class XSemVer::PreRelease

Represents the pre-release portion of a SemVer string.

def <=>(other)

Pre-release precedence is calculated using the following rules, which are listed above their corresponding code.
1.0.0-alpha < 1.0.0-alpha.1 < 1.0.0-beta.2 < 1.0.0-beta.11 < 1.0.0-rc.1 < 1.0.0.
The SemVer 2.0.0-rc2 spec uses this example for determining pre-release precedence: 
def <=>(other)
  
  # A SemVer with no prerelease data is 'greater' than a SemVer with any prerelease data.
  # If both prereleases are empty, they are equal.
  return  1 if  empty? && !other.empty?
  return -1 if !empty? &&  other.empty?
  return  0 if  empty? &&  other.empty?
  
  [ids.size, other.ids.size].max.times do |n|
    id = ids[n]
    oid = other.ids[n]
    
    # A pre-release with fewer ids is less than a pre-release with more ids. (1.0.0-alpha < 1.0.0-alpha.1)
    return 1 if oid.nil?
    return -1 if id.nil?
    
    # If a pre-release id consists of only numbers, it is compared numerically.
    if id =~ ONLY_DIGITS && oid =~ ONLY_DIGITS
      id = id.to_i
      oid = oid.to_i
    end
    
    # If a pre-release id contains one or more letters, it is compared alphabetically.
    comparison = (id <=> oid)
    return comparison unless comparison == 0
  end
  
  0
end

def empty? 

def empty?
  ids.empty?
end

def initialize(prerelease_string) 

def initialize(prerelease_string)
  @ids = prerelease_string.split(".")
end

def to_s 

def to_s
  ids.join "."
end