From 32ac46b376648e1daf4b15dfadc6c3c4e9f77354 Mon Sep 17 00:00:00 2001
From: Pablo Brubeck <brubeck@protonmail.com>
Date: Thu, 2 Jan 2025 09:00:21 -0600
Subject: [PATCH] Implement empty() for BaseForm subclasses

---
 ufl/algorithms/formsplitter.py | 10 ++++------
 ufl/form.py                    | 10 +++++++++-
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/ufl/algorithms/formsplitter.py b/ufl/algorithms/formsplitter.py
index 7ab0f6a1e..a81176b5c 100644
--- a/ufl/algorithms/formsplitter.py
+++ b/ufl/algorithms/formsplitter.py
@@ -10,6 +10,8 @@
 
 from typing import Optional
 
+import numpy as np
+
 from ufl.algorithms.map_integrands import map_expr_dag, map_integrand_dags
 from ufl.argument import Argument
 from ufl.classes import FixedIndex, ListTensor
@@ -53,14 +55,10 @@ def argument(self, obj):
                 Q_i = FunctionSpace(dom, sub_elem)
                 a = Argument(Q_i, obj.number(), part=obj.part())
 
-                indices = [()]
-                for m in a.ufl_shape:
-                    indices = [(*k, j) for k in indices for j in range(m)]
-
                 if i == self.idx[obj.number()]:
-                    args.extend(a[j] for j in indices)
+                    args.extend(a[j] for j in np.ndindex(a.ufl_shape))
                 else:
-                    args.extend(Zero() for j in indices)
+                    args.extend(Zero() for j in np.ndindex(a.ufl_shape))
 
             return as_vector(args)
 
diff --git a/ufl/form.py b/ufl/form.py
index c4b672330..0560dd0f7 100644
--- a/ufl/form.py
+++ b/ufl/form.py
@@ -307,7 +307,7 @@ def integrals_by_domain(self, domain):
 
     def empty(self):
         """Returns whether the form has no integrals."""
-        return self.integrals() == ()
+        return len(self.integrals()) == 0
 
     def ufl_domains(self):
         """Return the geometric integration domains occuring in the form.
@@ -812,6 +812,10 @@ def equals(self, other):
             a == b for a, b in zip(self.components(), other.components())
         )
 
+    def empty(self):
+        """Returns whether the FormSum has no components."""
+        return len(self.components()) == 0
+
     def __str__(self):
         """Compute shorter string representation of form. This can be huge for complicated forms."""
         # Warning used for making sure we don't use this in the general pipeline:
@@ -878,6 +882,10 @@ def ufl_domains(self):
             self._analyze_domains()
         return self._domains
 
+    def empty(self):
+        """Returns whether the form has no integrals."""
+        return True
+
     def __ne__(self, other):
         """Overwrite BaseForm.__neq__ which relies on `equals`."""
         return not self == other