remove polymatrix entry when two entries add up to zero

1 files changed, 6 insertions, 1 deletions

diff --git a/polymatrix/expression/mixins/additionexprmixin.py b/polymatrix/expression/mixins/additionexprmixin.py
index c4f3113..20ff5d0 100644
--- a/polymatrix/expression/mixins/additionexprmixin.py
+++ b/polymatrix/expression/mixins/additionexprmixin.py
@@ -1,6 +1,7 @@
 
 import abc
 import collections
+import math
 import typing
 import dataclass_abc
 
@@ -83,7 +84,11 @@ class AdditionExprMixin(ExpressionBaseMixin):
                             else:
                                 terms_row_col[monomial] += value
 
-                terms[row, col] = terms_row_col
+                                if math.isclose(terms_row_col[monomial], 0):
+                                    del terms_row_col[monomial]
+
+                if 0 < len(terms_row_col):
+                    terms[row, col] = terms_row_col
 
         poly_matrix = init_poly_matrix(
             terms=terms,