Fix bug in Ruby implementation of WeightedChoice

Previous version of Ruby implementation of WeightedChoice did not work
correctly. New version has been verified to work correctly and has an
appropriate unit test.

alpha/ruby/lib/plan_out/op_random.rb

@@ -57,18 +57,19 @@ def simple_execute
 
       return [] if choices.length() == 0
 
-      cum_weights = choices.zip(weights)
+      cum_weights = Array.new(weights.length)
       cum_sum = 0.0
 
-      cum_weights.each do |choice, weight|
+      weights.each_with_index do |weight, index|
         cum_sum += weight
-        cum_weights[choice] = cum_sum
+        cum_weights[index] = cum_sum
       end
 
       stop_value = get_uniform(0.0, cum_sum)
 
-      cum_weights.each do |choice, cum_weight|
-        choice if stop_value <= cum_weight
+      i = 0
+      cum_weights.each_with_index do |cum_weight, index|
+        return choices[index] if stop_value <= cum_weight
       end
     end
   end
@@ -81,4 +82,4 @@ def simple_execute
       choices[rand_index]
     end
   end
-end
+end

alpha/ruby/test/plan_out/operator_test.rb

@@ -3,14 +3,24 @@
 module PlanOut
   class OperatorTest < Minitest::Test
     def setup
-      @operator = Operator.new({ foo: 'bar' })
-      @op_simple = OpSimple.new({ bar: 'qux' })
+      @a = Assignment.new('mtsalt')
     end
 
     def test_execute
-      a = Assignment.new('mtsalt')
-      assert_equal('mtsalt', @operator.execute(a))
-      assert_equal(-1, @op_simple.execute(a))
+      operator = Operator.new({ foo: 'bar' })
+      op_simple = OpSimple.new({ bar: 'qux' })
+      assert_equal('mtsalt', operator.execute(@a))
+      assert_equal(-1, op_simple.execute(@a))
+    end
+
+    def test_weighted_choice
+      weighted = WeightedChoice.new({
+        choices: ["c1", "c2", "c1"],
+        weights: [20, 40, 60],
+        unit: 42,
+        salt:'x'
+      })
+      assert_equal("c2", weighted.execute(@a))
     end
   end
-end
+end