Re: [boost] Re: TR2 and C++0x heads up

From: John Maddock (john_at_[hidden])
Date: 2005-04-23 04:43:17

> OTOH, since the first release I've felt the weakest elements of the 
> library
> have been the handling of local times and i/o.  It took a long time for me 
> to
> see 'the light' on i/o.  The first implementations of streaming facets 
> were
> just too clunky and were too hard for users to use and extend.  And the 
> bottom
> line is that every project/person/standard has their own format for 
> date-time
> i/o -- it's impossible to standardize what users want here.  Luckily last
> summer Martin Andrian showed me the light with a partial implementation of 
> a
> 'format string' based i/o facet (basically you can write:
> date_facet->format("%Y-%b-%d") to reset the format of a date in a stream).
> This approach solved a long standing issue on my standardization todo 
> list -->
> how does i/o fit in with the existing format string concepts in the 
> standard
> lib.  Not to mention that it is almost infinately flexible in terms of how 
> the
> various types can be streamed.  This code will be the standard i/o facet 
> in
> the 1.33 release.

Jeff, do you mind if I throw a wildcard in here?

Why not drop facets altogether and use a stream format manipulator instead:

std::cout << set_date_format("%Y-%b-%d") << mydate << std::endl;

The format would be stored in the iostreams iword/pword (that's what they're 
for).

You could still have a facet if you really wanted uses to change the 
*algorithm* used for io, but I guess what I'm trying to say is that:

algorithms go in facets.
configuration data goes in the iostream object itself.

Just my 2c worth,

Hope this doesn't cloud things up to much!

John.