Cody Boone Ferguson
3deb7ae603
Amongst the changes here is that we do not need to have the hex or html
code (numbers) for open and close parentheses (in links) as there are
names. '(' is & followed by lpar; and the ')' is the same but 'rpar;'
instead. This makes it easier to remember and type and it generates the
same html as well (they are all valid). Now the markdown files are
consistent in this (in some cases hex was used and in others the html
code).
Although many markdown files were updated no html files needed to be
updated as it generates the same html. Even so I ran the appropriate
rules to do so just to verify this.
3.1 KiB
To build:
make
To use:
./timwi < bf_program
Try:
./try.sh
Judges' remarks:
Unlike most BF interpreters that we have been receiving for the last few years, this one, in our opinion, is the most obfuscated albeit the most discourteous to the language it interprets. A simple 3-character fix will make it slightly less so.
Quite a few BF programs found on the Net expect byte-based memory, quite a few exceed the capacity of this interpreter, but there are many that work. Some small quines work, some don't.
Why?
Author's remarks:
This is an interpreter for the programming language BrainFuck (BF).
Input must be provided in the following format: First a sequence of integers
separated by whitespace (this will be the input to the BF program), then a :
(colon), then the BF program itself.
You must not pass any command-line arguments.
Features
-
Supports the complete set of 8 BF instructions (
+-<>[].,). -
Supports the use of alternative characters for some of those instructions. Use this to obfuscate your BF programs!
For a challenge, figure out what this obfuscated BF program does:
J4mzt?Vazexx-20d~&&~AxdUV!x(~Jz&V)x*(P=J)JUN(dizz)xx_!xx'0&{Vz;}&JjIt takes two integers as input and outputs one integer.
-
Ignores all whitespace (newlines, spaces and tabs) in the input program.
Limitations
Since the program, naturally, uses ints, the calculations must not exceed the
range of an int. (But then again, you can use the integer overflow to further
obfuscate your BF programs in creative ways!)
You are limited to 3125 input integers and 3125 instructions. If you exceed one of these limits, the behaviour is undefined.
Obfuscations
Some of the superficial obfuscations are pretty obvious: I'm using #defines to
make everything look nice and lineal, and the program is merely a recursive
main() function with only a single return statement which uses nested ternary
operators to make even the pre-processed code unreadable.
However, the more subtle obfuscations relate to the way the program works.
After applying the pre-processing, you will see a lot of 1+1+1...etc., and
even if you replace these with their result, those numbers will still not
represent (or even relate to) the ASCII codes of the BF instructions.
The program will first read in all the input integers, but it will begin execution immediately and only read program instructions as they are needed. Yet there is no global variable storing how far it has read! Perhaps the hardest thing to figure out is how it finds the matching square brackets.