def prove(kb, ans_body, indent=""):
"""returns True if kb |- ans_body
"""
kb.display(2, indent, 'yes <-', ' & '.join(ans_body))
if ans_body:
selected = ans_body[0] # select first atom from ans_body
if selected in kb.askables:
return (yes(input("Is " + selected + " true? "))
and prove(kb, ans_body[1:], indent + " "))
else:
return any(
prove(kb, cl.body + ans_body[1:], indent + " ")
for cl in kb.clauses_for_atom(selected))
else:
return True # empty body is true
def prove_all_ass(self, ans_body, assumed=set()):
"""returns a list of sets of assumables that extends assumed
to imply ans_body from self.
ans_body is a list of atoms (it is the body of the answer clause).
assumed is a set of assumables already assumed
"""
if ans_body:
selected = ans_body[0] # select first atom from ans_body
if selected in self.askables:
if yes(input("Is "+selected+" true? ")):
return self.prove_all_ass(ans_body[1:],assumed)
else:
return [] # no answers
elif selected in self.assumables:
return self.prove_all_ass(ans_body[1:],assumed|{selected})
else:
return [ass
for cl in self.clauses_for_atom(selected)
for ass in self.prove_all_ass(cl.body+ans_body[1:],assumed)
] # union of answers for each clause with head=selected
else: # empty body
return [assumed] # one answer
def ask_askables(kb):
return {at for at in kb.askables if yes(input("Is "+at+" true? "))}