20 General utilities library [utilities]

20.15 Metaprogramming and type traits [meta]

20.15.8 Transformations between types [meta.trans]

20.15.8.1 General [meta.trans.general]

Subclause [meta.trans] contains templates that may be used to transform one type to another following some predefined rule.
Each of the templates in [meta.trans] shall be a Cpp17TransformationTrait ([meta.rqmts]).