## To build:

``` <!---sh-->
    make
```


### Bugs and (Mis)features:

The current status of this entry is:

> **STATUS: INABIAF - please DO NOT fix**

For more detailed information see [2001/cheong in bugs.html](../../bugs.html#2001_cheong).


## To use:

``` <!---sh-->
    ./cheong digits
```


## Try:

``` <!---sh-->
    ./try.sh
```


## Judges' remarks:

Be sure to give an even number of digits in the argument.  Add a
leading 0 if needed.

The source code is nice, compact, and self documenting
as all good programs should be!  :-)


## Author's remarks:

### Operation

Compile normally and run with one argument, an integer with 2n digits.
Program will return the integer part of its square root (n-digits).
For example,

``` <!---sh-->
    $ cc -o cheong cheong.c
    $ ./cheong 1234567890
    35136
    $ ./cheong 0200000000000000000000000000
    14142135623730
```

Deviation from these instructions will cause undefined results. :-)

### Portability

This program runs normally on any ANSI C compiler and is ASCII dependent.

Strict compiling gives just one unavoidable warning:

``` <!---sh-->
    gcc -ansi -Wall cheong.c
    cheong.c:3: warning: third argument of `main' should probably be `char **'
```

### Obfuscation

The main obfuscation is the algorithm used to calculate square roots,
sometimes known as the longhand method.  The basic algorithm is itself
obfuscated in that it only uses subtraction to calculate square roots.
For a detailed explanation, check Google or see Jack Crenshaw's article
at
<https://web.archive.org/web/20011215124349/http://www.embedded.com/98/9802fe2.htm>.

This program uses an even more obscured version which includes the following:

- A single string is used to store two numbers of different lengths
- Operations are done in a weird hybrid of base 10 and base 20
- Subtraction is done addition style, i.e. `4 - 8` equals `6` carry a `-1`
- Recursive calls to `main()`

#### Minor obfuscations:

- Self documenting whitespace in rectangular code block, for fun and glory (view
with fixed-width font)
- Integer constants adjusted to less meaningful values, just for added confusion
- Hard-to-read, meaningless variable names to spite the reader

#### Challenges for the masses:

- What are the meanings [sic, plural] of the variable `o`?
- Why is `(c+999)%10-(D[I]+92)%10` not equivalent to `(c-D[I]+7)%10`?
- How does the program terminate?
- Is the programmer sane? ;-)

### Appreciation

Thanks goes out to Bobby Rohde for numerous suggestions on how to shorten
the program.


<!--

    Copyright © %%DATE_RANGE%% 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/

-->