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

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-03-26 13:42:51

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).