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Learn What Is Implicit Instantiation Of A Template In C++

Learn What Is Implicit Instantiation Of A Template In C++

One of the great features of modern C++ is templates. A template is a simple and very powerful statement in C++ that defines the operations of a class or function, and Template Instantiation is to create a new definition of a function, class, or member of a class from a template declaration with template argument types. In this article, we will explain the Implicit Instantiation of a Template in C++ with examples that can be used by a professional C++ Tool such as an IDE and compiler.

First of all, let’s try to explain what templates in C++ are.

What is template in C++?

template is a very powerful statement in C++ that simply defines the operations of a class, a function, an alias, or a variable and let the user may apply the same template on different types in those template operations. Templates are like macros in C++, considered in compilation except compiler checks types used before the template is expanded in its terms. In the compilation mechanism of a template in C++, the source code contains only a template for a function or class, but when it is compiled, the same template can be used on multiple data types.

For example, here is a function template that adds two a and b parameters in T type,

for example if a and b are int variables, this template can be used as below

and in the next lines same template can be used for the x and y float variables as below too,

Templates are powerful features of C++ that can be parameterized by one or more template parameters. These parameters can be a type template parameter, a non-type template parameter, or a template parameter.

What is template instantiation in C++?

Template Instantiation means to create a new definition of a function, class, or member of a class from a template declaration with template argument types. For example, a class template is not a type or an object, or any other entity, this does not generate a code from a source file that contains only a template definition. When instantiated, the code of a template appears.

Template instantiation can be done in two different ways:

  • Explicit instantiation
  • Implicit instantiation

In this article, we will explain what is explicit template instantiation,

What is the implicit instantiation of a template in C++?

The Implicit Instantiation of a template (or Implicit Template Instantiation) occurs when a template is used to declare a pointer variable or a variable with the provided arguments. In this situation, the compiler automatically generates the concrete class or function for the provided template arguments.

To do implicit instantiation, first, we should define a template, then the compiler instantiates a class template specialization and the template is declared implicitly.

Where is a simple implicit instantiation of template example in C++?

Here is a simple implicit class template instantiation example in C++.

Is there a full implicit instantiation of template example in C++?

Here is a example about class template and implicit template instantiation of this class template.

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About author

Dr. Yilmaz Yoru has 35+ years of coding with more than 30+ programming languages, mostly C++ on Windows, Android, Mac-OS, iOS, Linux, and some other operating systems. He graduated and received his MSc and PhD degrees from the Department of Mechanical Engineering of Eskisehir Osmangazi University. He is the founder and CEO of ESENJA LLC Company. His interests are Programming, Thermodynamics, Fluid Mechanics, Artificial Intelligence, 2D & 3D Designs, and high-end innovations.
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