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.

cpp17.tar.gz

C++17

C++20

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++

# `constexpr if` (C++17) 

`constexpr if` enables us to compile source code
conditionally.

```c++
if constexpr (cond) statement1;
else statement2;
```
- The expression `cond` has to be a constant expression. 
- The unused code has to be valid.
- Thanks to `constexpr if`, functions can have different return types.


The following code snippet shows a function, which returns an `int` or a `double`. 

```c++
template <typename T>
auto getAnswer(T t){
  static_assert(std::is_arithmetic_v<T>); // arithmetic
  if constexpr (std::is_integral_v<T>)    // integral
    return 42;
  else                                    
    return 42.0;        // floating point
}
```



`constexpr if` is a replacement for tag dispatch and [SFINAE](https://en.wikipedia.org/wiki/Substitution_failure_is_not_an_error). SFINAE stands for **S**ubstitution **F**ailure **I**s **N**ot **A**n **E**rror.

To study further about tag dispatching, click [here](https://www.educative.io/courses/generic-templates-in-cpp/idioms-and-patterns-tag-dispatching).

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In the next lesson, we'll look at an example of `constexpr if`.

Introduction

Basics

Details

Techniques

Design

Future

Conclusion

constexpr if

`constexpr if` (C++17)

constexpr if

constexpr if (C++17)

`constexpr if` (C++17)