Convert String to Range

class String
 def to_range
     case self.count('.')
         when 2
             elements = self.split('..')
             return Range.new(elements[0].to_i, elements[1].to_i)
         when 3
             elements = self.split('...')
             return Range.new(elements[0].to_i, elements[1].to_i-1)
         else
             raise ArgumentError.new("Couldn't convert to Range:
#{str}")
     end
 end
end

p "1..2".to_range
p "1...2".to_range
p "1.2".to_range

output:
1..2
1..1
rng.test:11:in `to_range': undefined local variable or method `str'
for "1.2":String (NameError)
from rng.test:18

http://www.ruby-forum.com/topic/141926#629921