[boost] Re: Sorting list < shared_ptr < foo > > using std::list::sort()

From: Daniel Frey (daniel.frey_at_[hidden])
Date: 2003-04-24 05:23:31

HEATH DAVIS wrote:
> I have experienced some difficulty with sorting lists of type:
> 
> list < shared_ptr < foo > >
> 
 > [snip]
 >
> bool my_class::operator<(const my_class& arg)
> {
> return m_val < arg.m_val;
> }
> 
 > [snip]
> 
> //sort the list
> my_list.sort();

Here, you basically sort by using

shared_ptr::operator<

instead of

my_class::operator<

You need something like

template< T > struct shared_ptr_content_less
{
   bool operator()( const boost::shared_ptr< T >& lhs,
                    const boost::shared_ptr< T >& rhs ) const
   {
     return *lhs < *rhs;
   }
};

and call

my_list.sort( shared_ptr_content_less< my_list >() );

The code is untested, but I hope you get the idea. Also, there might be 
some easier way using other boost-libs to create the helper on-the-fly, 
but others definitely know better than me :)

Regards, Daniel

-- 
Daniel Frey
aixigo AG - financial training, research and technology
Schloß-Rahe-Straße 15, 52072 Aachen, Germany
fon: [phone], fax: [phone]
eMail: daniel.frey_at_[hidden], web: http://www.aixigo.de