class SemVer

def initialize major=0, minor=0, patch=0, special=''
  major.kind_of? Integer or raise "invalid major: #{major}"
  minor.kind_of? Integer or raise "invalid minor: #{minor}"
  patch.kind_of? Integer or raise "invalid patch: #{patch}"
  unless special.empty?
    special =~ /[A-Za-z][0-9A-Za-z\.]+/ or raise "invalid special: #{special}"
  end
  @major, @minor, @patch, @special = major, minor, patch, special
end