ioccc/1996/dalbec/README.md at 4d2e18db47cc4e7f7ab95147b2fdabdbca4b47c5

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Landon Curt Noll 4ee4c731f7 convert markdown copyright TAB chars into SPACE chars

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.

2024-06-22 22:15:25 -07:00

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To build:

    make all

To use:

    ./dalbec

Try:

    ./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.

... 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:

The use of easily-confused variable names.
Using the implicit !=0 in conditional expressions.
Substituting expressions such as !a for 0 where a!=0 and !a for 1 where a==0.
The fact that main() is a single expression and so beautifies poorly.
The fact that main() is used:
- to compute powers in modular arithmetic.
- to recursively call itself in the main loop.

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