16 Library introduction [library]

16.3 Method of description [description]

16.3.3 Other conventions [conventions] Type descriptions [type.descriptions] General [type.descriptions.general]

The Requirements subclauses may describe names that are used to specify constraints on template arguments.142
These names are used in library Clauses to describe the types that may be supplied as arguments by a C++ program when instantiating template components from the library.
Certain types defined in [input.output] are used to describe implementation-defined types.
They are based on other types, but with added constraints.
Examples from [utility.requirements] include: Cpp17EqualityComparable, Cpp17LessThanComparable, Cpp17CopyConstructible.
Examples from [iterator.requirements] include: Cpp17InputIterator, Cpp17ForwardIterator.