From: Matthew Kerwin <matthew@...>
Date: 2012-10-18T09:51:47+09:00
Subject: Re: Drop 1st and last particular character

Tangentially, it just occurred to me that ruby's regular expression
engine does the same thing that  javascript's does, when globally
replacing /X*$/ .  It arose when someone wanted to replace any number
(or none) of a character at the start and end of a string with exactly
one of that character.

irb(main):001:0> 'foo'.gsub(/\A#*|#*\Z/, '#')
=> "#foo#"
irb(main):002:0> '#foo'.gsub(/\A#*|#*\Z/, '#')
=> "#foo#"
irb(main):003:0> '##foo'.gsub(/\A#*|#*\Z/, '#')
=> "#foo#"
irb(main):004:0> 'foo#'.gsub(/\A#*|#*\Z/, '#')
=> "#foo##"
irb(main):005:0> 'foo##'.gsub(/\A#*|#*\Z/, '#')
=> "#foo##"
irb(main):006:0> '##foo##'.gsub(/\A#*|#*\Z/, '#')
=> "#foo##"

The original javascript question came up on StackOverflow
<http://stackoverflow.com/questions/6147609/how-to-remove-duplicate-character-at-the-end-of-a-string-in-regex>

I blogged about it here:
http://matthew.kerwin.net.au/blog/20110608_javascript_global_regexp


-- 
  Matthew Kerwin, B.Sc (CompSci) (Hons)
  http://matthew.kerwin.net.au/
  ABN: 59-013-727-651

  "You'll never find a programming language that frees
  you from the burden of clarifying your ideas." - xkcd