Re: [Boost-users] [Proto] typeof in Hello World example

Subject: Re: [Boost-users] [Proto] typeof in Hello World example
From: Eric Niebler (eric_at_[hidden])
Date: 2010-11-15 10:56:56

On 11/15/2010 6:47 AM, Hossein Haeri wrote:
> Dear all,
> 
> I have recently started reading about Proto and am only crawling
> through the user guide. So, sorry if the question is too newbie...
> 
> I see in the Hello World example at the Getting Started section
> 
> http://boost.org/doc/libs/1_44_0/doc/html/proto/users_guide.html#boost_proto.users_guide.getting_started
>
>  in the Hello World example, the following header is also included:
> 
> <boost/typeof/std/ostream.hpp>

Correct.

> I was suspicious that this is not needed for this very example. So, I
> removed it and GCC 4.5.1 compiled it happily. I see also that this
> header is not included in the same example in the Example section of
> the user guide:
> 
> http://boost.org/doc/libs/1_44_0/doc/html/proto/users_guide.html#boost_proto.users_guide.examples

I should fix that.

>  Am I right in guessing that this header is not needed then?

No, it belongs there for portability, but it is not needed on all
compilers. Some older compilers don't have a decltype, typeof or
__typeof__ operator. On those compilers, types need to be registered
with the Boost.Typeof library, which provides emulation.

With gcc-4.5, you are free to disregard this include.

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com