Re: [Boost-users] Defining less on member variables/functions

Duane Murphy wrote:

--- At Fri, 26 Mar 2004 00:48:49 +0100, Daniel Wallin wrote:

...

struct X { int a; };

std::vector<X> v;

With boost.bind:

std::sort( v.begin() , v.end() , boost::bind( std::less<int>() , boost::bind(&X::a, _1) , boost::bind(&X::a, _2) ) );

I don't know lambda, so I won't comment on that. But, I thought that the first parameter to bind was a function pointer? You can bind to an address?

Please explain how this works?

&X::a is not an address. It is a member pointer. boost::bind allows you to work with pointers to members as if they were function objects. It does this by automatically translating &X::a to boost::mem_fn(&X::a).