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Trac #27429: some little code cleanup
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in two files, one about polyhedron, the other about toric varieties

various changes, for cleanness, speed or pep8

URL: https://trac.sagemath.org/27429
Reported by: chapoton
Ticket author(s): Frédéric Chapoton
Reviewer(s): Travis Scrimshaw
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@vbraun
Release Manager authored and vbraun committed Mar 5, 2019
2 parents 5b5d06a + 86fabb7 commit 063963f
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Showing 2 changed files with 40 additions and 54 deletions.
44 changes: 18 additions & 26 deletions src/sage/geometry/polyhedron/misc.py
View file
@@ -1,26 +1,19 @@
r"""
Miscellaneous helper functions
"""


########################################################################
# **********************************************************************
# Copyright (C) 2008 Marshall Hampton <hamptonio@gmail.com>
# Copyright (C) 2011 Volker Braun <vbraun.name@gmail.com>
#
# Distributed under the terms of the GNU General Public License (GPL)
#
# http://www.gnu.org/licenses/
########################################################################




# https://www.gnu.org/licenses/
# **********************************************************************


#########################################################################
def _to_space_separated_string(l):
"""
Converts a container to a space-separated string.
Convert a container to a space-separated string.
INPUT:
Expand All @@ -36,14 +29,9 @@ def _to_space_separated_string(l):
sage: P._to_space_separated_string([2,3])
'2 3'
"""
s = '';
for x in l:
if len(s)>0: s += ' '
s += repr(x)
return s
return ' '.join(repr(x) for x in l)


#########################################################################
def _set_to_None_if_empty(x):
"""
Helper function to clean up arguments: Returns None if x==None or
Expand All @@ -57,13 +45,14 @@ def _set_to_None_if_empty(x):
sage: P._set_to_None_if_empty([1])
[1]
"""
if x is None: return x
if x is None:
return x
x = list(x)
if len(x)==0: return None
if not x:
return None
return x


#########################################################################
def _make_listlist(x):
"""
Helper function to clean up arguments.
Expand All @@ -86,11 +75,11 @@ def _make_listlist(x):
sage: P._make_listlist([(1,2),[3,4]])
[[1, 2], [3, 4]]
"""
if x is None: return []
if x is None:
return []
return [list(y) for y in x]


#########################################################################
def _common_length_of(l1, l2=None, l3=None):
"""
The arguments are containers or ``None``. The function applies
Expand All @@ -107,10 +96,13 @@ def _common_length_of(l1, l2=None, l3=None):
sage: P._common_length_of([[1,2,3],[1,3,34]])
(2, 3)
"""
args = [];
if l1 is not None: args.append(l1)
if l2 is not None: args.append(l2)
if l3 is not None: args.append(l3)
args = []
if l1 is not None:
args.append(l1)
if l2 is not None:
args.append(l2)
if l3 is not None:
args.append(l3)

length = None
num = 0
Expand Down
50 changes: 22 additions & 28 deletions src/sage/schemes/toric/chow_group.py
View file
Expand Up @@ -69,7 +69,7 @@
(Z, C7, C2 x C2 x Z^5, Z)
sage: A.degree(2).ngens()
7
sage: a = sum( A.gen(i) * (i+1) for i in range(0,A.ngens()) ) # an element of A
sage: a = sum( A.gen(i) * (i+1) for i in range(A.ngens()) ) # an element of A
sage: a # long time (2s on sage.math, 2011)
( 3 | 1 mod 7 | 0 mod 2, 1 mod 2, 4, 5, 6, 7, 8 | 9 )
Expand Down Expand Up @@ -116,17 +116,17 @@
( 1 | 4 mod 7 | 1 mod 2, 1 mod 2, 1, 1, 1, 1, 1 | 1 )
sage: mixed.project_to_degree(1)
( 0 | 4 mod 7 | 0 mod 2, 0 mod 2, 0, 0, 0, 0, 0 | 0 )
sage: sum( mixed.project_to_degree(i) for i in range(0,X.dimension()+1) ) == mixed
sage: sum( mixed.project_to_degree(i) for i in range(X.dimension()+1) ) == mixed
True
"""

#*****************************************************************************
# ****************************************************************************
# Copyright (C) 2010 Volker Braun <vbraun.name@gmail.com>
#
# Distributed under the terms of the GNU General Public License (GPL)
#
# http://www.gnu.org/licenses/
#*****************************************************************************
# https://www.gnu.org/licenses/
# ****************************************************************************

from sage.misc.all import flatten
from sage.misc.fast_methods import WithEqualityById
Expand Down Expand Up @@ -193,7 +193,6 @@ def __init__(self, parent, v, check=True):
"""
FGP_Element.__init__(self, parent, v, check)


def _repr_(self):
r"""
Return a string representation of the Chow cycle.
Expand All @@ -217,30 +216,29 @@ def _repr_(self):
sage: A = X.Chow_group()
sage: A.degree()
(Z, 0, C2 x Z^5, Z)
sage: sum( A.gen(i) * (i+1) for i in range(0,A.ngens()) )
sage: sum( A.gen(i) * (i+1) for i in range(A.ngens()) )
( 2 || 1 mod 2, 3, 4, 5, 6, 7 | 8 )
"""
A = self.parent()
s = '('
for degree in range(0,A.scheme().dimension()+1):
if degree>0:
for degree in range(A.scheme().dimension() + 1):
if degree:
s += '|'
generators = A.gens(degree=degree)
coefficients = A.coordinate_vector(self, degree=degree)
if len(generators)>0:
if generators:
s += ' '
for i, gen in enumerate(generators):
if i>0:
if i > 0:
s += ', '
s += str(coefficients[i])
if gen.order() != Infinity:
s += ' mod '+str(gen.order())
if len(generators)>0:
s += ' mod ' + str(gen.order())
if generators:
s += ' '
s += ')'
return s


def degree(self):
r"""
The degree of the Chow cycle.
Expand Down Expand Up @@ -296,7 +294,7 @@ def project_to_degree(self, degree):
"""
ambient_dim = self.parent()._variety.dimension()
v = list(self.lift())
for i in range(0,len(v)):
for i in range(len(v)):
cone = self.parent()._cones[i]
if cone.dim() != ambient_dim-degree:
v[i] = 0
Expand Down Expand Up @@ -951,7 +949,7 @@ def degree(self, k=None):
pass

self._degree = tuple(ChowGroup_degree_class(self,d)
for d in range(0,self._variety.dimension()+1))
for d in range(self._variety.dimension() + 1))
return self._degree


Expand Down Expand Up @@ -1153,27 +1151,26 @@ def _repr_(self):
'Q'
"""
invariants = self._module.invariants()
if len(invariants)==0:
if not invariants:
return '0'

free = [x for x in invariants if x==0]
tors = [x for x in invariants if x> 0]
free = [x for x in invariants if x == 0]
tors = [x for x in invariants if x > 0]

if self._Chow_group.base_ring()==ZZ:
if self._Chow_group.base_ring() is ZZ:
ring = 'Z'
elif self._Chow_group.base_ring()==QQ:
elif self._Chow_group.base_ring() is QQ:
ring = 'Q'
else:
raise NotImplementedError('Base ring must be ZZ or QQ.')

s = ['C' + str(x) for x in tors]
if len(free)==1:
if len(free) == 1:
s.append(ring)
if len(free)>1:
elif len(free) > 1:
s.append(ring + '^' + str(len(free)))
return ' x '.join(s)


def module(self):
"""
Return the submodule of the toric Chow group generated.
Expand All @@ -1191,7 +1188,6 @@ def module(self):
"""
return self._module


def ngens(self):
"""
Return the number of generators.
Expand All @@ -1209,7 +1205,6 @@ def ngens(self):
"""
return len(self._gens)


def gen(self, i):
"""
Return the ``i``-th generator of the Chow group of fixed
Expand All @@ -1233,7 +1228,6 @@ def gen(self, i):
"""
return self._gens[i]


def gens(self):
"""
Return the generators of the Chow group of fixed degree.
Expand Down Expand Up @@ -1268,7 +1262,7 @@ def is_ChowGroup(x):
EXAMPLES::
sage: P2=toric_varieties.P2()
sage: P2 = toric_varieties.P2()
sage: A = P2.Chow_group()
sage: from sage.schemes.toric.chow_group import is_ChowGroup
sage: is_ChowGroup(A)
Expand Down

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