Hi --

On Fri, 9 May 2008, Joel VanderWerf wrote:

>  Todd Benson wrote:
> > I'm drawing a blank here with this one.  Why doesn't this work then...
> > 
> > irb(main):006:0> r = /\A[oh]*\z/
> > => /\A[oh]*\z/
> > irb(main):007:0> s = "hello, there"
> > => "hello, there"
> > irb(main):008:0> r === s
> > => false
> 
>  Maybe I'm confused about was wanted originally. The above tests the following 
>  condition:
> 
>   (set of chars occurring in given string)
>      is_a_subset_of
>   (given set of chars).
> 
>  irb(main):007:0> /\A[oh]*\z/ === "hohoho"
>  => true
>  irb(main):008:0> /\A[oh]*\z/ === "ho ho"
>  => false
> 
>  If you want superset instead of subset, this works:
> 
>  irb(main):013:0> /(?=.*h)(?=.*o)/ === "h o"
>  => true

That depends on the order, though. To do the superset test, you could
just do the subset, but in the other direction: check that the
character class, as a string, doesn't contain anything that isn't in
the main string:

   str = "h o"
   chars = "ho"

   /\A[#{str}]*\z/ === chars    # true

(though probably best to uniquify the string first).


David

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