From: Joel VanderWerf <vjoel@...>
Date: 2008-05-09T09:00:26+09:00
Subject: Re: Doing an AND in regexp char class

Todd Benson wrote:
> On Thu, May 8, 2008 at 6:07 PM, ara.t.howard <ara.t.howard@gmail.com> wrote:
>> On May 8, 2008, at 3:40 PM, Todd Benson wrote:
>>> 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
>> cfp:~ > cat a.rb
>> class String
>>  def all_chars? chars
>>    tr(chars, '').empty?
>>  end
>> end
>>
>> p 'foobar'.all_chars?('rabof')
>> p 'foobar'.all_chars?('abc')
>> p 'foobar'.all_chars?('')
>>
>>
>>
>> cfp:~ > ruby a.rb
>> true
>> false
>> false
> 
> Cool :)  #tr is one of those useful methods I somehow consistently forget about.

But it can be done with regex, right? It's just more elegant with tr.

class String
   def all_chars? chars
     if chars.empty?
       empty?
     else
       /\A[#{chars}]*\z/ === self
     end
   end
end

p 'foobar'.all_chars?('rabof')  # => true
p 'foobar'.all_chars?('abc')    # => false
p 'foobar'.all_chars?('')       # => false

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407