Re: What does this class do?

From:

Fei Liu <feiliu@aepnetworks.com>

Newsgroups:

comp.lang.c++

Date:

Tue, 24 Apr 2007 16:38:43 -0400

Message-ID:

<f0lth9$mvn$1@aioe.org>

desktop wrote:

I found this class at:

http://www.icce.rug.nl/documents/cplusplus/cplusplus17.html#FINDEND

  class Twice
    {
        public:
            bool operator()(size_t first, size_t second) const
            {
                return first == (second << 1);
            }
    };

it is used as the last argument to find_end() but I don't understand
what it does and why it is needed.

I have tried calling it with various integers but it always outputs 0:

    Twice t = Twice();
    bool t_bool = t.operator ()(4,8);
    std::cout << t_bool << std::endl;

Try this instead:

#include <iostream>
using namespace std;

class Twice
     {
         public:
             bool operator()(size_t first, size_t second) const
             {
                 return first == (second << 1);
             }
     };

int main(){
     Twice t = Twice();
     bool t_bool = t.operator ()(8, 4);
     std::cout << t_bool << std::endl;
}

I suppose you need to look up how '<<' works.