def conclude(self, assumptions):
'''
Try to automatically conclude this bi-directional implication by
reducing its operands to true/false.
'''
from . import iff_t_t, iff_t_f, iff_f_t, iff_f_f, true_iff_true, false_iff_false
if self in {true_iff_true, false_iff_false}:
# should be proven via one of the imported theorems as a simple
# special case
try:
self.evaluation(assumptions)
except BaseException:
return self.prove()
try:
# try to prove the bi-directional implication via evaluation reduction.
# if that is possible, it is a relatively straightforward thing to
# do.
return Operation.conclude(assumptions)
except BaseException:
pass
try:
# Use a breadth-first search approach to find the shortest
# path to get from one end-point to the other.
return TransitiveRelation.conclude(self, assumptions)
except BaseException:
pass
# the last attempt is to introduce the Iff via implications each way, an
# essentially direct consequence of the definition.
return self.conclude_by_definition(assumptions)
def conclude(self, assumptions):
from proveit.logic import FALSE
if is_irreducible_value(self.lhs) and is_irreducible_value(self.rhs):
# prove that two irreducible values are not equal
return self.lhs.not_equal(self.rhs, assumptions)
if self.lhs == FALSE or self.rhs == FALSE:
try:
# prove something is not false by proving it to be true
return self.conclude_via_double_negation(assumptions)
except BaseException:
pass
if hasattr(self.lhs, 'not_equal') and is_irreducible_value(self.rhs):
try:
return self.lhs.not_equal(self.rhs, assumptions)
except BaseException:
pass
if hasattr(self.lhs, 'deduce_not_equal'):
# If there is a 'deduce_not_equal' method, use that.
# The responsibility then shifts to that method for
# determining what strategies should be attempted
# (with the recommendation that it should not attempt
# multiple non-trivial automation strategies).
eq = self.lhs.deduce_not_equal(self, assumptions)
if eq.expr != self:
raise ValueError("'deduce_not_equal' not implemented "
"correctly; must deduce the 'inequality' "
"that it is given if it can: "
"'%s' != '%s'" % (eq.expr, self))
return eq
try:
return self.conclude_as_folded(assumptions)
except BaseException:
# try the default (reduction)
return Operation.conclude(assumptions)
def conclude(self, assumptions):
from proveit.logic import FALSE
if isIrreducibleValue(self.lhs) and isIrreducibleValue(self.rhs):
# prove that two irreducible values are not equal
return self.lhs.notEqual(self.rhs)
if self.lhs == FALSE or self.rhs == FALSE:
try:
# prove something is not false by proving it to be true
return self.concludeViaDoubleNegation(assumptions)
except:
pass
if hasattr(self.lhs, 'notEquals') and isIrreducibleValue(self.rhs):
try:
return self.lhs.notEqual(self.rhs, assumptions)
except:
pass
try:
return self.concludeAsFolded(assumptions)
except:
return Operation.conclude(assumptions) # try the default (reduction)
