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diff --git a/src/Coxeter_triangulation/include/gudhi/Permutahedral_representation/Simplex_comparator.h b/src/Coxeter_triangulation/include/gudhi/Permutahedral_representation/Simplex_comparator.h
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+/*    This file is part of the Gudhi Library - https://gudhi.inria.fr/ - which is released under MIT.
+ *    See file LICENSE or go to https://gudhi.inria.fr/licensing/ for full license details.
+ *    Author(s):       Siargey Kachanovich
+ *
+ *    Copyright (C) 2019 Inria
+ *
+ *    Modification(s):
+ *      - YYYY/MM Author: Description of the modification
+ */
+
+#ifndef PERMUTAHEDRAL_REPRESENTATION_SIMPLEX_COMPARATOR_H_
+#define PERMUTAHEDRAL_REPRESENTATION_SIMPLEX_COMPARATOR_H_
+
+namespace Gudhi {
+
+namespace coxeter_triangulation {
+
+/** \class Simplex_comparator
+ *  \brief A comparator class for Permutahedral_representation.
+ *   The comparison is in lexicographic order first on
+ *   vertices and then on ordered partitions with sorted parts.
+ *   The lexicographic order forces that any face is larger than
+ *   a coface.
+ *
+ *  \tparam Permutahdral_representation_ Needs to be
+ *   Permutahedral_representation<Vertex_, Ordered_set_partition_>
+ *
+ *  \ingroup coxeter_triangulation
+ */
+template <class Permutahedral_representation_>
+struct Simplex_comparator {
+  /** \brief Comparison between two permutahedral representations.
+   *  Both permutahedral representations need to be valid and
+   *  the vertices of both permutahedral representations need to be of the same size.
+   */
+  bool operator()(const Permutahedral_representation_& lhs, const Permutahedral_representation_& rhs) const {
+    if (lhs.vertex() < rhs.vertex()) return true;
+    if (lhs.vertex() > rhs.vertex()) return false;
+
+    if (lhs.partition().size() > rhs.partition().size()) return true;
+    if (lhs.partition().size() < rhs.partition().size()) return false;
+
+    if (lhs.partition() < rhs.partition()) return true;
+    if (lhs.partition() > rhs.partition()) return false;
+
+    return false;
+  }
+};
+
+}  // namespace coxeter_triangulation
+
+}  // namespace Gudhi
+
+#endif