C++ concepts: FunctionObject

 

C++

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Technical Specifications

 

C++ concepts

Basic
DefaultConstructible CopyAssignable CopyConstructible	MoveAssignable (C++11) MoveConstructible (C++11) Destructible
Layout
TrivialType (C++11) TriviallyCopyable (C++11)	StandardLayoutType (C++11) PODType
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Iterator OutputIterator InputIterator	ForwardIterator BidirectionalIterator RandomAccessIterator ContiguousIterator (C++17)
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FormattedInputFunction UnformattedInputFunction	FormattedOutputFunction UnformattedOutputFunction
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CharTraits pos_type off_type Clock (C++11) BitmaskType	UnaryTypeTrait (C++11) BinaryTypeTrait (C++11) TransformationTrait (C++11) TrivialClock (C++11) LiteralType (C++11)

 

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

Requirements

The type T satisfies FunctionObject if

• The type T satisfies std::is_object, and

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

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.

Standard library

• All pointers to functions satisfy this requirement.