From: Matt Armstrong <matt@...>
Date: 2002-12-14T01:25:21+09:00
Subject: Re: [RCR] Global Regexp Match Mechanism (//g)

nobu.nokada@softhome.net writes:

>>     (b) there is no way to anchor the regex at 'pos'
>> 
>>             "abcd".index(/\Abc/, 1) -> nil
>>             "abcd".index(/^bc/, 1)  -> nil
>
> "abcd".index(/\Gbc/, 1) -> 1

Great!  I didn't know you could do that.


>> Freezing the string is inconvenient in my application.  I examine a
>> string in detail before deciding whether to append more data to it
>> (String#<<) from a file or start a new string.
>
> Modification of target string will cause the character boundary
> issue even with your String#gpos.  It must be recalculated.

It is possible to be fancy and avoid recalculation of byte offset B of
character position C.  E.g. if you insert 10 bytes before B, increment
B by 10.

But your point about thread safety is good.  String#index together
with \G is a good solution.  Though Regexp#match with a character
offset may be handy too, since it returns the MatchData.