16 Library introduction [library]

16.3 Method of description [description]

16.3.3 Other conventions [conventions] Type descriptions [type.descriptions] Exposition-only types [expos.only.types]

Several types defined in [support] through [thread] and [depr] are defined for the purpose of exposition.
The declaration of such a type is followed by a comment ending in exposition only.
[Example 1: namespace std { extern "C" using some-handler = int(int, void*, double); // exposition only }
The type placeholder some-handler can now be used to specify a function that takes a callback parameter with C language linkage.
— end example]