Cody Boone Ferguson
af5482825c
The sections have been modified a fair amount. The Entries menu has been extended to have: Fixing entries, Updating author info, Thanks for the help. The first two were moved from FAQ and the last one from About. The rationale for these, in order: entries and authors have to do with entries and most of the help involves entries. It also has to do with website but in 'about' it does not seem the right place, unless maybe it is renamed to 'Credits' or something (I am not suggesting this one way or the other). This one is debatable but that was the rationale. The Status menu has been extended to have: Markdown guidelines and Security policy. The rationale is that the markdown guidelines are part of contest guidelines and the security policy is about the status of the entries and how if there are any security problems they will not be addressed (instead of about the IOCCC). The FAQ was extended to have: Compiling entries, Running entries, How to help. The reason to not have compiling and running entries under Entries is because this is 'how to' and also the menu was too long. How to help seems like a good idea under FAQ too (was in About). About was extended to have the new 'about.html' page (from about.md). This is a rare case where a new file is useful as it fits under 'About'. The menu now is: Home page, About the IOCCC, The Judges, Contact us. I was pondering the 'About [the IOCCC]' at the top and also naming it 'About us' but it seemed like a link to index.html was necessary and as for 'about us' it seemed less clear as to whether it was about the judges or the contest itself. The FAQ has been updated slightly for this. After further inspection the bin/index.html and the inc/index.html links were removed from the about section. With these changes, renaming an item or slight reordering notwithstanding, I believe that #2006 is probably in good shape.
To build:
make all
To use:
echo text | ./fine
Try:
./try.sh
Make sure that you read the last line backwards! Credit goes to Merlyn LeRoy (Brian
Westley) for that. See his 22 August 1992
rec.puzzles
post.
Some others come from his 1989 entry as well. To
those who have a harder time reading backwards it says: Gary lent the rug,
rotated from the rug gary lent!
Judges' remarks:
This filter, 80 chars plus a newline, fits into a single line on most terminals, unless your terminal has a line wrap mis-feature :-).
Note in 2023: fixing this entry to work with modern systems increased the size, originally to 106 characters but it was dropped back down to 80 with clever use of the Makefile.
This entry is likely one of the smallest C implementations of this filter, excluding programs that resort to command line or include file tricks.
How does this program work? Which 3 bytes of C code can be changed into 2 bytes, allowing the program to still work, but also stripping the high bit off some input?
NOTICE to those who wish for a greater challenge:
If you want a greater challenge, don't read any further: just try to understand the program via the source.
If you get stuck, come back and read the author's remarks for additional hints and information.
Author's remarks:
The author wishes to thank J Greely for the last 6 bytes.
Here's about how it does it:
NOTE: Bits are referred to as 76543210, high to low.
-
Get the character in variable
a. Note the fun way we check forEOF. (thanks J). -
Reverse bit 6, and strip bit 5. Bit 6 determines (mostly) whether or not this character is a letter. Bit 5 would determine case if we cared. Assign this value to variable
b(We need to save it, since we need to make 2 comparisons and maybe one operation with this value). We can't abuse our first variable, since it saves the bits we're changing. -
Check this value to see if it is a letter. It must be non-zero - if it is zero, then we have either the
@(64) or the`(96). It also must be less than 27 - this checks the range for letters as well as implicitly checking the value of bit 6 (if it was originally clear, it is set now, sobwould be too big). -
If it is not a letter, the conditional expression inside of the
putchar()returns the original character (a). Otherwise, it returns a really messy expression that performs the actual rotation and fixes the fifth and sixth bits:- A. Subtract 1, to get into the range 0-25 (for the modulo operation).
- B. Add 13 to the character. Steps A and B are combined.
- C. Take this modulo 26 to make the addition wrap around.
- D. Fix bits 5 and 6, based on variable
a. - E. Add 1 back in (we took it out in step A.) This is okay to do after
step D, because we know the addition won't trickle up past the fourth bit
(
bwould have to be 31 for this to happen).
Notice that this implementation operates only on characters with the high bit clear. The high bit can be ignored without changing the size of the program. Also, if you know you are only dealing with seven bit data, the size can be reduced by one byte. These are left as exercises for the student.