More review comments in expression mixins

1 files changed, 2 insertions, 0 deletions

diff --git a/polymatrix/expression/mixins/additionexprmixin.py b/polymatrix/expression/mixins/additionexprmixin.py
index bc83ff3..200c328 100644
--- a/polymatrix/expression/mixins/additionexprmixin.py
+++ b/polymatrix/expression/mixins/additionexprmixin.py
@@ -44,6 +44,8 @@ class AdditionExprMixin(ExpressionBaseMixin):
 
         poly_matrix_data = {}
 
+        # NP: this code is very old I presume, so it iterates over zero entries
+        # FIXME: iterate only over non-zero entries
         for row in range(left.shape[0]):
             for col in range(left.shape[1]):
                 poly_data = {}