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# Copyright (C) 2005 Canonical Ltd
#
# 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.
#
# 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, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
# Author: Martin Pool <mbp@canonical.com>
# Somewhat surprisingly, it turns out that this is much slower than
# simply storing the ints in a set() type. Python's performance model
# is very different to that of C.
class IntSet(Exception):
"""Faster set-like class storing only whole numbers.
Despite the name this stores long integers happily, but negative
values are not allowed.
>>> a = IntSet([0, 2, 5])
>>> bool(a)
True
>>> 2 in a
True
>>> 4 in a
False
>>> a.add(4)
>>> 4 in a
True
>>> b = IntSet()
>>> not b
True
>>> b.add(10)
>>> 10 in a
False
>>> a.update(b)
>>> 10 in a
True
>>> a.update(range(5))
>>> 3 in a
True
Being a set, duplicates are ignored:
>>> a = IntSet()
>>> a.add(10)
>>> a.add(10)
>>> 10 in a
True
>>> list(a)
[10]
"""
__slots__ = ['_val']
def __init__(self, values=None, bitmask=0L):
"""Create a new intset.
values
If specified, an initial collection of values.
"""
self._val = bitmask
if values is not None:
self.update(values)
def __nonzero__(self):
"""IntSets are false if empty, otherwise True.
>>> bool(IntSet())
False
>>> bool(IntSet([0]))
True
"""
return bool(self._val)
def __len__(self):
"""Number of elements in set.
>>> len(IntSet(xrange(20000)))
20000
"""
v = self._val
c = 0
while v:
if v & 1:
c += 1
v = v >> 1
return c
def __and__(self, other):
"""Set intersection.
>>> a = IntSet(range(10))
>>> len(a)
10
>>> b = a & a
>>> b == a
True
>>> a = a & IntSet([5, 7, 11, 13])
>>> list(a)
[5, 7]
"""
if not isinstance(other, IntSet):
raise NotImplementedError(type(other))
return IntSet(bitmask=(self._val & other._val))
def __or__(self, other):
"""Set union.
>>> a = IntSet(range(10)) | IntSet([5, 15, 25])
>>> len(a)
12
"""
if not isinstance(other, IntSet):
raise NotImplementedError(type(other))
return IntSet(bitmask=(self._val | other._val))
def __eq__(self, other):
"""Comparison.
>>> IntSet(range(3)) == IntSet([2, 0, 1])
True
"""
if isinstance(other, IntSet):
return self._val == other._val
else:
return False
def __ne__(self, other):
return not self.__eq__(other)
def __contains__(self, i):
return self._val & (1L << i)
def __iter__(self):
"""Return contents of set.
>>> list(IntSet())
[]
>>> list(IntSet([0, 1, 5, 7]))
[0, 1, 5, 7]
"""
v = self._val
o = 0
# XXX: This is a bit slow
while v:
if v & 1:
yield o
v = v >> 1
o = o + 1
def update(self, to_add):
"""Add all the values from the sequence or intset to_add"""
if isinstance(to_add, IntSet):
self._val |= to_add._val
else:
for i in to_add:
self._val |= (1L << i)
def add(self, to_add):
self._val |= (1L << to_add)
def remove(self, to_remove):
"""Remove one value from the set.
Raises KeyError if the value is not present.
>>> a = IntSet([10])
>>> a.remove(9)
Traceback (most recent call last):
File "/usr/lib/python2.4/doctest.py", line 1243, in __run
compileflags, 1) in test.globs
File "<doctest __main__.IntSet.remove[1]>", line 1, in ?
a.remove(9)
KeyError: 9
>>> a.remove(10)
>>> not a
True
"""
m = 1L << to_remove
if not self._val & m:
raise KeyError(to_remove)
self._val ^= m
def set_remove(self, to_remove):
"""Remove all values that exist in to_remove.
>>> a = IntSet(range(10))
>>> b = IntSet([2,3,4,7,12])
>>> a.set_remove(b)
>>> list(a)
[0, 1, 5, 6, 8, 9]
>>> a.set_remove([1,2,5])
>>> list(a)
[0, 6, 8, 9]
"""
if not isinstance(to_remove, IntSet):
self.set_remove(IntSet(to_remove))
return
intersect = self._val & to_remove._val
self._val ^= intersect
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