def complete_column(carry_out: int, Carry_Out_Dig: PyValue, sum_dig: int,
Sum_Dig: PyValue, digits_in: List[int], Leading_Digits):
"""
If Sum_Dig (the variable representing the digit in the sum for this column) is not yet instantiated,
instantiate it to sum_dig (if that digit is available). If Sum_Dig is already instantiated, ensure
it is consistent with the sum_dig. Instantiate Carry_Out_Dig to carry_out.
"""
# Is Sum_Dig uninstantiated? If so, instantiate it to sum_digit if possible.
# Then instantiate Carry_Out_Dig, and return (yield) digits_in with sum_digit removed.
if not Sum_Dig.is_instantiated():
if sum_dig not in digits_in:
# sum_dig is not available in digits_in. Fail, i.e., return instead of yield.
return
# sum_dig is available in digits_in. Give it to Sum_Dig as long as this does not give
# 0 to one of the leading digits.
if sum_dig != 0 or all(Sum_Dig is not LD for LD in Leading_Digits):
for _ in unify_pairs([(Carry_Out_Dig, carry_out),
(Sum_Dig, sum_dig)]):
# Remove sum_digit from digits_in
i = digits_in.index(sum_dig)
yield digits_in[:i] + digits_in[i + 1:]
# If Sum_Dig is instantiated, is it equal to sum_digit?
# If so, instantiate Carry_Out_Dig and return the current digits_in.
elif sum_dig == Sum_Dig.get_py_value():
for _ in unify(Carry_Out_Dig, carry_out):
yield digits_in
def connected(S1: PyValue, Line_Dist: PyValue, S2: PyValue):
# S1: Union[PyValue, Var], Line_Dist: Var, S2: Union[PyValue, Var
"""
Are stations S1 and S2 connected on the same train line?
If so, which line is it, and how many stations are between them?
Line_Dist will be unified with (line, count_of_stations)
"""
# print(f'-> connected({S1}, {Line_Dist}, {S2})?')
Line = PyValue()
# Can use either forall or nested for _ in has_station's
# for _ in forall([lambda: has_station(Line, S1),
# lambda: has_station(Line, S2)]):
for _ in has_station(Line, S1):
for _ in has_station(Line, S2):
# Ensure that S1 != S2
if S1 != S2:
line = Line.get_py_value()
stations = lines[line]
pos1 = stations.index(S1.get_py_value())
pos2 = stations.index(S2.get_py_value())
yield from unify(Line_Dist, (line, abs(pos1 - pos2)))
