Gain insights into C++20 Concepts to enhance type safety. Delve into creating compiler-checked criteria for templates and improving error clarity for seamless generic code development.

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c++20

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This course will walk you through the newest version of C++ 20, C++ Concepts.

You will go through one of the most significant new features in C++20, which is Concepts. Concepts allow you to create compiler-checked criteria for template parameters, revolutionizing the way you think about and develop generic code. You can use them to provide both syntactic and semantic requirements. They also allow you to explicitly express your goal in the type system. If something goes wrong, you'll get a clear error message from the compiler.

While useful, Concepts can be difficult to apply and even confusing sometimes. This course provides you with the knowledge you need to overcome these obstacles and move on to more complex topics.

Let's get started.

C++ Concepts: Improve Type Safety with C++ 20

# How to write trailing `requires` clause

We can also use the trailing `requires` clause that comes after the function parameter list (and any qualifiers, like `const` or `override`) and before the function implementation.

```c++
template <typename T>
auto add(T a, T b) requires Number<T> {
  return a+b;
}
```

This gives the same result as the `requires` clause; we just wrote it with different semantics. It still means that we can’t add two numbers of different types. We also need to modify the template definition as we did before:

```c++
template <typename T, typename U>
auto add(T a, U b) requires Number<T> && Number<U> {
  return a+b;
}
```

# More constraints

Still, we face the drawback of scalability. Each new function parameter, potentially of a different type, needs its own template parameter.

Just as for the `requires` clause, we can express more complex constraints in the trailing `requires` clause.

```c++
template <typename T>
auto add(T a, T b) requires std::integral<T> || std::floating_point<T> {
  return a+b;
}
```

Get an overview of the trailing <requires> clause. 

The Trailing <requires> Clause

Get an overview of the trailing <requires> clause.

Introduction

The Concept Behind C++ Concepts

Four Ways to use Concepts in Functions

C++ Concepts with Classes

Concepts Shipped with the C++ Standard Library

How to Write Your Own C++ Concepts

How to Use C++ Concepts in Real Life

Summary

The Trailing <requires> Clause

How to write trailing `requires` clause

The Trailing <requires> Clause

How to write trailing requires clause

How to write trailing `requires` clause