Handle different lset elements in lset#group_count

lib/bud/lattice-lib.rb

@@ -252,8 +252,15 @@ def inspect
     # Assume key_cols for now gives indices
     rv = Hash.new(Bud::MaxLattice.new(0))
     @v.each do |t|
+      unless t.class == Array
+        raise Bud::TypeError, "group_count only works if lset elements are type Array"
+      end
+
       key = []
       key_cols.each do |ind|
+        if ind >= t.length
+          raise Bud::Error, "lset element in group_count does not have column index #{ind}"
+        end
         key << t[ind]
       end
       rv[key] += 1

test/tc_lattice.rb

@@ -1213,6 +1213,23 @@ def test_set_multiple_groupcnt
     assert_equal(expected, i.res.current_value.reveal)
   end
 
+  def test_set_error_groupcnt
+    i = SetSimpleGroupCnt.new
+    i.tick
+
+    i.s1 <+ ['a1']
+    assert_raises(Bud::TypeError) do
+      i.tick
+    end
+
+    i = SetSimpleGroupCnt.new
+    i.tick
+    i.s1 <+ [['a1', 1], []]
+    assert_raises(Bud::Error) do
+      i.tick
+    end
+  end
+
   def test_set_product
     i = SetProduct.new
     i.tick