#include <functional>
#include <numeric>
#include <iostream>
// help function
int f(int n,char c,double d)
{
std::cout << n << std::endl;
std::cout << c << std::endl;
std::cout << d << std::endl;
return 1;
}
int g(int) { return 2; }
// g() is overloaded
double g(double){ return 3;}
// take something you can call using ()
struct int_div {
float operator()(int x, int y) const { return ((float)x)/y; };
};
struct x {
int foo(int) { return 4; };
};
void bind_test()
{
// std::placeholders,it looks like closure at javascript.
// the std::placeholders namespace contains the placeholder objects [_1, . . . _n] where n is an implementation defined maximum number.
// when used as an argument in a std::bind expression, the placeholder objects are stored in the generated function object,
// and when that function object is invoked with unbound arguments, each placeholder _n is replaced by the corresponding nth unbound argument.
// deduce return type
auto ff = std::bind(f,std::placeholders::_1,'c',1.2);
// f(7,'c',1.2);
int x = ff(7);
auto fff = std::bind(f,std::placeholders::_1,std::placeholders::_2,1.2);
// f(8,'d',1.2);
x = fff(8,'d');
auto ffff = std::bind(f,9,'e',1.2);
// f(9,'e',1.2);
x = ffff();
// reverse argument order
auto frev = std::bind(f,std::placeholders::_3,std::placeholders::_2,std::placeholders::_1);
// f(7,'c',1.2);
x = frev(1.2,'c',7);
// error: which g()?
//auto g1 = std::bind(g,std::placeholders::_1);
// ok (but ugly)
auto g2 = std::bind((double(*)(double))g,std::placeholders::_1);
// explicit return type
auto f2 = std::bind<int>(f,7,'c',std::placeholders::_1);
// f(7,'c',1.2);
x = f2(1.2);
}
void function_test()
{
// function is a type that can hold a value of just about anything you can invoke using the (...) syntax.
// in particular, the result of bind can be assigned to a function. function is very simple to use. for example:
// make a function object
std::function<float (int x, int y)> f;
// assign
f = int_div();
// call through the function object
std::cout << f(5, 3) << std::endl;
// passes beautifully
int init = 100;
int numbers[] = {10,20,30};
std::cout << std::accumulate(numbers,numbers 2,init,f) << std::endl;
// member functions can be treated as free functions with an extra argument(this pointer)
std::function<int (x*, int)> f1;
// pointer to member
// something
// not support by vs2012?
// gcc version 4.8.2 is
f1 = &x::foo;
x x;
// call x::foo() for x with 5
int v = f1(&x, 5);
// first argument for f is &x
std::function<int (int)> ff1 = std::bind(f1,&x,std::placeholders::_1);
// call x.foo(5)
v=ff1(5);
}
int main()
{
bind_test();
function_test();
return 0;
}

注意：linux下，gcc version4.82如果不能识别auto,编译时加上-std=c 11,比如： g -g -o function_bind_test function_bind_test.cc

reference from:

c 11 test code for preview.-凯发app官方网站

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