Landon Curt Noll
c457b16358
Renamed `ioccc.ico` to `favicon.ico`. Correctly added use of `favicon.ico` to all constructed HTML headers. Fixed the smart quote in HTML elements problem. Moved HTML "DO NOT EDIT" comments down below at the bottom of the HTML phase 1 section. According to to the Nu Html Checker, a charset attribute on a meta element found after the first 1024 bytes. Changed `bin/md2html.sh` VERSION from "1.1.3 2024-03-28" to "1.2 2024-03-30". Improved `bin/gen-status.sh` to adjust the "status_update" value only when the "contest_status" is changed. Performed a `make www` to perform and test the above under macOS.
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?
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.