[Boost-users] Re: regex_search (v4) raises exception for wregex

From: Eric Niebler (eric_at_[hidden])
Date: 2004-05-03 15:15:40

John Maddock wrote:
>>i think, "(one|two|three|)" style alternation (notice the empty string on
>>the right) should be accepted and handled as "(one|two|three)?"
>>now it throws bad_expression
> 
> 
> I'm not sure about this one, Boost.regex has always deliberately rejected
> that, and although I realise that perl5 does accept this, perl6 will regard
> it as an error I believe.
> 

Indeed, this will be an error in perl 6. See "Null String Reform" at 
http://www.perl.com/pub/a/2002/06/04/apo5.html?page=10. You will have to 
write this as (one|two|three|<null>).

I think it would be a horrible mistake for (one|two|three|) to be 
handled as (one|two|three). Either accept it for what it is or reject 
it, but don't try to second-guess what the programmer really meant.

--
Eric Niebler
Boost Consulting
www.boost-consulting.com