# File lib/sup/contact.rb, line 6
  def initialize fn
    @fn = fn

    ## maintain the mapping between people and aliases. for contacts without
    ## aliases, there will be no @a2p entry, so @p2a.keys should be treated
    ## as the canonical list of contacts.

    @p2a = {} # person to alias
    @a2p = {} # alias to person

    if File.exists? fn
      IO.foreach(fn) do |l|
        l =~ /^([^:]*): (.*)$/ or raise "can't parse #{fn} line #{l.inspect}"
        aalias, addr = $1, $2
        p = Person.from_address addr
        @p2a[p] = aalias
        @a2p[aalias] = p unless aalias.nil? || aalias.empty?
      end
    end
  end