[Boost-users] lambda / boost usage questions

From: Luis De la Parra (lparrab_at_[hidden])
Date: 2004-02-21 07:07:54

hello,
I don't have much experience with boost, so I'm having problems getting boost 
lambda to work...hope someone here can point me in the right direction.

I have:
class Song
{public:
        string artist( ) const { return m_artist }
        string title( )  const { return m_title }
 private:
        string m_artist, m_title;
}
typedef boost::shared_ptr<Song> pSong;
vector<pSong> c;

and I am trying to use lambda to find a song in c which matches a certain 
artist and title...something like

iterator it = find_if( c.begin(), c.end(), something )

but I havn't figured out what "something" should look like

I've  tried
find_if(begin(),end(), (_1->artist() == "a1" && _1->title = "t1" ) );
but the compiler -- or I =) -- doesn't seem to know the type of _1  
--> error: base operand of `->' has non-pointer type `const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >'

If I try
it = find_if(begin(),end(),  boost::bind(&Song::artist,_1)  == "a1"   );
it fails because "_1" is ambiguos (defined as lambda/placeholder and 
boost/arg )

using boost::lambda::bind  (and not including the "normal" bind ) gives a 
bunch cryptic errors...

I've tried several other variants with lambda / lambda::bind / boost::bind but 
I havn't figured it out... can anyone help me out?

I'd also like to know what's the difference between boost::bind and 
boost::lambda::bind ?
Also... is there a way to know when a lambda object is going to be 
constructed?, it's probably just that I don't know much about the BLL, but in 
cases where you have several nested lambdas and binds, I'm not sure which 
lambda objects will get constructed.

regards,

luis