A function object is any object for which the function call operator is defined. C++ provides many built-in function objects as well as support for creation and manipulation of new function objects.
std::function
provides support for storing arbitrary function objects.
(C++11) | wraps callable object of any type with specified function call signature (class template) |
(C++11) | the exception thrown when invoking an empty std::function (class) |
(C++11) | creates a function object out of a pointer to a member (function template) |
std::invoke
can invoke any Callable object with given arguments.
(C++17) | invokes any Callable object with given arguments (function template) |
std::identity
is the identity function object: it returns its argument unchanged.
(C++20) | function object that returns its argument unchanged (class) |
std::bind_front
and std::bind
provide support for partial function application, i.e. binding arguments to functions to produce new functions.
(C++20) | binds a variable number of arguments, in order, to a function object (function template) |
(C++11) | binds one or more arguments to a function object (function template) |
(C++11) | indicates that an object is std::bind expression or can be used as one (class template) |
(C++11) | indicates that an object is a standard placeholder or can be used as one (class template) |
Defined in namespace std::placeholders |
|
---|---|
(C++11) | placeholders for the unbound arguments in a std::bind expression (constant) |
std::not_fn
creates a function object that negates the result of the callable object passed to it.
(C++17) | Creates a function object that returns the complement of the result of the function object it holds (function template) |
Searchers implementing several string searching algorithms are provided and can be used either directly or with std::search
.
(C++17) | standard C++ library search algorithm implementation (class template) |
(C++17) | Boyer-Moore search algorithm implementation (class template) |
(C++17) | Boyer-Moore-Horspool search algorithm implementation (class template) |
Reference wrappers allow reference arguments to be stored in copyable function objects:
(C++11) | CopyConstructible and CopyAssignable reference wrapper (class template) |
(C++11)(C++11) | creates a std::reference_wrapper with a type deduced from its argument (function template) |
(C++20)(C++20) | get the reference type wrapped in std::reference_wrapper (class template) |
C++ defines several function objects that represent common arithmetic and logical operations:
Arithmetic operations |
|
function object implementing x + y (class template) |
|
function object implementing x - y (class template) |
|
function object implementing x * y (class template) |
|
function object implementing x / y (class template) |
|
function object implementing x % y (class template) |
|
function object implementing -x (class template) |
|
Comparisons |
|
function object implementing x == y (class template) |
|
function object implementing x != y (class template) |
|
function object implementing x > y (class template) |
|
function object implementing x < y (class template) |
|
function object implementing x >= y (class template) |
|
function object implementing x <= y (class template) |
|
Logical operations |
|
function object implementing x && y (class template) |
|
function object implementing x || y (class template) |
|
function object implementing !x (class template) |
|
Bitwise operations |
|
function object implementing x & y (class template) |
|
function object implementing x | y (class template) |
|
function object implementing x ^ y (class template) |
|
(C++14) | function object implementing ~x (class template) |
C++20 defines a set of constrained comparison function objects. The equality operators (ranges::equal_to
and ranges::not_equal_to
) require the types of the arguments to model EqualityComparableWith
. The relational operators (ranges::less
, ranges::greater
, ranges::less_equal
, and ranges::greater_equal
) require the types of the arguments to model StrictTotallyOrderedWith
.
(C++20) | function object implementing x == y (class) |
(C++20) | function object implementing x != y (class) |
(C++20) | function object implementing x < y (class) |
(C++20) | function object implementing x > y (class) |
(C++20) | function object implementing x <= y (class) |
(C++20) | function object implementing x >= y (class) |
Several utilities that provided early functional support are deprecated in C++11 and removed in C++17 (old negators are deprecated in C++17 and removed in C++20):
Base |
|
(deprecated in C++11)(removed in C++17) | adaptor-compatible unary function base class (class template) |
(deprecated in C++11)(removed in C++17) | adaptor-compatible binary function base class (class template) |
Binders |
|
(deprecated in C++11)(removed in C++17) | function object holding a binary function and one of its arguments (class template) |
(deprecated in C++11)(removed in C++17) | binds one argument to a binary function (function template) |
Function adaptors |
|
(deprecated in C++11)(removed in C++17) | adaptor-compatible wrapper for a pointer to unary function (class template) |
(deprecated in C++11)(removed in C++17) | adaptor-compatible wrapper for a pointer to binary function (class template) |
(deprecated in C++11)(removed in C++17) | creates an adaptor-compatible function object wrapper from a pointer to function (function template) |
(deprecated in C++11)(removed in C++17) | wrapper for a pointer to nullary or unary member function, callable with a pointer to object (class template) |
(deprecated in C++11)(removed in C++17) | creates a wrapper from a pointer to member function, callable with a pointer to object (function template) |
(deprecated in C++11)(removed in C++17) | wrapper for a pointer to nullary or unary member function, callable with a reference to object (class template) |
(deprecated in C++11)(removed in C++17) | creates a wrapper from a pointer to member function, callable with a reference to object (function template) |
(deprecated in C++17)(removed in C++20) | wrapper function object returning the complement of the unary predicate it holds (class template) |
(deprecated in C++17)(removed in C++20) | wrapper function object returning the complement of the binary predicate it holds (class template) |
(deprecated in C++17)(removed in C++20) | constructs custom std::unary_negate object (function template) |
(deprecated in C++17)(removed in C++20) | constructs custom std::binary_negate object (function template) |
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