C++仿函数(三)bind和lambda

头文件

#include

1. bind

示例一

void useBindDemo() {
	set myset;
	myset.insert(3);
	myset.insert(4);
	myset.insert(5);
	vector vec;
	transform(myset.begin(), myset.end(), back_inserter(vec), bind(multiplies(), placeholders::_1, 10));
	copy(vec.begin(), vec.end(), ostream_iterator(cout, " "));
}

示例二

//convert a regular function into functor
double Pow(double x, double y) {
	return pow(x, y);
}
void useBindDemo2() {
	set myset;
	myset.insert(3);
	myset.insert(4);
	myset.insert(5);
	deque d;
	//vector d;
	auto f = function(Pow);
	transform(myset.begin(), myset.end(), back_inserter(d), bind(f, placeholders::_1, 2));
        // d {9,16,25}
}

将某个容器中某个区间范围的数属于哪个范围

void useBindDemo3() {
	set myset;
	for (int t = 0; t < 20; t++) {
		myset.insert(t);
	}
	vector d;
	transform(myset.begin(), myset.end(), back_inserter(d),
		bind(logical_and(),
			bind(greater(), placeholders::_1, 2),
			bind(less(), placeholders::_1, 10)));
            //d {0 0 0 1 1 1 1 1 1 0 ......}
	copy(d.begin(), d.end(), ostream_iterator(cout, " "));
}

将某个范围的数拷贝到容器中

bool needCopy(int x) {
        return (x > 2 && x < 10);
}

void useBindDemo4() {
	set myset;
	for (int t = 0; t < 20; t++) {
		myset.insert(t);
	}
	vector d;
	transform(myset.begin(), myset.end(), back_inserter(d),needCopy);
}

这里我们发现，这拷贝进去的是 0 1 啊，不是我们想要的啊。那我们应该修改啊。自己尝试下吧。

2. lambda

void useLambda() {
	set myset;
	for (int t = 0; t < 20; t++) {
		myset.insert(t);
	}
	vector d;
	transform(myset.begin(), myset.end(), back_inserter(d),
		[](int x) {return ((x > 2) && (x < 10)); });

}