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72 lines (65 loc) · 2.03 KB
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//
// Created by william on 2021/6/13.
//
#include <iostream>
#include <random>
void f(int n1, int n2, int n3, const int& n4, int n5)
{
std::cout << n1 << ' ' << n2 << ' ' << n3 << ' ' << n4 << ' ' << n5 << '\n';
}
int g(int n1)
{
return n1;
}
struct Foo
{
void printSum(int n1, int n2)
{
std::cout << n1 + n2 << std::endl;
}
int data = 10;
};
void square(double x)
{
std::cout << x << "^2 == " << x * x << std::endl;
}
void product(double x, double y)
{
std::cout << x << "*" << y << " == " << x * y << std::endl;
}
void bindTest()
{
using namespace std::placeholders; // 对于_1, _2, _3...
// 演示参数重排序和按引用传递
int n = 7;
// （ _1 与 _2 来自 std::placeholders ，并表示将来会传递给 f1 的参数）
auto f1 = std::bind(f, _2, 42, _1, std::cref(n), n);
n = 10;
f1(1, 2, 1001);// 1 为 _1 所绑定， 2 为 _2 所绑定，不使用 1001
// 进行到 f(2, 42, 1, n, 7) 的调用
auto f2 = std::bind(f, _3, std::bind(g, 3), _3, 4, 5);
f2(10, 11, 12); // 进行到 f(12, g(12), 12, 4, 5); 的调用
// 常见使用情况：以分布绑定 RNG
std::default_random_engine e;
std::uniform_int_distribution<> d(0, 10);
std::function<int()> rnd = std::bind(d, e); // e 的一个副本存储于 rnd
for(int i =0; i <10; ++i)
std::cout << rnd() << ' ';
std::cout << '\n';
// 绑定指向成员函数指针
Foo foo;
auto f3 = std::bind(&Foo::printSum, &foo, 95, _1);
f3(5);
// 绑定指向数据成员指针
auto f4 = std::bind(&Foo::data, _1);
std::cout << f4(foo) << '\n';
// 智能指针亦能用于调用被引用对象的成员
std::cout << f4(std::make_shared<Foo>(foo)) << '\n'
<< f4(std::make_unique<Foo>(foo)) << '\n';
double arg[] = { 1, 2, 3 };
std::for_each(&arg[0], arg + 3, square);
std::cout << std::endl;
std::for_each(&arg[0], arg + 3, std::bind(product, _1, 2));
std::cout << std::endl;
std::for_each(&arg[0], arg + 3, std::bind(square, _1));
}