From: Janus Bor <janus@...>
Date: 2008-08-16T10:56:26+09:00
Subject: [Regex] Alternative for look behind

Hi all,

I need to replace all '-' characters at the beginning of a sequence
(string) with 'X's (until a character appears that is not '-').

E.g.

-------abcde-gh----

should be changed into

XXXXXXXabcde-gh----



If Ruby would support look behind in Regular Expressions, I could
probably do something like this:

sequence.gsub(/(?=^-*)-/, "X")

But unfortunately Ruby does not support look behind.

Of course, I could count the number of '-' at the beginning of the
sequence:

x = sequence[/-*/].length

And then I could replace the first x characters with "X". But I don't
like that solution, it feels clumsy. Is there an elegant way of doing
this?

Thanks in advance & best regards!
 Janus
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