def formulaVars(self, f: Formula) -> Set[str]:
""" List variables in formula f.
This depends on correct implementation of subf() and Variable.name.
"""
if isinstance(f, Variable):
return set([f.name()])
return set.union(set(), *(self.formulaVars(sf) for sf in f.subf()))
def formulaIsSatisfied(self, f: Formula, v: Valuation):
if isinstance(f, Variable):
return v[f.name()]
elif isinstance(f, Negation):
return not self.formulaIsSatisfied(f.subf()[0], v)
elif isinstance(f, Conjunction):
return all(self.formulaIsSatisfied(sf, v) for sf in f.subf())
elif isinstance(f, Disjunction):
return any(self.formulaIsSatisfied(sf, v) for sf in f.subf())
elif isinstance(f, Implication):
return (not self.formulaIsSatisfied(
f.subf()[0], v)) or self.formulaIsSatisfied(f.subf()[1], v)
elif isinstance(f, Equivalence):
return self.formulaIsSatisfied(f.subf()[0],
v) == self.formulaIsSatisfied(
f.subf()[1], v)
else:
raise TypeError("Formula expected, got %s" % repr(f))
def formulaDeg(self, f: Formula) -> int:
if isinstance(f, Variable):
return 0
return sum(self.formulaDeg(sf) for sf in f.subf()) + 1
