function and bind of c++11

function, bind is a feature in TR1, has been integrated into the C++0X/C++11

How to use

1. Using TR1

Header file: <tr1/functional>
std::tr1::function
std::tr1::bind
std::tr1::placeholders::_N

2. Using C++0X/11

Header file: <functional>
std::function
std::bind
std::placeholders::_N

Role

Bind binds an existing function with a specific parameter and returns a new callable object function to be used

Example

A subtraction calculation function exists:

STD::TR1;

STD::TR1::p laceholders;

Calcsub (b) { B;} 

1. Bind all Parameters

function<int ()bind (&3);     

Bind calcsub to argument 10 and 3 using bind, resulting in a int(void) type of function (callable object)

So, call fun: fun() equivalent tocalcSub(10,3)

2. Binding several parameters

function<int (int)bind (&_1);     

That is, calcSub(10, _1) the callable object fun that bind produces.
Where the placeholder _1 represents: fun The 1th parameter will be the second parameter of the calcsub
So fun there is a parameter, type =calcsub the type of the second argument =int

Then: fun(3) equivalent tocalcSub(10,3)

Placeholders::_n represents the nth parameter of a generated callable object

function<int (int,int)bind (&_1);      

That is, calcSub(_2,_1) the callable object fun that bind produces.
and through the placeholder declaration:The 2nd parameter of fun will be the first argument (int) of Calcsub, and the 1th parameter of fun will be the second argument (int) of calcsub.

So fun there are two parameters, and the type is int
So:fun(10,3) = calcSub(3,10)

3. Bind can also bind class member functions

If there is a class:

MyClass {

Public

 Memfun (b) {...} 

};

If you want to bind member function Calcsub, you cannot forget that the first parameter of Calcsub is myclass* this

Ins

function<void (string,int)bind (&&_1);       

_2 declared: The 2nd parameter of fun as the second argument of memfun (int)
_1 declared: The 1th parameter of fun as the third parameter of Memfun (string)
So the fun parameter isstring,int

So:func("xxx", 10)等价于ins.calcSub(10, "xxx");

function and bind of c++11