[Boost-users] Multi Index with BOOST_AUTO question.

[Surya Kiran Gullapalli]

Hello all,

I'm a newbie to multi-index. I ran into a strange problem with VS2008. When using BOOST_AUTO with multi-index I'm getting compilation errors (C2248) . Please see the following code.

<snip>

#include <iostream>

#include <string>

using namespace std ;

#include <boost/multi_index_container.hpp>

#include <boost/multi_index/mem_fun.hpp>

#include <boost/multi_index/ordered_index.hpp>

#include <boost/multi_index/identity.hpp>

#include <boost/multi_index/member.hpp>

#include <boost/foreach.hpp>

#include <boost/typeof/typeof.hpp>

using namespace boost ;

using namespace boost::multi_index ;

class Test

{

friend bool operator< (const Test& p_lhs, const Test& p_rhs)

{ return p_lhs._i < p_rhs._i ; }

friend ostream& operator << (ostream& os, const Test& p_test)

{

os << "Integer: " << p_test._i << "\tString: " << p_test._s ; 

return os ;

}

private:

int _i ;

string _s ;

public:

Test (int i, string s): _i(i), _s(s) { }

string getString (void) const { return _s ; }

} ;

struct byNumber { } ;

struct byString { } ;

int main (void)

{

typedef

multi_index_container <Test, indexed_by <

ordered_unique<tag<byNumber>, identity <Test> >

, ordered_non_unique < tag<byString>, BOOST_MULTI_INDEX_CONST_MEM_FUN(Test, string, getString) >

> > Container ;

typedef Container::index<byNumber>::type TestByNumber ;

typedef Container::index<byString>::type TestByString ;

Container c ;

c.insert (Test(5, "Surya")) ;

c.insert (Test(15, "Kiran")) ;

//TestByNumber& tests = c.get<byNumber>() ;

BOOST_AUTO(tests, c.get<byNumber>()) ;

BOOST_FOREACH (Test t, tests)

cout << t << endl ;

return 0 ;

}

</snip>

Compilation for this case fails with C2248. If I replace the BOOST_AUTO with the previous line's statement, compilation goes well. This happens with VS2008 only. with VS2005, there's no issue with BOOST_AUTO.

Am I missing something here?

Thanks,

Surya

[Igor R]

BOOST_AUTO(tests, c.get<byNumber>()) ;

 

try:

BOOST_AUTO(&tests, c.get<byNumber>()) ;

[Surya Kiran Gullapalli]

Thanks,

It worked. What is the difference ?. Which is correct ?

Surya 

[Igor R]

It worked. What is the difference ?. Which is correct ?

 

BOOST_AUTO(a, A) ; // is A a;

BOOST_AUTO(&a, A) ; // is A &a;

 

Since you can't copy the index, you should define a reference.

[Surya Kiran Gullapalli]

I got that. I've looked at Boost.Typeof documentation. But why was it working with VS2005 ?

Thanks,

Surya

[Igor R]

I got that. I've looked at Boost.Typeof documentation. But why was it working with VS2005 ?

 

 

Because in VS2005 index copying was not blocked (due to some compiler limitations) - it just would cause a crash in any subsequent operation with that copy :).

[Igor R]

look at this thread:

http://lists.boost.org/boost-users/2008/07/37788.php