Indexed: ensure that __new__ returns a new instance

ufl/core/multiindex.py

@@ -62,9 +62,7 @@ def __hash__(self):
 
     def __eq__(self, other):
         """Check equality."""
-        if isinstance(other, FixedIndex):
-            other = int(other)
-        return isinstance(other, int) and int(self) == other
+        return isinstance(other, (FixedIndex, int)) and int(self) == int(other)
 
     def __int__(self):
         """Convert to int."""
@@ -164,7 +162,7 @@ def indices(self):
 
     def _ufl_compute_hash_(self):
         """Compute UFL hash."""
-        return hash(("MultiIndex",) + tuple(hash(ind) for ind in self._indices))
+        return hash(("MultiIndex", *map(hash, self._indices)))
 
     def __eq__(self, other):
         """Check equality."""
@@ -238,7 +236,7 @@ def __radd__(self, other):
 
     def __str__(self):
         """Format as a string."""
-        return ", ".join(str(i) for i in self._indices)
+        return ", ".join(map(str, self._indices))
 
     def __repr__(self):
         """Return representation."""

ufl/core/operator.py

@@ -39,7 +39,7 @@ def _ufl_signature_data_(self):
 
     def _ufl_compute_hash_(self):
         """Compute a hash code for this expression. Used by sets and dicts."""
-        return hash((self._ufl_typecode_,) + tuple(map(hash, self.ufl_operands)))
+        return hash((self._ufl_typecode_, *map(hash, self.ufl_operands)))
 
     def __repr__(self):
         """Default repr string construction for operators."""

ufl/indexed.py

@@ -47,7 +47,8 @@ def __new__(cls, expression, multiindex):
 
         try:
             # Simplify indexed ListTensor
-            return expression[multiindex]
+            c = expression[multiindex]
+            return Indexed(*c.ufl_operands) if isinstance(c, Indexed) else c
         except ValueError:
             return Operator.__new__(cls)