allow for rating single-rating teams

lib/rank_king.rb

@@ -13,7 +13,7 @@ module RankKing
       ratings = combo.map {|item| Rating.first(axis:, item:) || OS.rating }
       Math.sqrt(
         [ratings, ratings.reverse]
-          .map {|game| [game, OS.rate(game.map {[_1]}).flatten] }
+          .map {|game| [game, OS.rate(game).flatten] }
           .sum {|pre,post| pre.zip(post).sum { (_1.sigma - _2.sigma)**2 }}
       )
     }.last
@@ -23,7 +23,7 @@ module RankKing
     fail unless [winner, loser].all? { _1.pool == axis.pool }
 
     game = [winner, loser].map { Rating.first(axis:, item: _1) || OS.rating }
-    result = OS.rate(game.map { [_1] }).flatten
+    result = OS.rate(game).flatten
 
     DB.transaction do
       Ranking.create(axis:, winner:, loser:)

lib/rank_king/open_skill.rb

@@ -18,8 +18,10 @@ module RankKing
     end
 
     # TODO take an implicit array
-    # TODO array-ify elements
     def rate(teams)
+      # allow for passing in single-rating teams
+      teams = teams.map { Array(_1) }
+
       # tau keeps sigma from dropping too low so that ratings stay pliable
       # after many games
       tau_sq = @tau ** 2