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# Regina - A Normal Surface Theory Calculator
# Python Test Suite Component
#
# Copyright (c) 2007-2025, Ben Burton
# For further details contact Ben Burton (bab@debian.org).
#
# Tests different Euler characteristic calculations.
#
# This file is a single component of Regina's python test suite. To run
# the python test suite, move to the main python directory in the source
# tree and run "make check".
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation; either version 2 of the
# License, or (at your option) any later version.
#
# As an exception, when this program is distributed through (i) the
# App Store by Apple Inc.; (ii) the Mac App Store by Apple Inc.; or
# (iii) Google Play by Google Inc., then that store may impose any
# digital rights management, device limits and/or redistribution
# restrictions that are required by its terms of service.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
def printEuler(t, name):
print(t.eulerCharTri(), t.eulerCharManifold(), \
'---', name)
# Consistency check, while we're here.
eHom = regina.HomologicalData(t).eulerChar()
if eHom != t.eulerCharManifold():
print('ERROR: Triangulation3::eulerCharManifold() and')
print(' HomologicalData.eulerChar() disagree!')
print('Euler characteristics for triangulation vs compact manifold:')
# Empty:
printEuler(regina.Triangulation3(), "Empty triangulation")
# Closed:
printEuler(regina.Example3.lens(8,3), "L(8,3)")
printEuler(regina.Example3.rp2xs1(), "RP2 x S1")
# Bounded:
printEuler(regina.Example3.solidKleinBottle(),
"Solid Klein bottle")
printEuler(regina.Example3.lst(3,4), "LST(3,4,7)")
tri = regina.Triangulation3()
dummy = tri.newTetrahedron()
printEuler(tri, "Solid ball")
# Ideal:
printEuler(regina.Example3.figureEight(),
"Figure eight knot complement")
printEuler(regina.Example3.whiteheadLink(),
"Whitehead link complement")
printEuler(regina.Example3.gieseking(),
"Gieseking manifold")
printEuler(regina.Example3.cuspedGenusTwoTorus(),
"Cusped genus two torus")
# Edge joined to itself:
tri = regina.Triangulation3()
t = tri.newTetrahedron()
t.join(0, t, regina.Perm4(1,0,3,2))
t.join(2, t, regina.Perm4(1,0,3,2))
printEuler(tri, "Invalid edge")
# Subdivide to obtain a valid triangulation:
tri.subdivide()
printEuler(tri, "Two projective plane cusps")
# Invalid boundary vertex links:
tri = regina.Triangulation3()
(t, s) = tri.newTetrahedra(2)
t.join(3, s, regina.Perm4(0,1,2,3))
t.join(2, s, regina.Perm4(0,3,1,2))
printEuler(tri, "Pinched solid torus")
tri = regina.Triangulation3()
(t, s) = tri.newTetrahedra(2)
t.join(3, s, regina.Perm4(0,1,2,3))
t.join(2, s, regina.Perm4(0,2,1,3))
printEuler(tri, "Pinched solid Klein bottle")
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