cpp/named req/Callable

A type is a type for which the  and  operations (used by, e.g., std, std, and std) are applicable.

Requirements
The type satisfies  if

Given
 * , an object of type
 * , suitable list of argument types
 * , suitable return type

The following expressions must be valid:

Standard library
In addition, the following standard library facilities accept any type (not just ):