My last post C++20: The Ranges Library, gave you the first impression of the ranges library. Today's post is about functional patterns: function composition and lazy evaluation. They become first-class citizens in C++20.

Thanks to the ranges library in C++20, working with the Standard Template Library (STL) will become much more comfortable and powerful. The algorithms of the ranges library are lazy, can work directly on the container and can easily be composed. To make it short: The comfort and the power of the ranges library are due to its functional ideas. Let me show you what that means.

Let me conclude my series to concepts with this meta-post. Are concepts an evolution or a revolution in C++? The answer to this question bothered me quite a time.

When you want to define a concrete type that works well in the C++ ecosystem, you should define a type that "behaves link an int". Formally, your concrete type should be a regular type. In this post, I define the concepts Regular and SemiRegular.

In my last post, I defined the concept Equal. Now, I go one step further and use the concept Equal to define the concept Ordering.

With this post, I start my last very exciting topic to concepts: define your concepts. Consequentially, I answer the questions I opened in previous posts.

C++20 has many predefined concepts. Consequentially, before you define your concept, you should know the existing ones. This post gives you an overview of the predefined concepts. To get the general idea of concepts, read my previous posts. 

The Template Introduction from the Concepts TS is a new way to use concepts. This syntactic variant is not included in the Concepts Draft and, therefore, in the C++20 standard. But, I don't know what the farther away future brings.

Today, my post is not about something new to concepts. It's about syntactic sugar. I write about abbreviated function templates. What? Abbreviated functions templates allow a sweet way to define templates.

Today, I have a simple answer to a challenging question: Where can I use my concept? Concepts can be used where auto is usable.