def helper(f, result):
if is_predicate(f) and len(f.args) == 0:
result.add(f)
else:
for x in f.args:
helper(x, result)
return result
def evaluate_prop(f, assignment):
"""Evaluate a propositional formula with respect to the given assignment.
# The assignment should be a dict with 2 keys: 'True' and 'False'. The values
# for those keys should be a collection of strings corresponding to
# the operator names - predicates with 0 arity (acting as propositions).
The assignment maps propositions (0-ary predicates) to True or False.
"""
if f.op == OP_TRUE:
return True
elif f.op == OP_FALSE:
return False
elif f.op == OP_NOT:
return not evaluate_prop(f.args[0], assignment)
elif f.op == OP_AND:
return all(evaluate_prop(x, assignment) == True for x in f.args)
elif f.op == OP_OR:
return any(evaluate_prop(x, assignment) == True for x in f.args)
elif f.op == OP_IMPLIES:
args = [evaluate_prop(x, assignment) for x in f.args]
return not (args[0] == True and args[1] == False)
elif f.op == OP_IMPLIED_BY:
args = [evaluate_prop(x, assignment) for x in f.args]
return not (args[0] == False and args[1] == True)
elif f.op == OP_EQUIVALENT:
args = [evaluate_prop(x, assignment) for x in f.args]
return (args[0] == args[1])
elif is_predicate(f) and len(f.args) == 0:
try:
return assignment[f]
except KeyError:
raise EvaluationError('Predicate "{0}" is not in the assignment.'.
format(str(f)))
else:
msg = ('The Quine-McCluskey algorithm is defined only for '
'propositional logic. The operator "{0}" is not defined '
'in propositional logic.'.format(f))
raise EvaluationError(msg)
def formula_to_rst(f):
""" Convert a FOL formula to an RST tree. """
get_log().debug(str(f))
if f.op == OP_AND:
msgs = [formula_to_rst(x) for x in f.args]
m = Message("Conjunction", None, *msgs)
# test = lambda x: (x.op == '&' or x.op == '|')
# if any(map(test, f.args)):
# m.marker = ', and'
# else:
m.marker = "and"
return m
if f.op == OP_OR:
msgs = [formula_to_rst(x) for x in f.args]
m = Message("Disjunction", None, *msgs)
# test = lambda x: (x.op != 'forall' and
# x.op != 'exists')
# if any(map(test, f.args)):
# m.marker = ', or'
# else:
m.marker = "or"
return m
if f.op == OP_IMPLIES:
msgs = [formula_to_rst(x) for x in f.args]
m = Message("Imply", msgs[0], msgs[1])
return m
if f.op == OP_IMPLIED_BY:
msgs = [formula_to_rst(x) for x in f.args]
m = Message("Imply", msgs[1], msgs[0])
return m
if f.op == OP_EQUIVALENT:
msgs = [formula_to_rst(x) for x in f.args]
m = Message("Equivalent", msgs[0], msgs[1])
return m
if f.op == OP_EQUALS:
msgs = [formula_to_rst(x) for x in f.args]
m = Message("Equality", msgs[0], *msgs[1:])
return m
if f.op == OP_NOTEQUALS:
msgs = [formula_to_rst(x) for x in f.args]
m = Message("Inequality", msgs[0], *msgs[1:])
return m
if f.op == OP_FORALL:
vars = [formula_to_rst(x) for x in f.vars]
msgs = [formula_to_rst(x) for x in f.args]
m = Message("Quantifier", vars, *msgs)
m.marker = "for all"
return m
if f.op == OP_EXISTS:
vars = [formula_to_rst(x) for x in f.vars]
msgs = [formula_to_rst(x) for x in f.args]
m = Message("Quantifier", vars, *msgs)
if len(f.vars) == 1:
m.marker = "there exists"
else:
m.marker = "there exist"
return m
if f.op == OP_NOT and is_predicate(f.args[0]):
get_log().debug("negated predicate: " + str(f))
arg = f.args[0]
m = PredicateMsg(arg, *[formula_to_rst(x) for x in arg.args])
m._features = {"NEGATED": "true"}
return m
if f.op == OP_NOT and is_variable(f.args[0]):
get_log().debug("negated variable: " + str(f))
arg = f.args[0]
m = NounPhrase(PlaceHolder(arg.op), Word("not", "DETERMINER"))
return m
if f.op == OP_NOT:
get_log().debug("negated formula: " + str(f))
msgs = [formula_to_rst(x) for x in f.args]
m = Message("Negation", msgs[0], *msgs[1:])
m.marker = "it is not the case that"
return m
if is_predicate(f):
get_log().debug("predicate: " + str(f))
return PredicateMsg(f, *[formula_to_rst(x) for x in f.args])
if is_function(f):
get_log().debug("function: " + str(f))
return PlaceHolder(f.op, PredicateMsg(f, *[formula_to_rst(x) for x in f.args]))
else:
get_log().debug("None: " + repr(f))
return PredicateMsg(f)
