Initial revision
This commit is contained in:
Guido van Rossum
parent
12d12c5faf
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#
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# this is a rather strict implementation of a bit vector class
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# it is accessed the same way as an array of python-ints, except
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# the value must be 0 or 1
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#
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import sys; rprt = sys.stderr.write #for debugging
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error = 'bitvec.error'
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def _check_value(value):
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if type(value) != type(0) or not 0 <= value < 2:
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raise error, 'bitvec() items must have int value 0 or 1'
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import math
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def _compute_len(param):
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mant, l = math.frexp(float(param))
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bitmask = 1L << l
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if bitmask <= param:
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raise 'FATAL', '(param, l) = ' + `param, l`
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while l:
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bitmask = bitmask >> 1
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if param & bitmask:
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break
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l = l - 1
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return l
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def _check_key(len, key):
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if type(key) != type(0):
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raise TypeError, 'sequence subscript not int'
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if key < 0:
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key = key + len
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if not 0 <= key < len:
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raise IndexError, 'list index out of range'
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return key
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def _check_slice(len, i, j):
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#the type is ok, Python already checked that
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i, j = max(i, 0), min(len, j)
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if i > j:
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i = j
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return i, j
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class BitVec:
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def init(self, *params):
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self._data = 0L
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self._len = 0
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if not len(params):
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pass
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elif len(params) == 1:
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param, = params
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if type(param) == type([]):
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value = 0L
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bit_mask = 1L
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for item in param:
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# strict check
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#_check_value(item)
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if item:
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value = value | bit_mask
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bit_mask = bit_mask << 1
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self._data = value
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self._len = len(param)
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elif type(param) == type(0L):
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if param < 0:
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raise error, 'bitvec() can\'t handle negative longs'
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self._data = param
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self._len = _compute_len(param)
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else:
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raise error, 'bitvec() requires array or long parameter'
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elif len(params) == 2:
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param, length = params
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if type(param) == type(0L):
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if param < 0:
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raise error, \
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'can\'t handle negative longs'
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self._data = param
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if type(length) != type(0):
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raise error, 'bitvec()\'s 2nd parameter must be int'
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computed_length = _compute_len(param)
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if computed_length > length:
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print 'warning: bitvec() value is longer than the lenght indicates, truncating value'
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self._data = self._data & \
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((1L << length) - 1)
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self._len = length
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else:
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raise error, 'bitvec() requires array or long parameter'
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else:
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raise error, 'bitvec() requires 0 -- 2 parameter(s)'
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return self
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def _init(self, data, len):
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self._data = data
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self._len = len
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return self
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def append(self, item):
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#_check_value(item)
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#self[self._len:self._len] = [item]
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self[self._len:self._len] = \
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BitVec()._init(long(not not item), 1)
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def count(self, value):
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#_check_value(value)
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if value:
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data = self._data
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else:
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data = (~self)._data
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count = 0
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while data:
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data, count = data >> 1, count + (data & 1 != 0)
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return count
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def index(self, value):
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#_check_value(value):
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if value:
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data = self._data
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else:
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data = (~self)._data
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index = 0
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if not data:
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raise ValueError, 'list.index(x): x not in list'
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while not (data & 1):
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data, index = data >> 1, index + 1
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return index
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def insert(self, index, item):
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#_check_value(item)
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#self[index:index] = [item]
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self[index:index] = BitVec()._init(long(not not item), 1)
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def remove(self, value):
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del self[self.index(value)]
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def reverse(self):
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#ouch, this one is expensive!
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#for i in self._len>>1: self[i], self[l-i] = self[l-i], self[i]
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data, result = self._data, 0L
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for i in range(self._len):
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if not data:
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result = result << (self._len - i)
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break
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result, data = (result << 1) | (data & 1), data >> 1
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self._data = result
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def sort(self):
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c = self.count(1)
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self._data = ((1L << c) - 1) << (self._len - c)
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def copy(self):
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return BitVec()._init(self._data, self._len)
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def seq(self):
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result = []
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for i in self:
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result.append(i)
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return result
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def __repr__(self):
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##rprt('<bitvec class instance object>.' + '__repr__()\n')
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return 'bitvec' + `self._data, self._len`
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def __cmp__(self, other, *rest):
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#rprt(`self`+'.__cmp__'+`(other, ) + rest`+'\n')
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if type(other) != type(self):
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other = apply(bitvec, (other, ) + rest)
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#expensive solution... recursive binary, with slicing
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length = self._len
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if length == 0 or other._len == 0:
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return cmp(length, other._len)
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if length != other._len:
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min_lenght = min(length, other._len)
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return cmp(self[:min_length], other[:min_length]) or \
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cmp(self[min_length:], other[min_length:])
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#the lengths are the same now...
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if self._data == other._data:
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return 0
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if length == 1:
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return cmp(self[0], other[0])
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else:
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length = length >> 1
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return cmp(self[:length], other[:length]) or \
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cmp(self[length:], other[length:])
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def __len__(self):
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#rprt(`self`+'.__len__()\n')
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return self._len
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def __getitem__(self, key):
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#rprt(`self`+'.__getitem__('+`key`+')\n')
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key = _check_key(self._len, key)
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return self._data & (1L << key) != 0
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def __setitem__(self, key, value):
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#rprt(`self`+'.__setitem__'+`key, value`+'\n')
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key = _check_key(self._len, key)
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#_check_value(value)
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if value:
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self._data = self._data | (1L << key)
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else:
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self._data = self._data & ~(1L << key)
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def __delitem__(self, key):
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#rprt(`self`+'.__delitem__('+`key`+')\n')
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key = _check_key(self._len, key)
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#el cheapo solution...
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self._data = self[:key]._data | self[key+1:]._data >> key
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self._len = self._len - 1
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def __getslice__(self, i, j):
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#rprt(`self`+'.__getslice__'+`i, j`+'\n')
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i, j = _check_slice(self._len, i, j)
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if i >= j:
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return BitVec()._init(0L, 0)
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if i:
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ndata = self._data >> i
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else:
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ndata = self._data
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nlength = j - i
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if j != self._len:
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#we'll have to invent faster variants here
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#e.g. mod_2exp
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ndata = ndata & ((1L << nlength) - 1)
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return BitVec()._init(ndata, nlength)
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def __setslice__(self, i, j, sequence, *rest):
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#rprt(`self`+'.__setslice__'+`(i, j, sequence) + rest`+'\n')
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i, j = _check_slice(self._len, i, j)
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if type(sequence) != type(self):
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sequence = apply(bitvec, (sequence, ) + rest)
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#sequence is now of our own type
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ls_part = self[:i]
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ms_part = self[j:]
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self._data = ls_part._data | \
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((sequence._data | \
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(ms_part._data << sequence._len)) << ls_part._len)
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self._len = self._len - j + i + sequence._len
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def __delslice__(self, i, j):
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#rprt(`self`+'.__delslice__'+`i, j`+'\n')
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i, j = _check_slice(self._len, i, j)
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if i == 0 and j == self._len:
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self._data, self._len = 0L, 0
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elif i < j:
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self._data = self[:i]._data | (self[j:]._data >> i)
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self._len = self._len - j + i
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def __add__(self, other):
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#rprt(`self`+'.__add__('+`other`+')\n')
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retval = self.copy()
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retval[self._len:self._len] = other
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return retval
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def __mul__(self, multiplier):
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#rprt(`self`+'.__mul__('+`multiplier`+')\n')
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if type(multiplier) != type(0):
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raise TypeError, 'sequence subscript not int'
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if multiplier <= 0:
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return BitVec()._init(0L, 0)
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elif multiplier == 1:
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return self.copy()
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#handle special cases all 0 or all 1...
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if self._data == 0L:
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return BitVec()._init(0L, self._len * multiplier)
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elif (~self)._data == 0L:
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return ~BitVec()._init(0L, self._len * multiplier)
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#otherwise el cheapo again...
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retval = BitVec()._init(0L, 0)
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while multiplier:
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retval, multiplier = retval + self, multiplier - 1
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return retval
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def __and__(self, otherseq, *rest):
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#rprt(`self`+'.__and__'+`(otherseq, ) + rest`+'\n')
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if type(otherseq) != type(self):
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otherseq = apply(bitvec, (otherseq, ) + rest)
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#sequence is now of our own type
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return BitVec()._init(self._data & otherseq._data, \
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min(self._len, otherseq._len))
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def __xor__(self, otherseq, *rest):
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#rprt(`self`+'.__xor__'+`(otherseq, ) + rest`+'\n')
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if type(otherseq) != type(self):
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otherseq = apply(bitvec, (otherseq, ) + rest)
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#sequence is now of our own type
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return BitVec()._init(self._data ^ otherseq._data, \
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max(self._len, otherseq._len))
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def __or__(self, otherseq, *rest):
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#rprt(`self`+'.__or__'+`(otherseq, ) + rest`+'\n')
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if type(otherseq) != type(self):
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otherseq = apply(bitvec, (otherseq, ) + rest)
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#sequence is now of our own type
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return BitVec()._init(self._data | otherseq._data, \
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max(self._len, otherseq._len))
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def __invert__(self):
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#rprt(`self`+'.__invert__()\n')
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return BitVec()._init(~self._data & ((1L << self._len) - 1), \
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self._len)
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def __coerce__(self, otherseq, *rest):
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#needed for *some* of the arithmetic operations
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#rprt(`self`+'.__coerce__'+`(otherseq, ) + rest`+'\n')
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if type(otherseq) != type(self):
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otherseq = apply(bitvec, (otherseq, ) + rest)
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return self, otherseq
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def __int__(self):
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return int(self._data)
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def __long__(self):
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return long(self._data)
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def __float__(self):
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return float(self._data)
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def bitvec(params):
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return apply(BitVec().init, params)
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