymorphism and example?
Why method overriding is called runtime polymorphism? Why do we need Runtime Polymorphism in Java? Why we Cannot override static method? Function overriding is a part of runtime polymorphism. In function overriding, more than one method has the same name with different types of the parameter list.
It is achieved by using virtual functions and pointers. It provides slow execution as it is known at the run time. Thus, It is more flexible as all the things executed at the run time. In function overriding, we give the new definition to base class function in the derived class. At that time, we can say the base function has been overridden.
In function overriding, we have two definitions of the same function, one in the superclass and one in the derived class.
The decision about which function definition requires calling happens at runtime. A virtual function is declared by keyword virtual. The return type of virtual function may be int, float, void. A virtual function is a member function in the base class. We can redefine it in a derived class. It is part of run time polymorphism. The declaration of the virtual function must be in the base class by using the keyword virtual. A virtual function is not static.
The virtual function helps to tell the compiler to perform dynamic binding or late binding on the function. This is because we will have to create a pointer to the base class that refers to all the derived objects.
0コメント