Explore the power of C++ templates, from function and class basics to advanced features like instantiation and concepts, enhancing code flexibility, reusability, and abstraction without performance loss.

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Templates are one of the many powerful features of Modern C++ programming. And with each new C++ standard, they become more important. 

Templates provide an efficient way to make your code more flexible and reusable, this way you can avoid repeating code that would otherwise be identical except for different types. Templates also give you the ability to provide abstraction without a performance penalty.

However, templates can be difficult to apply, can be counterintuitive, and have tricky error messages.

This course gives you the necessary information to overcome these hurdles and dive into the advanced topics. You’ll visit the basics such as function and class templates, and then explore the details to templates such as instantiation and fold expressions. Our journey also includes techniques based on templates, the design, and future directions of templates such as concepts. Based on this exhaustive tour of templates, a basic understanding of C++ is sufficient to master this course.

Let’s get started!

Generic Programming Templates in C++

# Variadic Templates
A variadic template is a template that can has an arbitrary number of parameters.
```c++
template <typename ... Args>
void variadicTemplate(Args ... args){ . . . . }
```
## Parameter Pack

A template parameter pack is a template parameter that accepts zero or more template arguments (non-types, types, or templates). A function parameter pack is a function parameter that accepts zero or more function arguments.


* By using the ellipse (...), `Args-` or `args` becomes a parameter pack.
* `Args` is a template parameter pack; `args` is a function parameter pack.
* Parameter packs can only be packed and unpacked.
* If the ellipsis is left from `Args`, the parameter pack will be packed and if the ellipse is right from `Args`, the parameter pack will be unpacked.

>The compiler can automatically deduce the template arguments in case of a function template.

For example, the following classes/functions in STL extensively use variadic templates.
Variadic Templates are often used in the Standard Template Library:
* `sizeof`-Operator, `std::tuple`, `std::thread`, `std::make_unique`, `std::lock`


 The usage of parameter packs obeys a typical pattern for class templates.

* Perform an operation on the first element of the parameter pack and recursively invoke the operation on the remaining elements.
* The recursion ends after a finite number of steps. 
* The boundary condition is typically a fully specialized template.



Let's learn about variadic templates in detail in this lesson.

Introduction

Basics

Details

Techniques

Design

Future

Conclusion

Variadic Templates

Variadic Templates