cpp/named req/FunctionObject

A type is the type of an object that can be used on the left of the function call operator.

Requirements
The type satisfies  if


 * The type satisfies std, and

Given
 * , a value of type or
 * , suitable argument list, which may be empty

The following expressions must be valid:

Standard library

 * All pointers to functions satisfy this requirement.
 * All function objects defined in
 * Some return types of functions of