move cython in a gudhi directory - like the python package one

19 files changed, 128 insertions, 73 deletions

diff --git a/src/cython/CMakeLists.txt b/src/cython/CMakeLists.txt
index b69b2c7d..cd99f70b 100644
--- a/src/cython/CMakeLists.txt
+++ b/src/cython/CMakeLists.txt
@@ -195,7 +195,7 @@ if(PYTHONINTERP_FOUND)
 
     # Generate gudhi/__init__.py
     file(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/gudhi")
-    configure_file(__init__.py.in "${CMAKE_CURRENT_BINARY_DIR}/gudhi/__init__.py" @ONLY)
+    configure_file("gudhi/__init__.py.in" "${CMAKE_CURRENT_BINARY_DIR}/gudhi/__init__.py" @ONLY)
 
     add_custom_command(
         OUTPUT gudhi.so
diff --git a/src/cython/__init__.py.in b/src/cython/gudhi/__init__.py.in
index 60ad7865..60ad7865 100644
--- a/src/cython/__init__.py.in
+++ b/src/cython/gudhi/__init__.py.in
diff --git a/src/cython/cython/alpha_complex.pyx b/src/cython/gudhi/alpha_complex.pyx
index 249d51d0..85131780 100644
--- a/src/cython/cython/alpha_complex.pyx
+++ b/src/cython/gudhi/alpha_complex.pyx
@@ -3,8 +3,12 @@ from libcpp.vector cimport vector
 from libcpp.utility cimport pair
 from libcpp.string cimport string
 from libcpp cimport bool
+from libc.stdint cimport intptr_t
 import os
 
+from gudhi.simplex_tree cimport *
+from gudhi.simplex_tree import SimplexTree
+
 """ 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):       Vincent Rouvreau
@@ -104,6 +108,8 @@ cdef class AlphaComplex:
         :returns: A simplex tree created from the Delaunay Triangulation.
         :rtype: SimplexTree
         """
-        simplex_tree = SimplexTree()
-        self.thisptr.create_simplex_tree(simplex_tree.thisptr, max_alpha_square)
-        return simplex_tree
+        stree = SimplexTree()
+        cdef intptr_t stree_int_ptr=stree.thisptr
+        cdef Simplex_tree_interface_full_featured* stree_ptr = <Simplex_tree_interface_full_featured*>stree_int_ptr
+        self.thisptr.create_simplex_tree(stree_ptr, max_alpha_square)
+        return stree
diff --git a/src/cython/cython/bottleneck_distance.pyx b/src/cython/gudhi/bottleneck_distance.pyx
index 4b378cbc..4b378cbc 100644
--- a/src/cython/cython/bottleneck_distance.pyx
+++ b/src/cython/gudhi/bottleneck_distance.pyx
diff --git a/src/cython/cython/cubical_complex.pyx b/src/cython/gudhi/cubical_complex.pyx
index 0dc133d1..0dc133d1 100644
--- a/src/cython/cython/cubical_complex.pyx
+++ b/src/cython/gudhi/cubical_complex.pyx
diff --git a/src/cython/cython/euclidean_strong_witness_complex.pyx b/src/cython/gudhi/euclidean_strong_witness_complex.pyx
index 26bd8375..26bd8375 100644
--- a/src/cython/cython/euclidean_strong_witness_complex.pyx
+++ b/src/cython/gudhi/euclidean_strong_witness_complex.pyx
diff --git a/src/cython/cython/euclidean_witness_complex.pyx b/src/cython/gudhi/euclidean_witness_complex.pyx
index e687c6f3..e687c6f3 100644
--- a/src/cython/cython/euclidean_witness_complex.pyx
+++ b/src/cython/gudhi/euclidean_witness_complex.pyx
diff --git a/src/cython/cython/nerve_gic.pyx b/src/cython/gudhi/nerve_gic.pyx
index 3c8f1200..3c8f1200 100644
--- a/src/cython/cython/nerve_gic.pyx
+++ b/src/cython/gudhi/nerve_gic.pyx
diff --git a/src/cython/cython/off_reader.pyx b/src/cython/gudhi/off_reader.pyx
index 9efd97ff..9efd97ff 100644
--- a/src/cython/cython/off_reader.pyx
+++ b/src/cython/gudhi/off_reader.pyx
diff --git a/src/cython/cython/periodic_cubical_complex.pyx b/src/cython/gudhi/periodic_cubical_complex.pyx
index 724fadd4..724fadd4 100644
--- a/src/cython/cython/periodic_cubical_complex.pyx
+++ b/src/cython/gudhi/periodic_cubical_complex.pyx
diff --git a/src/cython/cython/persistence_graphical_tools.py b/src/cython/gudhi/persistence_graphical_tools.py
index 34803222..34803222 100644
--- a/src/cython/cython/persistence_graphical_tools.py
+++ b/src/cython/gudhi/persistence_graphical_tools.py
diff --git a/src/cython/cython/reader_utils.pyx b/src/cython/gudhi/reader_utils.pyx
index 147fae71..147fae71 100644
--- a/src/cython/cython/reader_utils.pyx
+++ b/src/cython/gudhi/reader_utils.pyx
diff --git a/src/cython/cython/rips_complex.pyx b/src/cython/gudhi/rips_complex.pyx
index b9a2331f..1a6c8571 100644
--- a/src/cython/cython/rips_complex.pyx
+++ b/src/cython/gudhi/rips_complex.pyx
@@ -3,7 +3,10 @@ from libcpp.vector cimport vector
 from libcpp.utility cimport pair
 from libcpp.string cimport string
 from libcpp cimport bool
-import os
+from libc.stdint cimport intptr_t
+
+from gudhi.simplex_tree cimport *
+from gudhi.simplex_tree import SimplexTree
 
 """ 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.
@@ -93,6 +96,7 @@ cdef class RipsComplex:
         :returns: A simplex tree created from the Delaunay Triangulation.
         :rtype: SimplexTree
         """
-        simplex_tree = SimplexTree()
-        self.thisref.create_simplex_tree(simplex_tree.thisptr, max_dimension)
-        return simplex_tree
+        stree = SimplexTree()
+        cdef intptr_t stree_ptr=stree.thisptr
+        self.thisref.create_simplex_tree(<Simplex_tree_interface_full_featured*>stree_ptr, max_dimension)
+        return stree
diff --git a/src/cython/gudhi/simplex_tree.pxd b/src/cython/gudhi/simplex_tree.pxd
new file mode 100644
index 00000000..25051295
--- /dev/null
+++ b/src/cython/gudhi/simplex_tree.pxd
@@ -0,0 +1,46 @@
+from cython cimport numeric
+from libcpp.vector cimport vector
+from libcpp.utility cimport pair
+from libcpp cimport bool
+from libcpp.string cimport string
+
+""" 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):       Vincent Rouvreau
+
+    Copyright (C) 2016 Inria
+
+    Modification(s):
+      - YYYY/MM Author: Description of the modification
+"""
+
+__author__ = "Vincent Rouvreau"
+__copyright__ = "Copyright (C) 2016 Inria"
+__license__ = "MIT"
+
+cdef extern from "Simplex_tree_interface.h" namespace "Gudhi":
+    cdef cppclass Simplex_tree_options_full_featured:
+        pass
+
+    cdef cppclass Simplex_tree_interface_full_featured "Gudhi::Simplex_tree_interface<Gudhi::Simplex_tree_options_full_featured>":
+        Simplex_tree()
+        double simplex_filtration(vector[int] simplex)
+        void assign_simplex_filtration(vector[int] simplex, double filtration)
+        void initialize_filtration()
+        int num_vertices()
+        int num_simplices()
+        void set_dimension(int dimension)
+        int dimension()
+        int upper_bound_dimension()
+        bool find_simplex(vector[int] simplex)
+        bool insert_simplex_and_subfaces(vector[int] simplex,
+                                         double filtration)
+        vector[pair[vector[int], double]] get_filtration()
+        vector[pair[vector[int], double]] get_skeleton(int dimension)
+        vector[pair[vector[int], double]] get_star(vector[int] simplex)
+        vector[pair[vector[int], double]] get_cofaces(vector[int] simplex,
+                                                          int dimension)
+        void expansion(int max_dim)
+        void remove_maximal_simplex(vector[int] simplex)
+        bool prune_above_filtration(double filtration)
+        bool make_filtration_non_decreasing()
diff --git a/src/cython/cython/simplex_tree.pyx b/src/cython/gudhi/simplex_tree.pyx
index 8e791c17..e5f9e9d1 100644
--- a/src/cython/cython/simplex_tree.pyx
+++ b/src/cython/gudhi/simplex_tree.pyx
@@ -1,9 +1,4 @@
-from cython cimport numeric
-from libcpp.vector cimport vector
-from libcpp.utility cimport pair
-from libcpp cimport bool
-from libcpp.string cimport string
-
+from libc.stdint cimport intptr_t
 from numpy import array as np_array
 
 """ This file is part of the Gudhi Library - https://gudhi.inria.fr/ - which is released under MIT.
@@ -20,33 +15,6 @@ __author__ = "Vincent Rouvreau"
 __copyright__ = "Copyright (C) 2016 Inria"
 __license__ = "MIT"
 
-cdef extern from "Simplex_tree_interface.h" namespace "Gudhi":
-    cdef cppclass Simplex_tree_options_full_featured:
-        pass
-
-    cdef cppclass Simplex_tree_interface_full_featured "Gudhi::Simplex_tree_interface<Gudhi::Simplex_tree_options_full_featured>":
-        Simplex_tree()
-        double simplex_filtration(vector[int] simplex)
-        void assign_simplex_filtration(vector[int] simplex, double filtration)
-        void initialize_filtration()
-        int num_vertices()
-        int num_simplices()
-        void set_dimension(int dimension)
-        int dimension()
-        int upper_bound_dimension()
-        bool find_simplex(vector[int] simplex)
-        bool insert_simplex_and_subfaces(vector[int] simplex,
-                                         double filtration)
-        vector[pair[vector[int], double]] get_filtration()
-        vector[pair[vector[int], double]] get_skeleton(int dimension)
-        vector[pair[vector[int], double]] get_star(vector[int] simplex)
-        vector[pair[vector[int], double]] get_cofaces(vector[int] simplex,
-                                                          int dimension)
-        void expansion(int max_dim)
-        void remove_maximal_simplex(vector[int] simplex)
-        bool prune_above_filtration(double filtration)
-        bool make_filtration_non_decreasing()
-
 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>>":
         Simplex_tree_persistence_interface(Simplex_tree_interface_full_featured * st, bool persistence_dim_max)
@@ -68,7 +36,13 @@ cdef class SimplexTree:
     This class is a filtered, with keys, and non contiguous vertices version
     of the simplex tree.
     """
-    cdef Simplex_tree_interface_full_featured * thisptr
+    # unfortunately 'cdef public Simplex_tree_interface_full_featured* thisptr' is not possible
+    # Use intptr_t instead to cast the pointer
+    cdef public intptr_t thisptr
+
+    # Get the pointer casted as it should be
+    cdef Simplex_tree_interface_full_featured* get_ptr(self):
+        return <Simplex_tree_interface_full_featured*>(self.thisptr)
 
     cdef Simplex_tree_persistence_interface * pcohptr
 
@@ -79,18 +53,20 @@ cdef class SimplexTree:
 
     # The real cython constructor
     def __cinit__(self):
-        self.thisptr = new Simplex_tree_interface_full_featured()
+        cdef Simplex_tree_interface_full_featured* ptr = new Simplex_tree_interface_full_featured()
+        self.thisptr = <intptr_t>ptr
 
     def __dealloc__(self):
-        if self.thisptr != NULL:
-            del self.thisptr
+        cdef Simplex_tree_interface_full_featured* ptr = self.get_ptr()
+        if ptr != NULL:
+            del ptr
         if self.pcohptr != NULL:
             del self.pcohptr
 
     def __is_defined(self):
         """Returns true if SimplexTree pointer is not NULL.
          """
-        return self.thisptr != NULL
+        return self.get_ptr() != NULL
 
     def __is_persistence_defined(self):
         """Returns true if Persistence pointer is not NULL.
@@ -106,7 +82,7 @@ cdef class SimplexTree:
         :returns:  The simplicial complex filtration value.
         :rtype:  float
         """
-        return self.thisptr.simplex_filtration(simplex)
+        return self.get_ptr().simplex_filtration(simplex)
 
     def assign_filtration(self, simplex, filtration):
         """This function assigns the simplicial complex filtration value for a
@@ -117,7 +93,7 @@ cdef class SimplexTree:
         :param filtration:  The simplicial complex filtration value.
         :type filtration:  float
         """
-        self.thisptr.assign_simplex_filtration(simplex, filtration)
+        self.get_ptr().assign_simplex_filtration(simplex, filtration)
 
     def initialize_filtration(self):
         """This function initializes and sorts the simplicial complex
@@ -134,7 +110,7 @@ cdef class SimplexTree:
             :func:`removing<gudhi.SimplexTree.remove_maximal_simplex>`
             simplices.
         """
-        self.thisptr.initialize_filtration()
+        self.get_ptr().initialize_filtration()
 
     def num_vertices(self):
         """This function returns the number of vertices of the simplicial
@@ -143,7 +119,7 @@ cdef class SimplexTree:
         :returns:  The simplicial complex number of vertices.
         :rtype:  int
         """
-        return self.thisptr.num_vertices()
+        return self.get_ptr().num_vertices()
 
     def num_simplices(self):
         """This function returns the number of simplices of the simplicial
@@ -152,7 +128,7 @@ cdef class SimplexTree:
         :returns:  the simplicial complex number of simplices.
         :rtype:  int
         """
-        return self.thisptr.num_simplices()
+        return self.get_ptr().num_simplices()
 
     def dimension(self):
         """This function returns the dimension of the simplicial complex.
@@ -169,7 +145,7 @@ cdef class SimplexTree:
             :func:`prune_above_filtration()<gudhi.SimplexTree.prune_above_filtration>`
             methods).
         """
-        return self.thisptr.dimension()
+        return self.get_ptr().dimension()
 
     def upper_bound_dimension(self):
         """This function returns a valid dimension upper bound of the
@@ -178,7 +154,7 @@ cdef class SimplexTree:
         :returns:  an upper bound on the dimension of the simplicial complex.
         :rtype:  int
         """
-        return self.thisptr.upper_bound_dimension()
+        return self.get_ptr().upper_bound_dimension()
 
     def set_dimension(self, dimension):
         """This function sets the dimension of the simplicial complex.
@@ -196,7 +172,7 @@ cdef class SimplexTree:
             :func:`prune_above_filtration()<gudhi.SimplexTree.prune_above_filtration>`
             ).
         """
-        self.thisptr.set_dimension(<int>dimension)
+        self.get_ptr().set_dimension(<int>dimension)
 
     def find(self, simplex):
         """This function returns if the N-simplex was found in the simplicial
@@ -210,7 +186,7 @@ cdef class SimplexTree:
         cdef vector[int] csimplex
         for i in simplex:
             csimplex.push_back(i)
-        return self.thisptr.find_simplex(csimplex)
+        return self.get_ptr().find_simplex(csimplex)
 
     def insert(self, simplex, filtration=0.0):
         """This function inserts the given N-simplex and its subfaces with the
@@ -230,7 +206,7 @@ cdef class SimplexTree:
         cdef vector[int] csimplex
         for i in simplex:
             csimplex.push_back(i)
-        return self.thisptr.insert_simplex_and_subfaces(csimplex,
+        return self.get_ptr().insert_simplex_and_subfaces(csimplex,
                                                         <double>filtration)
 
     def get_filtration(self):
@@ -241,7 +217,7 @@ cdef class SimplexTree:
         :rtype:  list of tuples(simplex, filtration)
         """
         cdef vector[pair[vector[int], double]] filtration \
-            = self.thisptr.get_filtration()
+            = self.get_ptr().get_filtration()
         ct = []
         for filtered_complex in filtration:
             v = []
@@ -260,7 +236,7 @@ cdef class SimplexTree:
         :rtype:  list of tuples(simplex, filtration)
         """
         cdef vector[pair[vector[int], double]] skeleton \
-            = self.thisptr.get_skeleton(<int>dimension)
+            = self.get_ptr().get_skeleton(<int>dimension)
         ct = []
         for filtered_simplex in skeleton:
             v = []
@@ -281,7 +257,7 @@ cdef class SimplexTree:
         for i in simplex:
             csimplex.push_back(i)
         cdef vector[pair[vector[int], double]] star \
-            = self.thisptr.get_star(csimplex)
+            = self.get_ptr().get_star(csimplex)
         ct = []
         for filtered_simplex in star:
             v = []
@@ -306,7 +282,7 @@ cdef class SimplexTree:
         for i in simplex:
             csimplex.push_back(i)
         cdef vector[pair[vector[int], double]] cofaces \
-            = self.thisptr.get_cofaces(csimplex, <int>codimension)
+            = self.get_ptr().get_cofaces(csimplex, <int>codimension)
         ct = []
         for filtered_simplex in cofaces:
             v = []
@@ -337,7 +313,7 @@ cdef class SimplexTree:
             :func:`dimension()<gudhi.SimplexTree.dimension>`
             to recompute the exact dimension.
         """
-        self.thisptr.remove_maximal_simplex(simplex)
+        self.get_ptr().remove_maximal_simplex(simplex)
 
     def prune_above_filtration(self, filtration):
         """Prune above filtration value given as parameter.
@@ -370,7 +346,7 @@ cdef class SimplexTree:
             :func:`dimension()<gudhi.SimplexTree.dimension>`
             method to recompute the exact dimension.
         """
-        return self.thisptr.prune_above_filtration(filtration)
+        return self.get_ptr().prune_above_filtration(filtration)
 
     def expansion(self, max_dim):
         """Expands the Simplex_tree containing only its one skeleton
@@ -389,7 +365,7 @@ cdef class SimplexTree:
         :param max_dim: The maximal dimension.
         :type max_dim: int.
         """
-        self.thisptr.expansion(max_dim)
+        self.get_ptr().expansion(max_dim)
 
     def make_filtration_non_decreasing(self):
         """This function ensures that each simplex has a higher filtration
@@ -410,7 +386,7 @@ cdef class SimplexTree:
             :func:`initialize_filtration()<gudhi.SimplexTree.initialize_filtration>`
             to recompute it.
         """
-        return self.thisptr.make_filtration_non_decreasing()
+        return self.get_ptr().make_filtration_non_decreasing()
 
     def persistence(self, homology_coeff_field=11, min_persistence=0, persistence_dim_max = False):
         """This function returns the persistence of the simplicial complex.
@@ -432,7 +408,7 @@ cdef class SimplexTree:
         """
         if self.pcohptr != NULL:
             del self.pcohptr
-        self.pcohptr = new Simplex_tree_persistence_interface(self.thisptr, persistence_dim_max)
+        self.pcohptr = new Simplex_tree_persistence_interface(self.get_ptr(), persistence_dim_max)
         cdef vector[pair[int, pair[double, double]]] persistence_result
         if self.pcohptr != NULL:
             persistence_result = self.pcohptr.get_persistence(homology_coeff_field, min_persistence)
diff --git a/src/cython/cython/strong_witness_complex.pyx b/src/cython/gudhi/strong_witness_complex.pyx
index 8c155815..4e3d1b67 100644
--- a/src/cython/cython/strong_witness_complex.pyx
+++ b/src/cython/gudhi/strong_witness_complex.pyx
@@ -1,6 +1,10 @@
 from cython cimport numeric
 from libcpp.vector cimport vector
 from libcpp.utility cimport pair
+from libc.stdint cimport intptr_t
+
+from gudhi.simplex_tree cimport *
+from gudhi.simplex_tree import SimplexTree
 
 """ 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.
@@ -63,9 +67,12 @@ cdef class StrongWitnessComplex:
         :returns: A simplex tree created from the Delaunay Triangulation.
         :rtype: SimplexTree
         """
-        simplex_tree = SimplexTree()
+        stree = SimplexTree()
+        cdef intptr_t stree_int_ptr=stree.thisptr
+        cdef Simplex_tree_interface_full_featured* stree_ptr = <Simplex_tree_interface_full_featured*>stree_int_ptr
         if limit_dimension is not -1:
-            self.thisptr.create_simplex_tree(simplex_tree.thisptr, max_alpha_square, limit_dimension)
+            self.thisptr.create_simplex_tree(stree_ptr,
+                max_alpha_square, limit_dimension)
         else:
-            self.thisptr.create_simplex_tree(simplex_tree.thisptr, max_alpha_square)
-        return simplex_tree
+            self.thisptr.create_simplex_tree(stree_ptr, max_alpha_square)
+        return stree
diff --git a/src/cython/cython/subsampling.pyx b/src/cython/gudhi/subsampling.pyx
index 1135c1fb..1135c1fb 100644
--- a/src/cython/cython/subsampling.pyx
+++ b/src/cython/gudhi/subsampling.pyx
diff --git a/src/cython/cython/tangential_complex.pyx b/src/cython/gudhi/tangential_complex.pyx
index 00a84810..b2d55520 100644
--- a/src/cython/cython/tangential_complex.pyx
+++ b/src/cython/gudhi/tangential_complex.pyx
@@ -3,8 +3,12 @@ from libcpp.vector cimport vector
 from libcpp.utility cimport pair
 from libcpp.string cimport string
 from libcpp cimport bool
+from libc.stdint cimport intptr_t
 import os
 
+from gudhi.simplex_tree cimport *
+from gudhi.simplex_tree import SimplexTree
+
 """ 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):       Vincent Rouvreau
@@ -138,6 +142,11 @@ cdef class TangentialComplex:
         :returns: A simplex tree created from the complex.
         :rtype: SimplexTree
         """
+        stree = SimplexTree()
+        cdef intptr_t stree_int_ptr=stree.thisptr
+        cdef Simplex_tree_interface_full_featured* stree_ptr = <Simplex_tree_interface_full_featured*>stree_int_ptr
+        self.thisptr.create_simplex_tree(stree_ptr)
+        return stree
         simplex_tree = SimplexTree()
         self.thisptr.create_simplex_tree(simplex_tree.thisptr)
         return simplex_tree
diff --git a/src/cython/cython/witness_complex.pyx b/src/cython/gudhi/witness_complex.pyx
index 91046f57..c859877d 100644
--- a/src/cython/cython/witness_complex.pyx
+++ b/src/cython/gudhi/witness_complex.pyx
@@ -1,6 +1,10 @@
 from cython cimport numeric
 from libcpp.vector cimport vector
 from libcpp.utility cimport pair
+from libc.stdint cimport intptr_t
+
+from gudhi.simplex_tree cimport *
+from gudhi.simplex_tree import SimplexTree
 
 """ 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.
@@ -63,9 +67,12 @@ cdef class WitnessComplex:
         :returns: A simplex tree created from the Delaunay Triangulation.
         :rtype: SimplexTree
         """
-        simplex_tree = SimplexTree()
+        stree = SimplexTree()
+        cdef intptr_t stree_int_ptr=stree.thisptr
+        cdef Simplex_tree_interface_full_featured* stree_ptr = <Simplex_tree_interface_full_featured*>stree_int_ptr
         if limit_dimension is not -1:
-            self.thisptr.create_simplex_tree(simplex_tree.thisptr, max_alpha_square, limit_dimension)
+            self.thisptr.create_simplex_tree(stree_ptr,
+                max_alpha_square, limit_dimension)
         else:
-            self.thisptr.create_simplex_tree(simplex_tree.thisptr, max_alpha_square)
-        return simplex_tree
+            self.thisptr.create_simplex_tree(stree_ptr, max_alpha_square)
+        return stree