Boundary and its opposite vertex iterator for the simplex tree

1 files changed, 23 insertions, 0 deletions

diff --git a/src/Simplex_tree/include/gudhi/Simplex_tree.h b/src/Simplex_tree/include/gudhi/Simplex_tree.h
index d48f6616..63a7f190 100644
--- a/src/Simplex_tree/include/gudhi/Simplex_tree.h
+++ b/src/Simplex_tree/include/gudhi/Simplex_tree.h
@@ -187,6 +187,12 @@ class Simplex_tree {
   typedef Simplex_tree_boundary_simplex_iterator<Simplex_tree> Boundary_simplex_iterator;
   /** \brief Range over the simplices of the boundary of a simplex. */
   typedef boost::iterator_range<Boundary_simplex_iterator> Boundary_simplex_range;
+  /** \brief Iterator over the simplices of the boundary and its opposite vertex of a simplex.
+   *
+   * 'value_type' is std::pair<Simplex_handle, Vertex_handle>. */
+  typedef Simplex_tree_boundary_opposite_vertex_simplex_iterator<Simplex_tree> Boundary_opposite_vertex_simplex_iterator;
+  /** \brief Range over the simplices of the boundary and its opposite vertex of a simplex. */
+  typedef boost::iterator_range<Boundary_opposite_vertex_simplex_iterator> Boundary_opposite_vertex_simplex_range;
   /** \brief Iterator over the simplices of the simplicial complex.
    *
    * 'value_type' is Simplex_handle. */
@@ -296,6 +302,23 @@ class Simplex_tree {
                                   Boundary_simplex_iterator(this));
   }
 
+  /** \brief Returns a range over the simplices of the boundary and its opposite vertex of a simplex.
+   *
+   * The boundary and its opposite vertex of a simplex is the set of codimension \f$1\f$ subsimplices of the simplex.
+   * If the simplex is \f$[v_0, \cdots ,v_d]\f$, with canonical orientation induced by \f$ v_0 < \cdots < v_d \f$, the
+   * iterator enumerates the simplices of the boundary in the order:
+   * \f$[v_0,\cdots,\widehat{v_i},\cdots,v_d]\f$ for \f$i\f$ from \f$0\f$ to \f$d\f$, where \f$\widehat{v_i}\f$ means
+   * that the vertex \f$v_i\f$ is omitted from boundary, but returned as the second element of the pair, known as the
+   * the opposite vertex of the boundary.
+   *
+   * @param[in] sh Simplex for which the boundary and its opposite vertex is computed.
+   * @return Iterator on a pair of SimplexHandle (a boundary) and a VertexHandle (its opposite vertex). */
+  template<class SimplexHandle>
+  Boundary_opposite_vertex_simplex_range boundary_opposite_vertex_simplex_range(SimplexHandle sh) {
+    return Boundary_opposite_vertex_simplex_range(Boundary_opposite_vertex_simplex_iterator(this, sh),
+                                                  Boundary_opposite_vertex_simplex_iterator(this));
+  }
+
   /** @} */  // end range and iterator methods
   /** \name Constructor/Destructor
    * @{ */