def iterate_binary(self, k):
"""
This is a helper function. It iterates over the
binary subsets by k steps. This variable can be
both positive or negative.
Examples
========
>>> from sympy.combinatorics.subsets import Subset
>>> a = Subset(['c','d'], ['a','b','c','d'])
>>> a.iterate_binary(-2).subset
['d']
>>> a = Subset(['a','b','c'], ['a','b','c','d'])
>>> a.iterate_binary(2).subset
[]
See Also
========
next_binary, prev_binary
"""
bin_list = Subset.bitlist_from_subset(self.subset, self.superset)
n = (int(''.join(bin_list), 2) + k) % 2**self.superset_size
bits = bin(n)[2:].rjust(self.superset_size, '0')
return Subset.subset_from_bitlist(self.superset, bits)
def iterate_binary(self, k):
"""
This is a helper function. It iterates over the
binary subsets by k steps. This variable can be
both positive or negative.
Examples
========
>>> from sympy.combinatorics.subsets import Subset
>>> a = Subset(['c','d'], ['a','b','c','d'])
>>> a.iterate_binary(-2).subset
['d']
>>> a = Subset(['a','b','c'], ['a','b','c','d'])
>>> a.iterate_binary(2).subset
[]
See Also
========
next_binary, prev_binary
"""
bin_list = Subset.bitlist_from_subset(self.subset, self.superset)
next_bin_list = list(bin((int(reduce(lambda x, y:
x + y, bin_list), 2) + k)
% 2**self.superset_size))[2:]
next_bin_list = [0] * (self.superset_size - len(next_bin_list)) + \
next_bin_list
return Subset.subset_from_bitlist(self.superset, next_bin_list)
def iterate_binary(self, k):
"""
This is a helper function. It iterates over the
binary subsets by k steps. This variable can be
both positive or negative.
Examples
========
>>> from sympy.combinatorics.subsets import Subset
>>> a = Subset(['c','d'], ['a','b','c','d'])
>>> a.iterate_binary(-2).subset
['d']
>>> a = Subset(['a','b','c'], ['a','b','c','d'])
>>> a.iterate_binary(2).subset
[]
See Also
========
next_binary, prev_binary
"""
bin_list = Subset.bitlist_from_subset(self.subset, self.superset)
next_bin_list = list(
bin((int(reduce(lambda x, y: x + y, bin_list), 2) + k) %
2**self.superset_size))[2:]
next_bin_list = [0] * (self.superset_size - len(next_bin_list)) + \
next_bin_list
return Subset.subset_from_bitlist(self.superset, next_bin_list)
def current(self):
"""
Returns the currently referenced Gray code as a bit string.
>>> from sympy.combinatorics.graycode import GrayCode
>>> GrayCode(3, start='100').current
'100'
"""
rv = self._current or '0'
if type(rv) is not str:
rv = bin(rv)[2:]
return rv.rjust(self.n, '0')
def unrank_binary(self, rank, superset):
"""
Gets the binary ordered subset of the specified rank.
Examples:
>>> from sympy.combinatorics.subsets import Subset
>>> Subset.unrank_binary(4, ['a','b','c','d']).subset
['b']
"""
bin_list = list(bin(rank))[2:]
bin_list = [0] * (len(superset) - len(bin_list)) + bin_list
return Subset.subset_from_bitlist(superset, bin_list)
def unrank_binary(self, rank, superset):
"""
Gets the binary ordered subset of the specified rank.
Examples
========
>>> from sympy.combinatorics.subsets import Subset
>>> Subset.unrank_binary(4, ['a','b','c','d']).subset
['b']
"""
bin_list = list(bin(rank))[2:]
bin_list = [0] * (len(superset) - len(bin_list)) + bin_list
return Subset.subset_from_bitlist(superset, bin_list)
def POSform(variables, minterms, dontcares=[]):
"""
The POSform function uses simplified_pairs and a redundant-group
eliminating algorithm to convert the list of all input combinations
that generate '1' (the minterms) into the smallest Product of Sums form.
The variables must be given as the first argument.
Return a logical And function (i.e., the "product of sums" or "POS"
form) that gives the desired outcome. If there are inputs that can
be ignored, pass them as a list too.
The result will be one of the (perhaps many) functions that satisfy
the conditions.
Examples
========
>>> from sympy.logic import POSform
>>> minterms = [[0, 0, 0, 1], [0, 0, 1, 1], [0, 1, 1, 1],
... [1, 0, 1, 1], [1, 1, 1, 1]]
>>> dontcares = [[0, 0, 0, 0], [0, 0, 1, 0], [0, 1, 0, 1]]
>>> POSform(['w','x','y','z'], minterms, dontcares)
And(Or(Not(w), y), z)
References
==========
.. [1] en.wikipedia.org/wiki/Quine-McCluskey_algorithm
"""
variables = [str(v) for v in variables]
from sympy.core.compatibility import bin
if minterms == []:
return False
t = [0] * len(variables)
maxterms = []
for x in range(2 ** len(variables)):
b = [int(y) for y in bin(x)[2:]]
t[-len(b):] = b
if (t not in minterms) and (t not in dontcares):
maxterms.append(t[:])
l2 = [1]
l1 = maxterms + dontcares
while (l1 != l2):
l1 = _simplified_pairs(l1)
l2 = _simplified_pairs(l1)
string = _rem_redundancy(l1, maxterms, variables, 2)
if string == '':
return True
return sympify(string)
def current(self):
"""
Returns the currently referenced Gray code as a bit string.
Examples
========
>>> from sympy.combinatorics.graycode import GrayCode
>>> GrayCode(3, start='100').current
'100'
"""
rv = self._current or '0'
if type(rv) is not str:
rv = bin(rv)[2:]
return rv.rjust(self.n, '0')
def arr(num, t):
"""Return a list of ``t`` binary digits of ``num``; low digits rightmost.
Examples
========
>>> from sympy.physics.quantum.shor import arr
>>> arr(5, 6)
[0, 0, 0, 1, 0, 1]
>>> arr(5, 2)
[0, 1]
"""
binary_array = [0]*t
b = list(bin(abs(num))[2:]) # strip 0b
b = b[-t:]
for i in range(-1, -min(len(b), t) - 1, -1):
binary_array[i] = int(b[i])
return binary_array
def arr(num, t):
"""Return a list of ``t`` binary digits of ``num``; low digits rightmost.
Examples
========
>>> from sympy.physics.quantum.shor import arr
>>> arr(5, 6)
[0, 0, 0, 1, 0, 1]
>>> arr(5, 2)
[0, 1]
"""
binary_array = [0] * t
b = list(bin(abs(num))[2:]) # strip 0b
b = b[-t:]
for i in range(-1, -min(len(b), t) - 1, -1):
binary_array[i] = int(b[i])
return binary_array
def unrank_binary(self, rank, superset):
"""
Gets the binary ordered subset of the specified rank.
Examples
========
>>> from sympy.combinatorics.subsets import Subset
>>> Subset.unrank_binary(4, ['a','b','c','d']).subset
['b']
See Also
========
iterate_binary, rank_binary
"""
bits = bin(rank)[2:].rjust(len(superset), '0')
return Subset.subset_from_bitlist(superset, bits)
def simplify_logic(expr):
"""
This function simplifies a boolean function to its
simplified version in SOP or POS form. The return type is a
Or object or And object in SymPy. The input can be a string
or a boolean expression.
Examples
========
>>> from sympy.logic import simplify_logic
>>> from sympy.abc import x, y, z
>>> from sympy import S
>>> b = '(~x & ~y & ~z) | ( ~x & ~y & z)'
>>> simplify_logic(b)
And(Not(x), Not(y))
>>> S(b)
Or(And(Not(x), Not(y), Not(z)), And(Not(x), Not(y), z))
>>> simplify_logic(_)
And(Not(x), Not(y))
"""
from sympy.core.compatibility import bin
expr = sympify(expr)
variables = list(expr.free_symbols)
string_variables = [x.name for x in variables]
truthtable = []
t = [0] * len(variables)
for x in range(2 ** len(variables)):
b = [int(y) for y in bin(x)[2:]]
t[-len(b):] = b
if expr.subs(zip(variables, [bool(i) for i in t])) is True:
truthtable.append(t[:])
if (len(truthtable) >= (2 ** (len(variables) - 1))):
return SOPform(string_variables, truthtable)
else:
return POSform(string_variables, truthtable)
