From: Jeremy Bopp <jeremy@...>
Date: 2010-11-10T02:10:42+09:00
Subject: Re: bug in ruby 1.9.2-p0 gsub?

On 11/9/2010 11:03 AM, Sd He wrote:
> Why does the following only replace the first instance of the pattern?
> 
> '|\\ |\\ |'.gsub(/\|\\ \|/, "||")

The pattern is matching pairs of | characters with content in between.
Once it matches the first instance, there is only a single | character
remaining in the original string.  The replacement text is not taken
into consideration.

Try the following modification instead.  It uses a lookahead assertion
to avoid consuming the trailing | character in each sequence:

'|\\ |\\ |'.gsub(/\|\\ (?=\|)/, "|")

Since the search does not consume the trailing | character, the
replacement string is only a single | character rather than a double.

-Jeremy