Metaprogramming library (since C++11) - cppreference.com

C++ provides metaprogramming facilities, such as type traits, compile-time rational arithmetic, and compile-time integer sequences.

Type traits

The header <type_traits> provides compile-time template-based interfaces to query the properties of types.

Compile-time rational arithmetic

The header <ratio> provides types and functions for manipulating and storing compile-time ratios.

Compile-time integer sequences (since C++14)

Defined in header <utility>
integer_sequence (C++14)	implements compile-time sequence of integers (class template) [edit]

Compile-time reflection (since C++26)

The header <meta> provides facilities for static reflection and reflective metaprogramming.