Re: [Boost-users] Using lambda for sort

From: Peter Dimov (pdimov_at_[hidden])
Date: 2007-08-10 10:47:46

Olaf van der Spek wrote:
> On 8/9/07, Peter Dimov <pdimov_at_[hidden]> wrote:
>> Olaf van der Spek wrote:
>>
>>>>>       sort(countries1.begin(), countries1.end(),
>>>>> _1->second > _2->second);
>>
>>  sort( countries1.begin(), countries1.end(),
>>
>>   bind( &countries_t::value_type::second, *_1 )  > bind(
>> &countries_t::value_type::second, *_2 )
>
> Thanks, that did the trick. I didn't know you could use bind like this
> too. But why does the simpler syntax not work?

Due to the way operator-> overloading works, it's hard to make _1->second do 
what you want (and impossible for arbitrary identifiers and not just 
'second'.)

The closest you can get with Lambda is _1 ->* 
&countries_t::value_type::second.