class XSemVer::SemVer

def self.parse_rubygems version_string
  if /v?(?<major>\d+)
       (\.(?<minor>\d+)
        (\.(?<patch>\d+)
         (\.(?<pre>[A-Za-z]+\.[0-9A-Za-z]+)
       )?)?)?
      /x =~ version_string
    major = major.to_i
    minor = minor.to_i if minor
    minor ||= 0
    patch = patch.to_i if patch
    patch ||= 0
    pre ||= ''
    SemVer.new major, minor, patch, pre, ''
  else
    SemVer.new
  end
end