Re: [Boost-users] [regex] Boost.Regex + ICU vs. standalone ICU

Subject: Re: [Boost-users] [regex] Boost.Regex + ICU vs. standalone ICU
From: AJG (plus.ajg_at_[hidden])
Date: 2010-09-26 16:30:12

John Maddock <boost.regex <at> virgin.net> writes:
> The new stuff in Perl-5.10 and supported in Boost.Regex are:
> 
> Named sub-expressions: 
> 
http://www.boost.org/doc/libs/1_44_0/libs/regex/doc/html/boost_regex/syntax/perl
_syntax.html#boost_regex.syntax.perl_syntax.named_subexpressions
> 
> Branch resets: 
> 
http://www.boost.org/doc/libs/1_44_0/libs/regex/doc/html/boost_regex/syntax/perl
_syntax.html#boost_regex.syntax.perl_syntax.branch_reset
> 
> Recursion: 
> 
http://www.boost.org/doc/libs/1_44_0/libs/regex/doc/html/boost_regex/syntax/perl
_syntax.html#boost_regex.syntax.perl_syntax.recursive_expressions
> 
> Conditional on recursion or subexpression match: 
> 
http://www.boost.org/doc/libs/1_44_0/libs/regex/doc/html/boost_regex/syntax/perl
_syntax.html#boost_regex.syntax.perl_syntax.conditional_expressions
> 
> The (*OPERATOR) syntax introduced in Perl-5.10 is not currently supported.
> 
> HTH, John. 

That's fantastic, thank you. I have an unrelated Boost.Regex question: how 
expensive are basic_regex objects to copy? Say, relative to constructing (and 
thus reparsing) from a string pattern, anew?

The reason I ask is because I have a variant type with several value types, 
including a regex type. I was wondering whether it makes more sense to store the 
regex pattern in that variant as a string, and to construct the actual 
basic_regex from that string every time I need to operate on it, or to store it 
as a basic_regex and hope that copies are not too expensive. One other 
alternative is to store the regex on the heap using a smart pointer, but I'd 
rather keep value semantics so long as performance isn't an issue.

(Oh, incidentally, does Boost.Regex have support for Boost.Serialization? Right 
now what I do is serialize it [the pattern] as an std::string -- is that the 
recommended approach?)

Thanks!