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C++ concepts: FunctionObject

From cppreference.com
< cpp‎ | concept
 
 
 

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

[edit] Requirements

The type T satisfies FunctionObject if

Given

  • f, a value of type T or const T
  • args, suitable argument list, which may be empty

The following expressions must be valid:

Expression Requirements
f(args) performs a function call

[edit] Notes

Functions and references to functions are not function object types, but can be used where function object types are expected due to function-to-pointer implicit conversion.

[edit] Standard library

In addition, the following standard library facilities require a FunctionObject which isn't Callable, Hash, or Predicate type.

std::unique_ptr