From c5786c05ec4ae789a9894b9b7c58ebb2a5ad2b78 Mon Sep 17 00:00:00 2001
From: saidctb <said-ctb@live.fr>
Date: Thu, 23 Jan 2020 19:12:43 +0100
Subject: [PATCH] treat object of class Idx in SymbolicExpr

---
 sympde/topology/mapping.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sympde/topology/mapping.py b/sympde/topology/mapping.py
index b7901859..4d5a8720 100644
--- a/sympde/topology/mapping.py
+++ b/sympde/topology/mapping.py
@@ -2,7 +2,7 @@
 
 from collections  import OrderedDict
 
-from sympy import Indexed, IndexedBase, Matrix, ImmutableDenseMatrix
+from sympy import Indexed, IndexedBase, Idx, Matrix, ImmutableDenseMatrix
 from sympy import Function
 from sympy import sympify
 from sympy.core import Basic
@@ -851,6 +851,9 @@ def eval(cls, *_args, **kwargs):
         elif isinstance(expr, Indexed):
             return expr
 
+        elif isinstance(expr, Idx):
+            return expr
+
         elif isinstance(expr, Function):
             return expr