Doing an AND in regexp char class

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Doing an AND in regexp char class
\ Todd Benson (8 May 2008)
. \ ara.t.howard (8 May 2008)
. . \ Todd Benson (8 May 2008)
. . . \ ara.t.howard (8 May 2008)
. . . . \ Robert Dober (9 May 2008)
. . . \ Joel VanderWerf (9 May 2008)
. . . . \ Todd Benson (9 May 2008)
. . . . . \ Joel VanderWerf (9 May 2008)
. . . . . . \ David A. Black (9 May 2008)
. . . . . . . \ Joel VanderWerf (9 May 2008)
. . . . . . . . \ David A. Black (9 May 2008)
. . . . . . \ Todd Benson (9 May 2008)
. . . . . \ David A. Black (9 May 2008)
. . . . \ 7stud -- (9 May 2008)
. . . . . \ David A. Black (9 May 2008)
. . . . . . \ 7stud -- (9 May 2008)
. . \ Pit Capitain (11 May 2008)
. \ Rick DeNatale (8 May 2008)

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Subject:	Doing an AND in regexp char class
Group:	Ruby-talk
From:	Todd Benson
Date:	8 May 2008

This question arises out of a couple of recent threads and may or may
not be a Ruby-specific question.

I can check with a character class if one of the characters in the
class exists or does not exist, but can I use a regexp to check if a
string absolutely contains all of the characters in the class?

Using a set perspective, I can do it like this in irb...

s1 = "hello there"
s2 = "ohi"
(s2.unpack('c*') & s1.unpack('c*')).size == s2.size

=> false

I use unpack to avoid creating a bunch of String objects, one for each
element in the array, which would happen if I used #split. What I'm
wondering is if there is a way to do this with a simple regexp.

Thanks,
Todd