Cody Boone Ferguson
61bd64220c
The mobile About menu was missing the IOCCC markdown guidelines. This has been added to the mobile menu but moved to 'Status' which is where guidelines are (it has been renamed to be 'IOCCC Markdown Guidelines' to match the style of the other items in that menu). The About menu now has two more links, one for the website tools and the other for the include files of the tools. It might be, looking at the generated html files, better to have another menu instead, but what that should be is unclear. The reason it might be better is because the 'About' menu is rather long. In retrospect it might be better to not have the script include files in the html files but this can be decided and dealt with later. The script bin/find-missing-links.sh now ignores the directory NOTES/. A better approach might be using git ls-files --exclude but a quick test did not work right. Another option, at least for NOTES/, might be to use 'git ls-files --exclude-standard'. The bin/index.html file has been updated. Run make www to rebuild all html files.
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.