[Boost-users] Trying to understand the details of boost function

From: Khandelwal, Amit (amit.khandelwal_at_[hidden])
Date: 2008-06-13 10:56:42

I am trying to understand the details of boost function. Below is the
sample code that I am using. I was expecting the copy constructor to be
invoked once. However, I see that it is called four times. I am trying
to understand why does boost function need to have four copies of my
objects. I am using boost version 1_33_1. 

Any thoughts/comments..

#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include "boost/function.hpp"
#include <map>

using namespace std;

class F
{
    public:
    F() {
        cout << "Cons" << endl;
    }
    F(const F&) {
        cout << "Copy const" << endl;
    }
    F& operator=(const F&) {
        cout << "operator = " << endl;
        return *this;
    }
    int operator()(int a, int b) { cout <<" Sub" << endl; return a - b;
}
};

int main() {
     FUNC f = F();
}

Output:

Cons
Copy const
Copy const
Copy const
Copy const
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

This message is intended only for the personal and confidential use of the designated recipient(s) named above.  If you are not the intended recipient of this message you are hereby notified that any review, dissemination, distribution or copying of this message is strictly prohibited.  This communication is for information purposes only and should not be regarded as an offer to sell or as a solicitation of an offer to buy any financial product, an official confirmation of any transaction, or as an official statement of Lehman Brothers.  Email transmission cannot be guaranteed to be secure or error-free.  Therefore, we do not represent that this information is complete or accurate and it should not be relied upon as such.  All information is subject to change without notice.

--------
IRS Circular 230 Disclosure:
Please be advised that any discussion of U.S. tax matters contained within this communication (including any attachments) is not intended or written to be used and cannot be used for the purpose of (i) avoiding U.S. tax related penalties or (ii) promoting, marketing or recommending to another party any transaction or matter addressed herein.