Windows apps
Collapse the table of content
Expand the table of content
The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

function Class

Wrapper for a callable object.

template<class Fty>
   class function  // Fty of type Ret(T1, T2, ..., TN)
   : public unary_function<T1, Ret>       // when Fty is Ret(T1)
   : public binary_function<T1, T2, Ret>  // when Fty is Ret(T1, T2)
   typedef Ret result_type;

   function(const function& _Right);
   template<class Fty2>
      function(Fty2 fn);
   template<class Fty2, class Alloc>
       function (reference_wrapper<Fty2>, const Alloc& _Ax);
   template<class Fty2, class Alloc>
       void assign (Fty2, const Alloc& _Ax);
   template<class Fty2, class Alloc>
       assign (reference_wrapper<Fty2>, const Alloc& _Ax);
   function& operator=(nullptr_t);
   function& operator=(const function&);
   template<class Fty2>
      function& operator=(Fty2);
   template<class Fty2>
      function& operator=(reference_wrapper<Fty2>);
   void swap(function&);

   explicit operator bool() const;
   result_type operator()(T1, T2, ....., TN) const;

   const std::type_info& target_type() const;
   template<class Fty2>
      Fty2 *target();
   template<class Fty2>
      const Fty2 *target() const;
   template<class Fty2>
      void operator==(const Fty2&) const = delete;
   template<class Fty2>
      void operator!=(const Fty2&) const = delete;


The function type to wrap.


The allocator function.

The template class is a call wrapper whose call signature is Ret(T1, T2, ..., TN). You use it to enclose a variety of callable objects in a uniform wrapper.

Some member functions take an operand that names the desired target object. You can specify such an operand in several ways:

fn -- the callable object fn; after the call the function object holds a copy of fn

fnref -- the callable object named by fnref.get(); after the call the function object holds a reference to fnref.get()

right -- the callable object, if any, held by the function object right

npc -- a null pointer; after the call the function object is empty

In all cases, INVOKE(f, t1, t2, ..., tN), where f is the callable object and t1, t2, ..., tN are lvalues of types T1, T2, ..., TN respectively, must be well-formed and, if Ret is not void, convertible to Ret.

An empty function object does not hold a callable object or a reference to a callable object.

Header: <functional>

Namespace: std

Community Additions

© 2017 Microsoft