bool func1(int a){    return a < 5;}struct func2: public unary_function
     
      {    bool operator()(int a)    {        return a < 5;    }};struct func3: public binary_function
      
       {    bool operator()(int a, int b)    {        return a == b;    }};int main(int argc, char* argv[]){    list
       
         int_list;    int_list.remove_if(func1);    int_list.remove_if(func2());    int_list.remove_if(bind1st(greater
        
         (), 5));    int_list.remove_if(bind2nd(less
         
          (), 5));    int_list.remove_if([](int& a){        return a < 5;    });}