def last_pair(lst):
if utility.is_null(lst):
raise ValueError('empty list')
if utility.is_null(utility.cdr(lst)):
return utility.car(lst)
else:
return last_pair(utility.cdr(lst))
def square_list(list):
if utility.is_null(list):
return utility.list()
else:
return utility.cons(
square(utility.car(list)),
square_list(utility.cdr(list)))
def reverse(lst):
if utility.is_null(lst):
return None
elif utility.length(lst) == 1:
return lst
else:
x = utility.car(lst)
xs = utility.cdr(lst)
return utility.append(reverse(xs), utility.list(x))
def same_parity_iter(a):
"""
:type a: FunctionType | object
:return:
"""
if is_null(a):
return None
else:
b = car(a) # type: int
if is_even(x - b):
return cons(b, same_parity_iter(cdr(a)))
else:
return same_parity_iter(cdr(a))
def deep_reverse(lst):
def deep_reverse_element(a):
if callable(a):
return utility.list(deep_reverse(a))
else:
return utility.list(a)
def deep_reverse_of_length_one(lst):
return deep_reverse_element(utility.car(lst))
# utility.print_list(lst)
if utility.is_null(lst):
return None
elif utility.length(lst) == 1:
return deep_reverse_of_length_one(lst)
else:
x = utility.car(lst)
xs = utility.cdr(lst)
x_rev = deep_reverse_element(x)
xs_rev = deep_reverse(xs)
return utility.append(xs_rev, x_rev)
def for_each(f, lst):
if not utility.is_null(lst):
f(utility.car(lst))
for_each(f, utility.cdr(lst))
def accumulate(op, initial, list):
if is_null(list):
return initial
else:
return op(car(list), accumulate(op, initial, cdr(list)))
def subsets(l):
if is_null(l):
return list(list())
rest = subsets(cdr(l))
return append(rest, map(lambda x: cons(car(l), x) , rest))
def iter(things, answer):
if is_null(things):
return answer
else:
iter(cdr(things), cons(answer, square(car(things))))