----- Original Message -----

From: Oliver Seiler

Newsgroups: gmane.comp.lib.boost.user

To: boost-users@lists.boost.org

Sent: Thursday, June 05, 2008 4:12 AM

Subject: Re: A question about boost::bind function

Not sure why this was changed, though I've never used bind in this way (specifically, to bind to a reference of a member variable).

Are you free to make changes to the code? This should work in either version:

void AddUserAge( _sUserData& d ) { // <-- change this to a reference to the struct
    ++d.age;
}

int _tmain(int argc, _TCHAR* argv[])
{
    std::vector<_sUserData> vUserData;
    for( int i = 0; i < 10; ++i )
        vUserData.push_back( _sUserData() );
    std::for_each( vUserData.begin(), vUserData.end(), boost::bind( AddUserAge, _1 )); // <-- and remove the inner bind
    return 0;
}

Or you could just do this in 1.34.0 or higher:

#include <boost/foreach.hpp>
....

int _tmain(int argc, _TCHAR* argv[]) {
    std::vector<_sUserData> vUserData( 10 ); // vector of 10 _sUserData, default constructed
    BOOST_FOREACH( _sUserData& d, vUserData ) ++d.age;
    return 0;
}

Of course, all this is starting to look like a homework problem to me...

2008/6/3 风舞影天 <snwcwt@qq.com>:

I'm a newbie in boost library and sorry for my poor English.

 

I have a project now, it was created in Visual Studio.Net 2003 and the version of the boost library is 1.33.1, all thing is good. But, When I replaced the boost library with the new version 1.34.1 or 1.35.0,  the project can't compiled correct. The error message is 'can't convert const sometype& to sometype&'.  So, i force myself to read the source code of boost library and compare them betwwen version 1.33.1 and version 1.44.1. at last, I found the problem and written a test program. The following code is the test program:

 

#include "stdafx.h"

#include <boost/bind.hpp>
#include <vector>
#include <algorithm>

struct _sUserData
{
    int        m_nUserId;
    int        m_nUserAge;
    _sUserData()
        : m_nUserId( rand() )
        , m_nUserAge( rand()%100+1 )
    {
    }
};

void AddUserAge( int& age )
{
    ++age;
}

int _tmain(int argc, _TCHAR* argv[])
{
    std::vector<_sUserData> vUserData;
    for( int i = 0; i < 10; ++i )
        vUserData.push_back( _sUserData() );
    std::for_each( vUserData.begin(), vUserData.end(), boost::bind( AddUserAge, boost::bind( &_sUserData::m_nUserAge, _1 ) ) );
    return 0;
}

If i change the function AddUserAge( int& age ) to AddUserAge( const int& age ), all things is good. but I need change this parameter.

---

_______________________________________________
Boost-users mailing list
Boost-users@lists.boost.org
http://lists.boost.org/mailman/listinfo.cgi/boost-users