There are more reasons to prefer ranges library above the classical Standard Template Library. The ranges iterators support unified lookup rules and provide additional safety guarantees.

The ranges library in C++20 supports sentinels. Sentinels stand for the end of a range and can be regarded as generalized end iterators.

The algorithms of the ranges library are lazy, can work directly on the container, and can easily be composed. But they have more to offer: projections. A projection is a mapping of a set into a subset. Let me show you in this post what that means:

Working with the Standard Template Library (STL) is much more comfortable and powerful thanks to the ranges library. The algorithms of the ranges library are lazy, can work directly on the container, and can quickly be composed. But there is more to it:

Concepts are a powerful and elegant tool to check at compile time if a type fulfills. Thanks to static_assert, you can use concepts as a standalone feature: static_assert(Concept<T>).

static_assert allows you to check at compile time if a type T fulfills the Concept: static_assert(Concept<T>).

In my last post "Defining Concepts with Requires Expressions", I exemplified how you can use requires expressions to define concepts. Requires expressions can also be used as a standalone feature when a compile-time predicate is required.

In my last post, "Define Concepts", I defined the concepts Integral, SignedIntegral, and UnsigendIntegral using logical combinations of existing concepts and compile-time predicates. Today, I use Requires Expressions to define concepts.

There are two ways to define a concept: You can combine existing concepts and compile-time predicates, or you can apply a requires expression in four different ways.

In the last weeks, I learned something new about modules in C++20: private modules fragments and header units. Consequently, I make a short detour in this post and present these new features.