Re: [Boost-users] [lamba] Comparing return value of member functionwith ->*

From: Boris (boriss_at_[hidden])
Date: 2007-03-13 10:30:16

On Tue, 13 Mar 2007 00:21:36 +0200, Rodolfo Lima <rodolfo_at_[hidden]>  
wrote:

>> // Why doesn't this compile ...
>> std::for_each(from.begin(), from.end(), if_then((_1 ->* &sample::odd) ==
>> false, std::cout << _1));
>
> IMO it should be &1->*&sample::odd
>
> The ->* operator expects a pointer in its left side. Since & has higher
> priority than ->*, it suffices to add & to _l and it'll work.

I played around some more and even removed the comparison with false. But  
neither this ...

std::for_each(from.begin(), from.end(), if_then(boost::lambda::_1 ->*  
&sample::odd, std::cout << boost::lambda::_1));

... nor that ...

std::for_each(from.begin(), from.end(), if_then(&boost::lambda::_1 ->*  
&sample::odd, std::cout << boost::lambda::_1));

compiles. VC8++ complains about error C2451: conditional expression of  
type 'boost::lambda::detail::member_pointer_caller<RET,A,B>' is illegal.  
Everything works though with boost::lambda::bind. Why I don't know. From  
the documentation ->* looks like a more readable shortcut than  
boost::lambda::bind. There seem to be some limitations though (or does it  
depend on the compiler)?

Boris