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.
Table of Contents
What is template in C++?
A 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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