Author:

• Name: E. Jay Berkenbilt
  Location: US - United States of America (United States)

To build:

    make all

To use:

    ./ejb level

where level is a value from -128 to 127.

Try:

    ./try.sh

Judges’ remarks:

A negative argument plays the patience puzzle. An argument greater than 0 plays the Tower of Hanoi puzzle. In either case the absolute value of the argument specifies the size of the respective puzzle. Refer to the web pages hanoi.html and patience.html for more information on these puzzles.

Of course, you need a different kind of “patience” if you give the argument 127 to this program and want to see it finish!

We note that this also works under macOS just fine.

Author’s remarks:

What this program does

Output solution to Towers of Hanoi for five rings:

    ./ejb 5

The format of the output for the Towers of Hanoi case is simply a text description of how to solve the puzzle.

Output solution to the Patience puzzle for six rings:

    ./ejb -6

For the patience puzzle, the output is a sequence binary codes representing successive states of the puzzle. The rightmost digit represents the first ring. A 1 means the ring is on the U; a 0 means it is off the U. The program prints the word "Invalid" in response to illegal command line parameters.

Motivation

Most people who have written software for other people have been asked to count lines of code. Naturally, this brings up the controversial question of exactly what defines a line of code. This program serves to show that counting semicolons will not always provide a meaningful measure of code size. This is especially true in this program where the number of semicolons itself is ambiguous. Does it have two or three? In addition, the only C keyword this program uses besides type names and qualifiers is return, and the only function defined in the code is main(). The level of complexity of the program without multiple semicolons, statements, and functions is achieved by abusing C operators, especially the comma operator. Considerable use of ||, &&, and ?: helps too. In addition, main() is called recursively. The NULL pointer that terminates argv is used to pass additional information into main(). Even though the algorithms used by this code are simple, this program is still hard to follow even when indented properly. (It is pretty hard to indent this code reasonably, however.)

Although this program has only been tested on UNIX systems it will probably run on just about any machine with an ANSI C compiler. It does not use the C preprocessor at all. The only functions it uses are atoi(3), malloc(3), memset(3), printf(3), and puts(3). It does, however, require that the architecture it runs on have bytes that are at least eight bits long and pointers that are at least four bytes long. In addition, it requires an ANSI compiler since it uses signed char and ANSI-style function declarations.

Primary files

• ejb.c - entry source code
• Makefile - entry Makefile
• ejb.orig.c - original source code
• hanoi.html - about the Towers of Hanoi puzzle
• patience.html - about the Patience puzzle
• try.sh - script to try entry

Secondary files

• 1993_ejb.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• hanoi.md - markdown source for hanoi.html
• .path - directory path from top level directory
• patience.md - markdown source for patience.html
• index.html - this web page

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