一元函数对象的使用例子

#include <iostream>#include <vector>#include <algorithm>using namespace std;template<class in, class out>class lessThan : public unary_function<in, out>{public:lessThan(in a):value(a){}out operator()(in t){return t < value;}private:in value;};int main(){int arr[] = {3, 2, 4, 1, 10, 11, 26, 18};vector<int> v(arr, arr + 8);int n = count_if(v.begin(), v.end(), lessThan<int, bool>(10));cout << n << endl;return 0;}