A fix proposal for boudaries of a simplex python version

5 files changed, 49 insertions, 0 deletions

diff --git a/src/Simplex_tree/include/gudhi/Simplex_tree/Simplex_tree_iterators.h b/src/Simplex_tree/include/gudhi/Simplex_tree/Simplex_tree_iterators.h
index 9007b6bd..9c864454 100644
--- a/src/Simplex_tree/include/gudhi/Simplex_tree/Simplex_tree_iterators.h
+++ b/src/Simplex_tree/include/gudhi/Simplex_tree/Simplex_tree_iterators.h
@@ -85,6 +85,11 @@ class Simplex_tree_boundary_simplex_iterator : public boost::iterator_facade<
   typedef typename SimplexTree::Vertex_handle Vertex_handle;
   typedef typename SimplexTree::Siblings Siblings;
 
+  Simplex_tree_boundary_simplex_iterator()
+      : sib_(nullptr),
+        st_(nullptr)  {
+  }
+
 // any end() iterator
   explicit Simplex_tree_boundary_simplex_iterator(SimplexTree * st)
       : last_(st->null_vertex()),
diff --git a/src/python/gudhi/simplex_tree.pxd b/src/python/gudhi/simplex_tree.pxd
index e748ac40..a64599e7 100644
--- a/src/python/gudhi/simplex_tree.pxd
+++ b/src/python/gudhi/simplex_tree.pxd
@@ -36,6 +36,12 @@ cdef extern from "Simplex_tree_interface.h" namespace "Gudhi":
         Simplex_tree_skeleton_iterator operator++() nogil
         bint operator!=(Simplex_tree_skeleton_iterator) nogil
 
+    cdef cppclass Simplex_tree_boundary_iterator "Gudhi::Simplex_tree_interface<Gudhi::Simplex_tree_options_full_featured>::Boundary_simplex_iterator":
+        Simplex_tree_boundary_iterator() nogil
+        Simplex_tree_simplex_handle& operator*() nogil
+        Simplex_tree_boundary_iterator operator++() nogil
+        bint operator!=(Simplex_tree_boundary_iterator) nogil
+
 
     cdef cppclass Simplex_tree_interface_full_featured "Gudhi::Simplex_tree_interface<Gudhi::Simplex_tree_options_full_featured>":
         Simplex_tree() nogil
@@ -65,6 +71,8 @@ cdef extern from "Simplex_tree_interface.h" namespace "Gudhi":
         vector[Simplex_tree_simplex_handle].const_iterator get_filtration_iterator_end() nogil
         Simplex_tree_skeleton_iterator get_skeleton_iterator_begin(int dimension) nogil
         Simplex_tree_skeleton_iterator get_skeleton_iterator_end(int dimension) nogil
+        Simplex_tree_boundary_iterator get_boundary_iterator_begin(vector[int] simplex) nogil
+        Simplex_tree_boundary_iterator get_boundary_iterator_end(vector[int] simplex) nogil
 
 cdef extern from "Persistent_cohomology_interface.h" namespace "Gudhi":
     cdef cppclass Simplex_tree_persistence_interface "Gudhi::Persistent_cohomology_interface<Gudhi::Simplex_tree<Gudhi::Simplex_tree_options_full_featured>>":
diff --git a/src/python/gudhi/simplex_tree.pyx b/src/python/gudhi/simplex_tree.pyx
index 20e66d9f..da445a12 100644
--- a/src/python/gudhi/simplex_tree.pyx
+++ b/src/python/gudhi/simplex_tree.pyx
@@ -285,6 +285,22 @@ cdef class SimplexTree:
             ct.append((v, filtered_simplex.second))
         return ct
 
+    def get_boundaries(self, simplex):
+        """This function returns a generator with the boundaries of a given N-simplex.
+
+        :param simplex: The N-simplex, represented by a list of vertex.
+        :type simplex: list of int.
+        :returns:  The (simplices of the) boundaries of a simplex
+        :rtype:  generator with tuples(simplex, filtration)
+        """
+        cdef Simplex_tree_boundary_iterator it =  self.get_ptr().get_boundary_iterator_begin(simplex)
+        cdef Simplex_tree_boundary_iterator end = self.get_ptr().get_boundary_iterator_end(simplex)
+
+        while it != end:
+            yield self.get_ptr().get_simplex_and_filtration(dereference(it))
+            preincrement(it)
+
+
     def remove_maximal_simplex(self, simplex):
         """This function removes a given maximal N-simplex from the simplicial
         complex.
diff --git a/src/python/include/Simplex_tree_interface.h b/src/python/include/Simplex_tree_interface.h
index 56d7c41d..c4f18eeb 100644
--- a/src/python/include/Simplex_tree_interface.h
+++ b/src/python/include/Simplex_tree_interface.h
@@ -36,6 +36,7 @@ class Simplex_tree_interface : public Simplex_tree<SimplexTreeOptions> {
   using Skeleton_simplex_iterator = typename Base::Skeleton_simplex_iterator;
   using Complex_simplex_iterator = typename Base::Complex_simplex_iterator;
   using Extended_filtration_data = typename Base::Extended_filtration_data;
+  using Boundary_simplex_iterator = typename Base::Boundary_simplex_iterator;
 
  public:
 
@@ -188,6 +189,16 @@ class Simplex_tree_interface : public Simplex_tree<SimplexTreeOptions> {
     // this specific case works because the range is just a pair of iterators - won't work if range was a vector
     return Base::skeleton_simplex_range(dimension).end();
   }
+
+  Boundary_simplex_iterator get_boundary_iterator_begin(const Simplex& simplex) {
+    // this specific case works because the range is just a pair of iterators - won't work if range was a vector
+    return Base::boundary_simplex_range(Base::find(simplex)).begin();
+  }
+
+  Boundary_simplex_iterator get_boundary_iterator_end(const Simplex& simplex) {
+    // this specific case works because the range is just a pair of iterators - won't work if range was a vector
+    return Base::boundary_simplex_range(Base::find(simplex)).end();
+  }
 };
 
 }  // namespace Gudhi
diff --git a/src/python/test/test_simplex_tree.py b/src/python/test/test_simplex_tree.py
index 2137d822..7c49cb1a 100755
--- a/src/python/test/test_simplex_tree.py
+++ b/src/python/test/test_simplex_tree.py
@@ -340,3 +340,12 @@ def test_simplices_iterator():
         assert st.find(simplex[0]) == True
         print("filtration is: ", simplex[1])
         assert st.filtration(simplex[0]) == simplex[1]
+
+def test_boundaries_iterator():
+    st = SimplexTree()
+
+    assert st.insert([0, 1, 2, 3], filtration=1.0) == True
+    assert st.insert([1, 2, 3, 4], filtration=2.0) == True
+
+    assert list(st.get_boundaries([1, 2, 3])) == [([1, 2], 1.0), ([1, 3], 1.0), ([2, 3], 1.0)]
+    assert list(st.get_boundaries([2, 3, 4])) == [([2, 3], 1.0), ([2, 4], 2.0), ([3, 4], 2.0)]