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The International Obfuscated C Code Contest

2000/jarijyrki - Best of Show

← 2000/dlowe ↑ 2000 ↑ 2000/natori → C code Makefile Inventory ✓

Authors:

To build:

    make

NOTE: this entry requires the X11/Xlib.h header file and the X11 library to compile. For more information see the FAQ on “X11”.

To use:

    ./jarijyrki < infile.info > outfile.info

You will need a system capable of displaying the results of X Window programs.

Try:

    ./jarijyrki < finance.sheet > myedits.info

Then click on cell C3 and type in the following:

    C5 C6 C7 @

Click on cell D4 and type in the following:

    C5 C6 C7 !

Hit ESC.

Now try running:

    ./jarijyrki < myedits.info

And observe that it matches what you had in the previous run!

NOTE: changing the dimension parameters (see the authors’ remarks) renders existing spreadsheet files unusable.

Judges’ remarks:

This entry is one of those that makes you wonder why some commercial software needs tens to hundreds of megabytesgigabytes to install! This entry does not simply do the basics, it includes graphing features. All this program needs now is a 1998/banks flight simulator!

Author’s remarks:

1. OVERVIEW

This program is an X-Windows based spreadsheet program. The main functions it supports are:

2. USAGE INSTRUCTIONS

2.1. Quick Guide

Starting
    ./jarijyrki < finance.sheet > myedits.info
Stopping

Use the ESC key.

Movement

Click the mouse or use the arrow keys.

Editing

The currently selected cell is always in the edit state. Press any key to add a character at the end of the formula; press backspace to delete the last one.

Formulas
    123.45
    A1 A2 +
    B1 B2 -
    C1 C2 *
    D1 D2 /
Pie charts
    A1 A2 A3 ...

Finish the formula with @ to create the pie chart.

Histograms
    A1 A2 A3 ...

Finish the formula with ! to create the histogram.

2.2. Starting and Loading Spreadsheets

To start the spreadsheet program with an existing spreadsheet, for instance finance.sheet, use the following command line:

    ./jarijyrki < finance.sheet

The file finance.sheet has been provided as an example. This file contains a set of financial numbers and two graphical entities - a pie chart and a histogram - based on them. We recommend starting the use of the program from this file, as a way to study and learn the formula language supported by the program.

To start the program with an empty sheet, use

    ./jarijyrki < /dev/null

Alternatively, /dev/zero could be used but that may not exist on all systems.

2.3. Exiting and Saving Spreadsheets

Normally the user obviously wants to edit the spreadsheet. After the spreadsheet program finishes, it outputs the edited spreadsheet to the standard output. Hence, when the spreadsheet window has come up, you’ve made your changes, and you press the ESC key the program finishes. To save the results in a file, the following typical command line would be used:

    ./jarijyrki < finance.sheet > myedits.info

2.4. Visual Overview

On top of the window the Formula Area shows the formula (or text) of the currently selected cell. The program starts with A1 as being the current cell. Below the Formula Area is the Column Letters Area: A, B, and so on. Correspondingly, on the left side of the window is the Row Numbers Area: 1, 2, and so on. The rest of the window is dedicated to the actual spreadsheet cells.

The example spreadsheet, finance.sheet, provided with this program contains two sets of numbers in the visible area of the spreadsheet. The top set of numbers forms the product-by-product turnover breakdown of an imaginary company. Below it is the yearly development of the company profits. On the top right corner is a pie chart showing the turnover breakdown in graphical form, and on the bottom right corner is a histogram showing the yearly development. If you scroll the window you can see additional data from the spreadsheet.

2.5. Movement and Scrolling

Use arrow keys to move left, right, up, and down among the cells. You may also click the mouse on a cell to cause it to be activated as the current one.

Note that it is not possible to move around the formula; the formula can only be edited from its end by adding or removing characters.

Going beyond the borders of the window results in scrolling the current view. It is not possible to go up from the first row or left from the first column; but it is possible to wrap back to start from the last row and last column.

2.6. Formulas

The spreadsheet formulas operate on a stack. Operands of an operation (e.g. plus) are first pushed to the stack and then the operation is performed. If a formula on a cell produces exactly one result then that is shown in the cell. Otherwise, the formula is interpreted as a string and shown as it is.

An example of a simple formula, simply specifying a number is

    123.50

Another simple formula refers to a cell:

    A1

This particular example formula referred to the first cell of the first row in the spreadsheet. Arithmetic operations require both arguments:

    A1 A2 +
    B1 B2 *
    C1 C2 -
    D1 D2 /

More complex formulae can be constructed by combining these simple ones:

    A1 A2 + 2 *

This example calculates the sum of the cells A1 and A2, and then multiplies the result by two.

The currently selected cell is always in a state where it can be edited. Press any key to add a character at the end of the formula; press backspace to delete the last character. Any resulting recalculations are immediately visible. (Note how much nicer this feature is as you get used to it, compared to the behaviour of certain commercial spreadsheet programs.)

2.7. Graphical Formulas

The program supports two types of graphical representations of the data in the cells: pie charts and histograms. The pie chart can consist of any number of slices, and is constructed by putting the pie amounts in stack and using the @ operator. The program automatically computes the relative size of the slices.

    A1 A2 A3 A4 @

This example would draw a pie chart of four cells, A1 to A4. The pie formula is shown above the pie for reference.

The histograms are drawn in a similar manner, by using the ! operator:

    A1 A2 A3 A3 !

2.8. Errors in Formulas

The program detects recursive reference attempts, references cells not containing a numerical value, attempts to define formulas with zero, two, or more results remaining on the stack, and syntax errors of formulas. Note that typically as the user types in a formula, it toggles between valid and invalid forms dynamically as all single character changes are immediately taken in account. This is not dangerous, just complete the formula and view the results.

Errors are signalled by showing the formula on a cell instead of the numerical value supposedly returned by it.

Division by zero results in an IEEE Inf number.

2.9. Compilation Parameters and Configuration

This section explains the meaning and rationale for the compile time parameters:

    -DC=XK_Up
    -DL=XK_Down
    -DO=XK_Left
    -DV=XK_Right
    -DR=XK_Escape
    -D_=XK_BackSpace

These definitions can be used to change the user interface of the program with respect to special keys. The first four define the movement operations and the latter two define the program termination and character deletion keys. Typical modifications to these parameters include changing character deletion to the key the user is most familiar with, which could also be XK_Delete. XK_Escape might be better in some cases as one of the function keys. Likewise for the arrow keys.

    -DU=40

This parameter defines the maximum dimensions of the stored and handled spreadsheet (but see section 4.4 for a warning about changing this without thinking about the consequences!).

    -DT=98

This parameter defines the maximum length of a formula in one cell. Note the warning in section 4.4.

    -Dz="(T+1)*U*U"

Defines the number of bytes in a spreadsheet file. The number is automatically adjusted when the spreadsheet size parameters are changed. Note the warning in section 4.4.

    -DQ=80
    -DS=20

These two parameters define the visual dimensions of a cell. Changing these may be necessary on your system if the default font sizes differ from those in the systems we’ve tested the program with. S also defines the size of the left (x1) and top margins (x2).

    -DN=10

This is the x-indentation of text inside a cell. Changing this may be necessary to suit other font sizes and different X environments.

    -DB=5

This is the y-indentation of text inside a cell. Changing this may be necessary to suit other font sizes and different X environments.

    -DG=23

This parameter is the number of cell rows visible at one time.

    -Dp=7

This parameter is one smaller than the number of cells columns visible at one time.

    -DM="((p+1)*Q)+S"
    -DH="(G*S)+S+S"

These parameters are the window x and y sizes of the spreadsheet program window. With these definitions, they are automatically reflecting the at-one-time-visible cell row/column amounts. Hence, we recommend changing the G and p parameters if you want to change the window size in normal cases. Experimentation with M and H can be used to get other types of effect such as adding a margin also at the bottom of the window.

3. IMPLEMENTATION

It’s better to just read the code. But note the use of stack in the implementation of @ and ! operators, and note the use of *#i in one of the macros (can you see why?). Extreme compression has been the key in writing this program. With compression comes the use of ASCII code numbers instead of character constants and so on. (This particular obfuscation is not really a desirable one as it is not completely portable. But it certainly was a necessary one.)

What does i(=) do or does it do anything? Why?

4. WARNINGS AND CAVEATS

4.1. X11 Paths in Compilation

The given Makefile may have to be edited to insert correct library and include file path names.

4.2. Font Sizes

We’ve tested the program with a limited amount of X servers. It is possible that other systems use default font sizes or other parameters that cause the visual looks to be different or perhaps even unusable; if this happens, changing compile-time parameters explained in section 2.8 might help.

4.3. Screen Sizes

The size of the window as it comes up - a parameter as defined in compile-time - has been set suitable for a small laptop screen. Larger screens may benefit from setting these parameters higher. Smaller screens require changing the parameters so that all of the window becomes visible.

4.4. Spreadsheet Dimension Changes

The size of the read, manipulated, and stored spreadsheets is defined by a compile time parameter. However, changing this parameter is not entirely trivial. The following constraints apply:

4.5. ASCII Reliance

The software relies on running on ASCII-based code system. Why? Because 32 is shorter than ' '.

4.6. Command Line Single Character Defines

The use of single character (e.g. G or p) for a -D option might break certain systems, if those characters are used in the included X header files in certain kinds of places. If this happens, you may move the offending character to a new name by exchanging it on the command line and in the program with another character. Note that there are no free characters in the program currently.

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