Re: [boost] [regex] format_perl conundrum

From: John Maddock (john_at_[hidden])
Date: 2007-03-20 05:51:17

Eric Niebler wrote:

> To be honest, I find the need for the hacks you describe above to be a
> bit distasteful. Any vendor who wants format_perl-like behavior will
> route around the damage in the RegexTraits concept. A better (?)
> design might have to been to go whole-hog with locales and facets,
> and define some standard regex traits facets that basic_regex<> and
> match_results<> can query for at runtime. Eg.: If a regex-trait
> version-2 facet isn't installed, try for version-1, then defer to the
> ctype and collate facets, etc. And the traits doesn't need to be part
> of the basic_regex<> type (it isn't in xpressive). C-compatibility
> could have been maintained by providing a ctype facet that is
> implemented in terms of the global C locale. The whole RegexTraits
> concept and version tags seem like wheel reinvention to me.
>
> Just thinking out loud,

Think all you like: it's fair comment.  Actually the original regex 
implementation used a custom facet installed in the locale rather than a 
traits class: but broken and poorly behaved locale implementations caused me 
so much hassle that in the end I gave up and used a traits class instead 
:-(  Use of a traits class also makes it easier IMO to use non-std locale 
mechanisms (the Win32 API's or ICU's locale support) if you want to.

Still learning yours.... John.