#include <iostream>#include <vector>#include <string>#include <iterator>#include <algorithm>#include <functional>  /**  * std::bind1st  std::bind2nd 就是将一个二元函数的一个参数设置为定值，这样二元函数就转换为了一元函数* 因为有些算法的参数要求必须是一元函数，但是我们又想用二元函数，那么就可以使用这两个函数*//***@brief std::less 仿函数的内部实现    template <class T> struct less : binary_function <T,T,bool> {        bool operator() (const T& x, const T& y) const {return x<y;}    };*/ struct person{    int age;    std::string name;}; struct person_filter_func: public std::binary_function<person,std::string,bool>{    bool operator()(const person& p,const std::string& key) const{        return (p.name.find(key) != std::string::npos);     }}; void disp(int val){    std::cout<<val<<std::endl; }void disp_v(const person& p){    std::cout<<p.age<<","<<p.name<<std::endl; } int main(){    //使用 std::less 仿函数    int arr[] = {1,2,3,4,5,6,7,8,9};    std::vector<int> vec;    std::copy_if(std::begin(arr),std::end(arr),std::back_inserter(vec),std::bind1st(std::less<int>(),6)); //将6 绑定为第一个参数，即 6 < value    std::for_each(vec.begin(),vec.end(),disp);  // 7 8 9     vec.clear();    std::copy_if(std::begin(arr),std::end(arr),std::back_inserter(vec),std::bind2nd(std::less<int>(),6)); //将6 绑定为第二个参数，即 value < 6    std::for_each(vec.begin(),vec.end(),disp); //1 2 3 4 5      //使用自定义的仿函数    std::vector<person> vecP;    person p1 = {1,"jack"}; vecP.push_back(p1);    person p2 = {2,"rose"}; vecP.push_back(p2);    person p3 = {3,"jane"}; vecP.push_back(p3);     std::vector<person> vecRet;    std::copy_if(vecP.begin(),vecP.end(),std::back_inserter(vecRet),std::bind2nd(person_filter_func(),"ja"));  //将包含关键字"ja"的person，复制到vecRet容器中    std::for_each(vecRet.begin(),vecRet.end(),disp_v);//1, jack  3, jane}

template <class InputIterator, class OutputIterator, class UnaryPredicate>  OutputIterator copy_if (InputIterator first, InputIterator last,                          OutputIterator result, UnaryPredicate pred){  while (first!=last) {    if (pred(*first)) {      *result = *first;      ++result;    }    ++first;  }  return result;}

template <class Operation, class T>  binder1st<Operation> bind1st (const Operation& op, const T& x){  return binder1st<Operation>(op, typename Operation::first_argument_type(x));}

template <class Operation> class binder1st  : public unary_function <typename Operation::second_argument_type,                           typename Operation::result_type>{protected:  Operation op;  typename Operation::first_argument_type value;public:  binder1st ( const Operation& x,              const typename Operation::first_argument_type& y) : op (x), value(y) {}  typename Operation::result_type    operator() (const typename Operation::second_argument_type& x) const    { return op(value,x); }};

template <class ForwardIterator, class UnaryPredicate>  ForwardIterator remove_if (ForwardIterator first, ForwardIterator last,                             UnaryPredicate pred){  ForwardIterator result = first;  while (first!=last) {    if (!pred(*first)) {      *result = std::move(*first);      ++result;    }    ++first;  }  return result;}