Note: This post was edited for clarity.
This JAPH uses a Turing machine. The machine accepts any string that ends in '\n' and allows side effects. This lets us print the value of the tape as it encounters each character. While the idea of using lambda functions as side effects in a Turing machine is a little bizarre on many levels, we work with what we have. And Python is multi-paradigmatic, so what the heck.
import re
def turing(tape, transitions):
# The tape input comes in as a string. We approximate an infinite
# length tape via a hash, so we need to convert this to {index: value}
tape_hash = {i: x for i, x in enumerate(tape)}
# Start at 0 using our transition matrix
index = 0
state = 0
while True:
value = tape_hash.get(index, '')
# This is a modified Turing machine: it uses regexen
# and has side effects. Oh well, I needed IO.
for rule in transitions[state]:
regex, next, direction, new_value, side_effect = rule
if re.match(regex, value):
# Terminal states
if new_value in ('YES', 'NO'):
return new_value
tape_hash[index] = new_value
side_effect(value)
index += direction
state = next
break
assert 'YES' == turing('just another python hacker\n', [
# This Turing machine recognizes the language of strings that end in \n.
# Regex rule, next state, left/right = -1/+1, new value, side effect.
[ # State 0:
[r'^[a-z ]$', 0, +1, '', lambda x: print(x, end='')],
[r'^\n$', 1, +1, '', lambda x: print(x, end='')],
[r'^.*$', 0, +1, 'NO', None],
],
[ # State 1:
[r'^$', 1, -1, 'YES', None]
]
])
Obfuscation again consists of converting the above code into lambda functions using Y combinators. This is a nice programming exercise, so I’ve left it out of this post in case anyone wants to try. The Turing machine has to return 'YES' to indicate that it accepts the string, thus the assertion. Our final obfuscated JAPH is a single expression.
assert'''YES'''==(lambda g:(lambda f:g(lambda arg:f(f)(arg)))(lambda f:g(
lambda arg: f(f)(arg))))(lambda f: lambda q:[(lambda g:(lambda f:g(lambda
arg:f(f)(arg)))(lambda f: g(lambda arg:f(f)(arg))))(lambda f: lambda x:(x
[0][0]if x[0] and __import__('re').match(x[0][0][0],x[1])else f([x[0][1:]
,x[1]]))) ([q[3][q[1]],q[2].get(q[0],'')])[4](q[2].get(q[0],'')), (lambda
g:(lambda f:g(lambda arg:f(f)(arg))) (lambda f:g(lambda arg:f(f)(arg))))(
lambda f:lambda x:(x[0][0]if x[0] and __import__('re').match(x[0][0][0],x
[1])else f([x[0][1:],x[1]])))([q[3][q[1]],q[2].get(q[0],'')])[3]if(lambda
g:(lambda f:g(lambda arg:f(f)(arg))) (lambda f:g(lambda arg:f(f)(arg))))(
lambda f:lambda x:(x[0][0]if x[0]and __import__('re').match(x[0][0][0],x[
1]) else f([x[0][1:],x[1]])))([q[3][q[1]],q[2].get(q[0],'')])[3]in('YES',
'NO')else f([q[0]+(lambda g:(lambda f:g(lambda arg:f(f)(arg)))(lambda f:g
(lambda arg:f(f)(arg))))(lambda f:lambda x:(x[0][0]if x[0]and __import__(
're').match(x[0][0][0],x[1])else f([x[0][1:], x[1]])))([q[3][q[1]], q[2].
get(q[0],'')])[2],(lambda g:(lambda f:g(lambda arg: f(f)(arg)))(lambda f:
g(lambda arg:f(f)(arg))))(lambda f:lambda x:(x[0][0]if x[0]and __import__
('re').match(x[0][0][0],x[1])else f([x[0][1:], x[1]])))([q[3][q[1]],q[2].
get(q[0],'')])[1],q[2],q[3]])][1])([0,0,{i:x for i,x in enumerate('just '
'another python hacker\n')}, [[[r'^[a-z ]$',0,+1,'',lambda x:print(x,end=
'')], [r'^\n$',1,+1,'',lambda x:print(x, end='')],[r'^.*$',0,+1,'''NO''',
lambda x:None]], [[r'''^$''',+1,-1,'''YES''', lambda x: None or None]]]])