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is_polymorphic template in C++

C++ has become one of the most effective coding languages in existence for programmers. The is_polymorphism template is just one of these features, which is utilized though seldom and comes in handy when needed. This blog post will investigate the syntax, implementation, and merits of the is_polymorphic template in C++, complete with sample code snippets and outcomes.

Polymorphism in C++

Object-oriented programming features polymorphism, which means that objects from various types may be used as if they are the same type of objects. Usually, it is done using virtual functions and an object pointer or reference type to the base class type. Therefore, polymorphism helps programs to be written with less specific features and, are easier to change or extend without breaking existing programs.

Introducing is_polymorphic

Is_polymorphic is one of the many algorithms provided under type_traits header in C++ that offers compile time inspection and type information. Is_polymorphic is applied to check whether any particular type is polymorphic (in the sense of having at least one virtual function).


The syntax of is_polymorphic is relatively straightforward:

Here, the class is of type MyClass and we would like to find polymorphism. If the type is polymorphic, the value member is_polymorphic will be true; otherwise, it will be false.

Example Code:

For more clarity, let us have a look at a practical case study of using is_polymorphic. Consider the following code snippet:


Circle is polymorphic: 1
Square is polymorphic: 1


In this example, the pure virtual function, draw(), is included in a base class known as Shape. It means that the Shape class is abstract, and a concrete class derived from it should have draw() method implemented. Derived concretely from the abstract class is a class called "Shape" with two sub-classes named "Circle" and "Square", each giving its own specific implementation of the function "draw()".

After that, moving to the main() function, and then the program uses the std::is_polymorphic template to validate that Circle and Square classes are polymorphic. Boolean variables such as isPolyCircle and isPolySquare hold the results.

The program will show whether each class is polymorphic or not. If this class contains at least one virtual function, the polymorphism requirement is met. It will be false otherwise.

This output means that both Circle and Square can be classified as polymorphic because they inherit from the abstract type called Shape, which is equipped with the virtual member function. The program performs these checks at compile-time using the is_polymorphic template, which can help choose types in C++.

Use Cases and Benefits:

In many instances, it is important to know at compile-time if certain types are polymorphic or not. Here are some use cases where is_polymorphic can be particularly useful:

Runtime Type Information (RTTI) Avoidance:

If type checks are involved, it is recommended to use is_polymorphic rather than RTTI. Run-time checks are often less effective compared to compile-time checks.

Template Specialization:

Using template specialization, you can write customized code for both polymorphic and non-polymorphic types. In essence, this helps in more effective and customized processes for every case.

Code Generation:

You either generate code dynamically depending on whether a type is polymorphic or statically based on information obtained at compile-time. For instance, you could instantiate dynamic instances for polymorphic types but have no problem handling static non-polymorphic types.

Library Design:

In this regard, is_polymorphic promotes the development of type-safe interfaces that cater for a variety of different types when building generic libraries.

Next Topicis_trivial in C++

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