Landon Curt Noll
4ee4c731f7
While not strictly necessary, replacing the two ASCII tab characters in the markdown copyright comment makes it easier to detect problematic TAB indentation within markdown files. After this commit, only 90 markdown files have leading ASCII TAB characters. And again, while not strictly necessary, we can consider running expand on those 90 markdown files to see what effect that might have on the HTML files they produce. Replace leading ASCII TAB characters with multiples of 8 ASCII SPACE characters (the default action of the `expand(1)` tool) might have an negative effect on some HTML formatting where **hack-a-round** formatting was attempted to fix broken indentation caused by problematic ASCII TAB characters. Think of this as a baseline for evaluating leading TAB characters within markdown files. TODO: Consider either using `expand(1)` to replace leading ASCII TAB characters with multiples of 8 ASCII SPACE characters AND/OR modifying the appropriate `bin` tool to convert leading ASCII TAB characters into multiples of 8 ASCII SPACE characters.
86 lines
2.2 KiB
Markdown
86 lines
2.2 KiB
Markdown
## To build:
|
|
|
|
``` <!---sh-->
|
|
make all
|
|
```
|
|
|
|
|
|
## To use:
|
|
|
|
``` <!---sh-->
|
|
./dalbec
|
|
```
|
|
|
|
|
|
## Try:
|
|
|
|
``` <!---sh-->
|
|
./try.sh
|
|
```
|
|
|
|
Why does the output end with 121?
|
|
|
|
|
|
## Judges' remarks:
|
|
|
|
The output is mis-leading ... why does it also print 2047?
|
|
|
|
For a hint see
|
|
[https://web.archive.org/web/20000510191341/https://www.utm.edu/research/primes/prove2.html](https://web.archive.org/web/20000510191341/https://www.utm.edu/research/primes/prove2.html).
|
|
|
|
|
|
... and then try to understand the source! :-)
|
|
|
|
We (the judges) recommend that you take the time needed to understand
|
|
how this program works. The source is small enough to make the effort
|
|
reasonable, and complex enough to make it interesting.
|
|
|
|
|
|
## Author's remarks:
|
|
|
|
This program assumes that your terminal wraps lines automatically.
|
|
If this is not the case, you may need to change the space in the
|
|
"printf" format string to a newline character.
|
|
|
|
An extra feature of this program is that it allows you (in most
|
|
cases) to estimate the stack space available to programs on your
|
|
system. Simply allow the program to run to completion. The stack
|
|
space is roughly proportional to the last number printed.
|
|
|
|
(On SunOS/cc, the proportionality constant is about 48 bytes.)
|
|
|
|
On completion, the program produces a core file that may be used to
|
|
refine this estimate. (Or you could try typing `limit` if you're
|
|
running `csh`.) In rare cases the stack space may exceed `24*INT_MAX`
|
|
bytes, in which case the program will produce an inaccurate estimate.
|
|
|
|
This program is obfuscated by:
|
|
|
|
1. The use of easily-confused variable names.
|
|
|
|
2. Using the implicit `!=0` in conditional expressions.
|
|
|
|
3. Substituting expressions such as `!a` for `0` where `a!=0` and `!a` for `1`
|
|
where `a==0`.
|
|
|
|
4. The fact that `main()` is a single expression and so beautifies poorly.
|
|
|
|
5. The fact that `main()` is used:
|
|
- to compute powers in modular arithmetic.
|
|
- to recursively call itself in the main loop.
|
|
|
|
|
|
<!--
|
|
|
|
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
|
|
|
You are free to share and adapt this file under the terms of this license:
|
|
|
|
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
|
|
|
|
For more information, see:
|
|
|
|
https://creativecommons.org/licenses/by-sa/4.0/
|
|
|
|
-->
|