Best of Show:
Jari Arkko
Kauppalantie 25A7,
02700 Kauniainen,
Finland
http://www.arkko.com
Jyrki Holopainen
Forsellesintie 1-3A10,
02700 Kauniainen,
Finland
http://personal.eunet.fi/pp/halo/
Judges' Comments:
To build: (You will need X11 header files and libraries installed to
build this program)
make jarijyrki
To run: (You will need a system capable of displaying the results of
X Window programs)
./jarijyrki < sheet1.info > myedits.info
This entry is one of those that makes you wonder why some commercial
software needs tens to hundreds of megabytes to install! This entry
does not simply do the basics, it includes graphing features. All this
program needs now is a flight simulator!
Selected Author's Comments:
1. OVERVIEW
This program is an X-Windows based spreadsheet program.
The main functions it supports are:
* Text cells
* Numeric cells
* Arithmetic operations: + - * /
* Pie charts
* Histograms
* Cell editing
* Formula line
* Dynamic recalculation
* Error detection
* Recursion detection
* Movement within the spreadsheet with cursor keys
* Movement within the spreadsheet with mouse
* Scrolling
* Loading and saving spreadsheets
* Visual style configuration
2. USAGE INSTRUCTIONS
2.1. Quick Guide
Starting: ./jarijyrki < sheet1.info > myedits.info
Stopping: Esc
Movement: Click mouse or cursor keys
Editing: Currently selected cell is always in 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 ... An @
Histograms: A1 A2 A3 ... An !
2.2. Starting and Loading Spreadsheets
To start the spreadsheet program with an existing
spreadsheet, use the following command line:
./jarijyrki < sheet1.info
The file sheet1.info 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 < sheet1.info > 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, sheet1.info, 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 cursor keys to move left, right, up, and down among the cells.
[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.] You may also click the mouse on a cell to cause it
to be activated as the current one.
Going beyond the borders of the window results in scrolling
the current view. It is not possible to go up from 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. Formula
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 calculated the sum of the cells A1 and A2, and then
multiplied 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 one. 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 slice 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 in 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 four first
ones define the movement operations and the latter two ones
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
cursor 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 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 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 have come 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 or does not "i(=)" do and why?
4. WARNINGS AND CAVEATS
4.1. X11 Paths in Compilation
The given build file may have to be edited to insert correct
library and include file path names.
4.2. Font Sizes
We've tested the program with 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 may 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:
(a) Horizontal (alphabet) dimension handling will always be
A to Z regardless of the actual allocated memory area.
(b) Any change in the dimension parameter renders existing
spreadsheet files unsuitable.
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
may 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.