From: Erik Terpstra <erik@...>
Date: 2004-05-13T17:38:51+09:00
Subject: How to make combinations of an array to produce all possible expressions?

I have an array 'conds', which contains some sub-expressions for an 
xpath query:

   conds = ["@title='Foo'", "@edition='Bar'", "@date='20040513'"]

Is there an existing library that lets me construct all possible 
combinations like this?

   puts conds.<some Array extension method>.collect{|n| n.join ' and '}

which produces:

@title='Foo' and @edition='Bar' and @date='20040513'
@title='Foo' and @edition='Bar'
@title='Foo' and @date='20040513'
@edition='Bar' and @date='20040513'
@title='Foo'
@edition='Bar'
@date='20040513'