Added list of changes submitted by Jeff Rose <jeff@rosejn.net>.

[rubyvote] / lib / rubyvote / positional.rb

diff --git a/lib/rubyvote/positional.rb b/lib/rubyvote/positional.rb
new file mode 100644 (file)
index 0000000..11e8a49
--- /dev/null
+++ b/lib/rubyvote/positional.rb
@@ -0,0 +1,74 @@
+# election library -- a ruby library for elections
+# copyright © 2005 MIT Media Lab and Benjamin Mako Hill
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301, USA.
+
+#################################################################
+## ==== positional.rb ====
+##
+## This file contains positional election methods. Currently only
+## includes an implementation of the Borda count election method.
+#################################################################
+
+##################################################################
+## BordaVote and BordaResult Classes
+##
+## These classes inherit from and/or are modeled after the classes in
+## election.rb and condorcet.rb
+
+class BordaVote < ElectionVote
+
+  def initialize(votes=nil)
+    @candidates = Array.new
+    votes.each do |vote|
+      @candidates = vote.uniq if vote.uniq.length > candidates.length
+    end
+    super(votes)
+  end
+
+  def tally_vote(vote)
+    points = candidates.length - 1
+    vote.each do |candidate|
+      @votes[candidate] = points
+      points -= 1
+    end
+  end
+
+  def verify_vote(vote=nil)
+    vote.instance_of?( Array ) and
+      vote == vote.uniq
+  end
+
+  def result
+    BordaResult.new(self)
+  end
+end
+
+class BordaResult < ElectionResult
+  def initialize(voteobj=nil)
+    super(voteobj)
+    votes = @election.votes
+
+    @ranked_candidates = votes.sort do |a, b|
+      b[1] <=> a[1]
+    end.collect {|i| i[0]}
+
+    @winners = @ranked_candidates.find_all do |i|
+      votes[i] == votes[@ranked_candidates[0]]
+    end
+  end
+
+end