Re: [boost] Comment on string / unicode discussion

From: David Abrahams (dave_at_[hidden])
Date: 2006-07-06 14:25:05

"Robert Ramey" <ramey_at_[hidden]> writes:

> Then I wanted to compose them with a typedef
>
> typedef
>     boost::archive::iterators::insert_linebreaks<
>         boost::archive::iterators::base64_from_binary<
>             boost::archive::iterators::transform_width<
>                 const char *,
>                 6,
>                 8
>             >
>         >
>         ,72
>         ,const char // cwpro8 needs this
>     >
> base64_text;
>
> Wow - just great.  Now just construct an instance of base64_text - and we're
> in business.  So I can do:
>
> char * address; // pointer to character buffer
> ...
> boost::archive::iterators::ostream_iterator<char> oi(os);
> std::copy(
>     base64_text(address),
>     base64_text(
>         address + count
>     ),
>     oi
> );
>
> Uh - oh - I can do the above - because I need to instanciate the iterator 
> with
> some sort of make_???_iterator.   This an extra pain and adds a lot of 
> confusion
> It also prevents me from doing something like:
>
> std::copy(
>     wchar_from_mb(base64_text(address))),
>     wchar_from_mb((base64_text(
>         address + count
>     )),
>     oi
> );
>
> should I find this convenient.
>
> By adding the templated constructors and using them instead of 
> make_???_functions
> I was able to achieve what I desired.
>
>>> I've never been able to convince anyone else
>>> of the merit of the approach - but hope springs eternal.
>>
>> Maybe you never articulated sufficiently clearly what you added to the
>> basics provided by the iterator library, and why.
>
> LOL - apparently so.

Thanks; I think I see why you need the templated ctors now.

w.r.t. composing with a typedef, would

     boost::archive::iterators::insert_linebreaks<
         boost::archive::iterators::base64_from_binary<
             boost::archive::iterators::transform_width<
                 const char *,
                 6,
                 8
             >::type
        >::type
         ,72
         ,const char // cwpro8 needs this
     >::type
 base64_text;

be much worse, for your purposes?

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com