Improve error message of matrix multiplication

1 files changed, 3 insertions, 3 deletions

diff --git a/polymatrix/expression/mixins/matrixmultexprmixin.py b/polymatrix/expression/mixins/matrixmultexprmixin.py
index 9402a19..2d86619 100644
--- a/polymatrix/expression/mixins/matrixmultexprmixin.py
+++ b/polymatrix/expression/mixins/matrixmultexprmixin.py
@@ -30,12 +30,12 @@ class MatrixMultExprMixin(ExpressionBaseMixin):
         state, left = self.left.apply(state=state)
         state, right = self.right.apply(state=state)
 
-        # assert left.shape[1] == right.shape[0], f'{left.shape[1]} is not equal to {right.shape[0]}'
-
         if not (left.shape[1] == right.shape[0]):
+            msg = f"Cannot multiply matrices {self.left} and {self.right} because their shapes " \
+                    f"{left.shape}, and {right.shape} do not match!"
             raise AssertionError(
                 to_operator_exception(
-                    message=f"{left.shape[1]} is not equal to {right.shape[0]}",
+                    message=msg,
                     stack=self.stack,
                 )
             )