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Standard library header <functional>

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This header is part of the function objects library and provides the standard hash function.

Contents

[edit] Namespaces

placeholders Defines placeholders for the unbound arguments in a std::bind expression
Constants
Defined in namespace std::placeholders
placeholders for the unbound arguments in a std::bind expression
(constant) [edit]

[edit] Classes

(C++11)
wraps callable object of any type with specified function call signature
(class template) [edit]
(C++11)
creates a function object out of a pointer to a member
(function template) [edit]
the exception thrown when invoking an empty std::function
(class) [edit]
indicates that an object is std::bind expression or can be used as one
(class template) [edit]
indicates that an object is a standard placeholder or can be used as one
(class template) [edit]
CopyConstructible and CopyAssignable reference wrapper
(class template) [edit]
Hashing
(C++11)
hash function object
(class template) [edit]
template<> struct hash<bool>;

template<> struct hash<char>;
template<> struct hash<signed char>;
template<> struct hash<unsigned char>;
template<> struct hash<char16_t>;
template<> struct hash<char32_t>;
template<> struct hash<wchar_t>;
template<> struct hash<short>;
template<> struct hash<unsigned short>;
template<> struct hash<int>;
template<> struct hash<unsigned int>;
template<> struct hash<long>;
template<> struct hash<long long>;
template<> struct hash<unsigned long>;
template<> struct hash<unsigned long long>;
template<> struct hash<float>;
template<> struct hash<double>;
template<> struct hash<long double>;
template< class T > struct hash<T*>;

std::hash specializations for built-in types
(class template specialization)


[edit] Functions

(C++11)
binds one or more arguments to a function object
(function template) [edit]
(C++11)(C++11)
creates a std::reference_wrapper with a type deduced from its argument
(function template) [edit]


[edit] Function Objects

Arithmetic operations
function object implementing x + y
(class template) [edit]
function object implementing x - y
(class template) [edit]
function object implementing x * y
(class template) [edit]
function object implementing x / y
(class template) [edit]
function object implementing x % y
(class template) [edit]
function object implementing -x
(class template) [edit]
Comparisons
function object implementing x == y
(class template) [edit]
function object implementing x != y
(class template) [edit]
function object implementing x > y
(class template) [edit]
function object implementing x < y
(class template) [edit]
function object implementing x >= y
(class template) [edit]
function object implementing x <= y
(class template) [edit]
Logical operations
function object implementing x && y
(class template) [edit]
function object implementing x || y
(class template) [edit]
function object implementing !x
(class template) [edit]
Bitwise operations
function object implementing x & y
(class template) [edit]
function object implementing x | y
(class template) [edit]
function object implementing x ^ y
(class template) [edit]
Negators
wrapper function object returning the complement of the unary predicate it holds
(class template) [edit]
wrapper function object returning the complement of the binary predicate it holds
(class template) [edit]
constructs custom std::unary_negate object
(function template) [edit]
constructs custom std::binary_negate object
(function template) [edit]

[edit] Deprecated in C++11

Base
(until C++17)
adaptor-compatible unary function base class
(class template) [edit]
(until C++17)
adaptor-compatible binary function base class
(class template) [edit]
Binders
(until C++17)(until C++17)
function object holding a binary function and one of its arguments
(class template) [edit]
(until C++17)(until C++17)
binds one argument to a binary function
(function template) [edit]
Function adaptors
adaptor-compatible wrapper for a pointer to unary function
(class template) [edit]
adaptor-compatible wrapper for a pointer to binary function
(class template) [edit]
(until C++17)
creates an adaptor-compatible function object wrapper from a pointer to function
(function template) [edit]
(until C++17)(until C++17)(until C++17)(until C++17)
wrapper for a pointer to nullary or unary member function, callable with a pointer to object
(class template) [edit]
(until C++17)
creates a wrapper from a pointer to member function, callable with a pointer to object
(function template) [edit]
(until C++17)(until C++17)(until C++17)(until C++17)
wapper for a pointer to nullary or unary member function, callable with a reference to object
(class template) [edit]
(until C++17)
creates a wrapper from a pointer to member function, callable with a reference to object
(function template) [edit]

[edit] Synopsis

namespace std {
 
    // base (deprecated):
    template <class Arg, class Result> struct unary_function;
    template <class Arg1, class Arg2, class Result> struct binary_function;
 
    // reference_wrapper:
    template <class T> class reference_wrapper;
    template <class T> reference_wrapper<T> ref(T&) noexcept;
    template <class T> reference_wrapper<const T> cref(const T&) noexcept;
    template <class T> void ref(const T&&) = delete;
    template <class T> void cref(const T&&) = delete;
    template <class T> reference_wrapper<T> ref(reference_wrapper<T>) noexcept;
    template <class T> reference_wrapper<const T> cref(reference_wrapper<T>) noexcept;
 
    // arithmetic operations:
    template <class T> struct plus;
    template <class T> struct minus;
    template <class T> struct multiplies;
    template <class T> struct divides;
    template <class T> struct modulus;
    template <class T> struct negate;
 
    // comparisons:
    template <class T> struct equal_to;
    template <class T> struct not_equal_to;
    template <class T> struct greater;
    template <class T> struct less;
    template <class T> struct greater_equal;
    template <class T> struct less_equal;
 
    // logical operations:
    template <class T> struct logical_and;
    template <class T> struct logical_or;
    template <class T> struct logical_not;
 
    // bitwise operations:
    template <class T> struct bit_and;
    template <class T> struct bit_or;
    template <class T> struct bit_xor;
 
    // negators:
    template <class Predicate> class unary_negate;
    template <class Predicate>
        unary_negate<Predicate> 
        not1(const Predicate&);
    template <class Predicate>  class binary_negate;
    template <class Predicate>
        binary_negate<Predicate>
        not2(const Predicate&);
 
    // bind:
    template<class T> struct is_bind_expression;
    template<class T> struct is_placeholder;
    template<class  F, class... BoundArgs>
        /*unspecified*/ bind(F&&, BoundArgs&&...);
    template<class  R, class F, class... BoundArgs>
        /*unspecified*/ bind(F&&, BoundArgs&&...);
 
    namespace placeholders {
        // M is the implementation-defined number of placeholders
        extern /*unspecified*/ _1;
        extern /*unspecified*/ _2;
        .
        .
        .
        extern /*unspecified*/ _M;
    }
 
    // binders (deprecated):
    template <class Fn> class binder1st;
    template <class Fn, class T>
        binder1st<Fn> bind1st(const Fn&, const T&);
    template <class Fn> class binder2nd;
    template <class Fn, class T>
        binder2nd<Fn> bind2nd(const Fn&, const T&);
 
    // adaptors (deprecated):
    template <class Arg, class Result> class pointer_to_unary_function;
    template <class Arg, class Result>
        pointer_to_unary_function<Arg,Result> ptr_fun(Result (*)(Arg));
    template <class Arg1, class Arg2, class Result>
        class pointer_to_binary_function;
    template <class Arg1, class Arg2, class Result>
        pointer_to_binary_function<Arg1,Arg2,Result>
        ptr_fun(Result (*)(Arg1,Arg2));
 
    // adaptors (deprecated):
    template<class S, class T> class mem_fun_t;
    template<class S, class T, class A> class mem_fun1_t;
    template<class S, class T>
        mem_fun_t<S,T> mem_fun(S (T::*f)());
    template<class S, class T, class A>
        mem_fun1_t<S,T,A> mem_fun(S (T::*f)(A));
    template<class S, class T> class mem_fun_ref_t;
    template<class S, class T, class A> class mem_fun1_ref_t;
    template<class S, class T>
        mem_fun_ref_t<S,T> mem_fun_ref(S (T::*f)());
    template<class S, class T, class A>
        mem_fun1_ref_t<S,T,A> mem_fun_ref(S (T::*f)(A));
    template <class S, class T> class const_mem_fun_t;
    template <class S, class T, class A> class const_mem_fun1_t;
    template <class S, class T>
        const_mem_fun_t<S,T> mem_fun(S (T::*f)() const);
    template <class S, class T, class A>
        const_mem_fun1_t<S,T,A> mem_fun(S (T::*f)(A) const);
    template <class S, class T> class const_mem_fun_ref_t;
    template <class S, class T, class A> class const_mem_fun1_ref_t;
    template <class S, class T>
        const_mem_fun_ref_t<S,T> mem_fun_ref(S (T::*f)() const);
    template <class S, class T, class A>
        const_mem_fun1_ref_t<S,T,A> mem_fun_ref(S (T::*f)(A) const);
 
    // member function adaptors:
    template<class R, class T> /*unspecified*/ mem_fn(R T::*);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...));
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) const);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) volatile);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) const volatile);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) &);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) const &);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) volatile &);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) const volatile &);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) &&);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) const &&);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) volatile &&);
    template<class R, class T, class... Args>
        /*unspecified*/ mem_fn(R (T::*)(Args...) const volatile &&);
 
    // polymorphic function wrappers:
    class bad_function_call;
    template<class> class function; // undefined
    template<class R, class... ArgTypes> class function<R(ArgTypes...)>;
    template<class R, class... ArgTypes>
        void swap(function<R(ArgTypes...)>&, function<R(ArgTypes...)>&);
    template<class R, class... ArgTypes>
        bool operator==(const function<R(ArgTypes...)>&, nullptr_t);
    template<class R, class... ArgTypes>
        bool operator==(nullptr_t, const function<R(ArgTypes...)>&);
    template<class R, class... ArgTypes>
        bool operator!=(const function<R(ArgTypes...)>&, nullptr_t);
    template<class R, class... ArgTypes>
        bool operator!=(nullptr_t, const function<R(ArgTypes...)>&);
 
    // hash function base template:
    template <class T> struct hash;
 
    // Hash function specializations
    template <> struct hash<bool>;
    template <> struct hash<char>;
    template <> struct hash<signed char>;
    template <> struct hash<unsigned char>;
    template <> struct hash<char16_t>;
    template <> struct hash<char32_t>;
    template <> struct hash<wchar_t>;
    template <> struct hash<short>;
    template <> struct hash<unsigned short>;
    template <> struct hash<int>;
    template <> struct hash<unsigned int>;
    template <> struct hash<long>;
    template <> struct hash<long long>;
    template <> struct hash<unsigned long>;
    template <> struct hash<unsigned long long>;
    template <> struct hash<float>;
    template <> struct hash<double>;
    template <> struct hash<long double>;
    template<class T> struct hash<T*>;
 
}


[edit] Class std::reference_wrapper

template <class T> class reference_wrapper {
public :
    // types
    typedef T type;
    typedef /*Return type of T*/     result_type;          // not always defined
    typedef /*Single argument of T*/ argument_type;        // not always defined
    typedef /*1st argument of T*/    first_argument_type;  // not always defined
    typedef /*2nd argument of T*/    second_argument_type; // not always defined
 
    // construct/copy/destroy
    reference_wrapper(T&) noexcept;
    reference_wrapper(T&&) = delete;
 
    // do not bind to temporary objects
    reference_wrapper(const reference_wrapper<T>& x) noexcept;
 
    // assignment
    reference_wrapper& operator=(const reference_wrapper<T>& x) noexcept;
 
    // access
    operator T& () const noexcept;
    T& get() const noexcept;
 
    // invocation
    template <class... ArgTypes>
        typename result_of<T&(ArgTypes&&...)>::type
        operator() (ArgTypes&&...) const;
 
};

[edit] Class std::is_bind_expression

template<class T> struct is_bind_expression
    : integral_constant<bool, /*true


[edit] Class std::bad_function_call

class bad_function_call : public std::exception {
public:
    // constructor:
    bad_function_call() noexcept;
};

[edit] Class std::function

template<class> class function; // undefined
 
template<class R, class... ArgTypes>
class function<R(ArgTypes...)> {
public:
    typedef R result_type;      
    typedef T1 argument_type;       //  iff sizeof...(ArgTypes) == 1 and
                                    //  the type in ArgTypes is T1
    typedef T1 first_argument_type; //  iff sizeof...(ArgTypes) == 2 and
                                    //  ArgTypes contains T1 and T2
    typedef T2 second_argument_type;//  iff sizeof...(ArgTypes) == 2 and
                                    //  ArgTypes contains T1 and T2
 
    // construct/copy/destroy:
    function() noexcept;
    function(nullptr_t) noexcept;
    function(const function&);
    function(function&&);
 
    template<class F> function(F);
    template<class A> function(allocator_arg_t, const A&) noexcept;
    template<class A> function(allocator_arg_t, const A&, nullptr_t) noexcept;
    template<class A> function(allocator_arg_t, const A&, const function&);
    template<class A> function(allocator_arg_t, const A&, function&&);
    template<class F, class A> function(allocator_arg_t, const A&, F);
 
    function& operator=(const function&);
    function& operator=(function&&);
    function& operator=(nullptr_t);
    template<class F> function& operator=(F&&);
    template<class F> function& operator=(reference_wrapper<F>) noexcept;
 
    ~function();
 
    // function modifiers:
    void swap(function&) noexcept;
    template<class F, class A> void assign(F&&, const A&);
 
    // function capacity:
    explicit operator bool() const noexcept;
 
    // function invocation:
    R operator()(ArgTypes...) const;
 
    // function target access:
    const std::type_info& target_type() const noexcept;
    template <typename T>       T* target() noexcept;
    template <typename T> const T* target() const noexcept;
 
};


[edit] See Also

<string> Specializes std::hash for std::string, std::u16string, std::u32string, std::wstring
<system_error> Specializes std::hash for std::error_code
<bitset> Specializes std::hash for std::bitset
<memory> Specializes std::hash for std::unique_ptr, std::shared_ptr
<typeindex> Specializes std::hash for std::type_index
<vector> Specializes std::hash for std::vector<bool>
<thread> Specializes std::hash for std::thread::id