def logically_reduce(self, token_list):
"""Return token_list in conjunctive normal form as a string.
CNF has the property that there will only ever be one level of
parenthetical nesting, and all distributable operators (such as
the not in -(p | q) will be fully distributed (as -p + -q).
"""
maxdepth, dummy_balanced, d0_p = self.nesting_depth_and_balance(
token_list)
s = ' '.join(token_list)
s = self._invenio_to_python_logical(s)
last_maxdepth = 0
while maxdepth != last_maxdepth: # XXX: sometimes NaryExpr doesn't
try: # fully flatten Expr; but it usually
s = str(to_cnf(s)) # does in 2 passes FIXME: diagnose
except SyntaxError:
raise SyntaxError(
str(s) + " couldn't be converted to a logic expression.")
last_maxdepth = maxdepth
maxdepth, dummy_balanced, d0_p = self.nesting_depth_and_balance(
self.tokenize(s))
if d0_p == 1 and s[0] == '(' and s[
-1] == ')': # s can come back with extra parens
s = s[1:-1]
s = self._python_logical_to_invenio(s)
return s
def logically_reduce(self, token_list):
"""Return token_list in conjunctive normal form as a string.
CNF has the property that there will only ever be one level of
parenthetical nesting, and all distributable operators (such as
the not in -(p | q) will be fully distributed (as -p + -q).
"""
maxdepth, dummy_balanced, d0_p = self.nesting_depth_and_balance(token_list)
s = " ".join(token_list)
s = self._invenio_to_python_logical(s)
last_maxdepth = 0
while maxdepth != last_maxdepth: # XXX: sometimes NaryExpr doesn't
try: # fully flatten Expr; but it usually
s = str(to_cnf(s)) # does in 2 passes FIXME: diagnose
except SyntaxError:
raise SyntaxError(str(s) + " couldn't be converted to a logic expression.")
last_maxdepth = maxdepth
maxdepth, dummy_balanced, d0_p = self.nesting_depth_and_balance(self.tokenize(s))
if d0_p == 1 and s[0] == "(" and s[-1] == ")": # s can come back with extra parens
s = s[1:-1]
s = self._python_logical_to_invenio(s)
return s
def test_ANDed_pair(self):
"""logicutils - ANDed pair should be in CNF"""
self.assertEqual(to_cnf(expr('a & b')),
Expr('&', 'a', 'b'))
def test_ORed_pair(self):
"""logicutils - ORed pair should be in CNF"""
self.assertEqual(to_cnf(expr('a | b')),
Expr('|', 'a', 'b'))
def test_complex_example_Norvig(self):
"""logicutils - (P&Q) | (~P & ~Q) in CNF"""
self.assertEqual(str(to_cnf('(P&Q) | (~P & ~Q)')),
str('((~P | P) & (~Q | P) & (~P | Q) & (~Q | Q))'))
def test_singleton(self):
"""logicutils - singletons are already in CNF"""
self.assertEqual(to_cnf(expr('a')),
Expr('a'))
def test_ANDed_pair(self):
"""logicutils - ANDed pair should be in CNF"""
self.assertEqual(to_cnf(expr('a & b')), Expr('&', 'a', 'b'))
def test_ORed_pair(self):
"""logicutils - ORed pair should be in CNF"""
self.assertEqual(to_cnf(expr('a | b')), Expr('|', 'a', 'b'))
def test_complex_example_Norvig(self):
"""logicutils - (P&Q) | (~P & ~Q) in CNF"""
self.assertEqual(str(to_cnf('(P&Q) | (~P & ~Q)')),
str('((~P | P) & (~Q | P) & (~P | Q) & (~Q | Q))'))
def test_singleton(self):
"""logicutils - singletons are already in CNF"""
self.assertEqual(to_cnf(expr('a')), Expr('a'))
