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Advent I

2016-11-27, post № 148

art, haiku, poetry, #winter

First candle is lit,
Advent season is now here.
Charming wintertime.

Praiku

2016-11-19, post № 147

art, haiku, mathematics, poetry, programming, Python, #prime

While you have no primes,
While you would like to know them.
If, if you could print…

brainfuck

2016-11-05, post № 146

brainfuck, programming, Python, #esoteric, #interpreter, #minimalism

Usually, programming languages are designed to be efficient, understandable and usable. Their concepts are well thought-out, giving the programmer powerful tools to create their application.
Esoteric programming languages have a slightly different aim. Instead of focusing on the product, they focus on the programmer’s journey and try new approaches to building a program.
One well-known esoteric programming language is Urban Müller’s brainfuck. It is a Turing-complete programming language — meaning that it could with infinite memory do what a Turing machine can do —, which practices extreme minimalism. The language knows of only eight characters (<>+-[].,).
The language’s usage is very similar to a Turing machine. Starting the program, the pointer is at cell zero and can be moved left (<) or right (>) by one cell.
The cells’ values are all starting at 𝟢, but can be either increased (+) or decreased (-) by one. Because the cells can only store one unsigned byte, adding one to 𝟤𝟧𝟧 yields in 𝟢 and subtracting one from 𝟢 yields in 𝟤𝟧𝟧.
Also, a loop is possible by using square brackets. An open square bracket ([) starts a loop and a closed square bracket (]) ends a loop. When the end of a loop is reached, the interpreter will jump back to its start if and only if the currently selected cell’s value is 𝟢. [1]
The only way to communicate with the user is to print the currently selected cell’s ASCII character to the screen (.) and get a user input which will be stored in the currently selected cell as its ASCII value (,).

Because of its minimalistic design, writing an interpreter is not particularly hard. Listed below is the Python code of my interpreter, which I used to execute my own brainfuck “Hello World.” program (𝟣𝟣𝟪 characters).
Online interpreters include for example bf.doleczek.pl and sange.fi.

Useful Wikipedia articles include Esoteric Programming Language, Brainfuck and Turing Machine.

$ python brainfuck.py
Hello World.
Source code: brainfuck.py

Halloween MMXVI

2016-10-31, post № 145

art, poetry, #horror, #purple cube, #sea, #story

It is an icy autumn night, thick fog coats the barren land. I walk down the beach. No other human is visible. The water is still, only barely moving. After a while I come to the haven. To escape the eerie land, I get to my boat and sail away, leaving.
Looking back, the port’s lights shine through the fog. The world seems quiet, time has nearly stopped. I can hear myself breathing, my heart beating. I find relief in the loneliness on sea. The subtle waves make me fall into a deep sleep. For hours me and my little boat sail the ocean.
A hypnotizing melody wakes me up. At first gentle, with time louder. It seems like I was getting pulled towards it. Due to the still thick dog I only saw a silhouette of the song’s source. It was an enormous cube, floating on the water. As I got nearer, it started to glow dimly purple.
Fascinated by the strange object, I lost the feeling for my surroundings. The water beneath the cube bulged, drawing me into the center. My senses slowly started to fade. My whole body got paralyzed, I was not able to move. My heart beat more slowly, eventually stopping. My lifeless, rigid body sank down.
I suffered the same fate as hundreds before me, becoming a statue on the ocean floor.

99 Bottles of Beer

2016-10-22, post № 144

art, codegolf, poetry, programming, Pygame, #character-sparse code, #characters, #space-efficient, #StackExchange

I recently [1] found a five year old StackExchange thread talking about a programming challenge to recreate the marvelously imaginative lyrics of ‘99 Bottles of Beer’. The song goes as follows (whole lyrics can be viewed below).

99 bottles of beer on the wall, 99 bottles of beer.
Take one down and pass it around, 98 bottles of beer on the wall.
98 bottles of beer on the wall, 98 bottles of beer.
Take one down and pass it around, 97 bottles of beer on the wall.
97 bottles of beer on the wall, 97 bottles of beer.
Take one down and pass it around, 96 bottles of beer on the wall.
[…]
3 bottles of beer on the wall, 3 bottles of beer.
Take one down and pass it around, 2 bottles of beer on the wall.
2 bottles of beer on the wall, 2 bottles of beer.
Take one down and pass it around, 1 bottle of beer on the wall.
1 bottle of beer on the wall, 1 bottle of beer.
Go to the store and buy some more, 99 bottles of beer on the wall.

Of course, the real challenge is not to build a program that generates the lyrics but rather to do it with the least amount of characters [2]. To achieve this goal, I tried out various strategies, all written in Python.

The first strategy is to join a string generated by a for loop (𝟤𝟨𝟥 characters).

99-bottles-of-beer_d...-function.py; Python2, 264 bytes, 3 lines
a,b=" bottles of beer"," on the wall"
c=a.replace("s","")
print"\n".join([str(n)+a+b+", "+str(n)+a+"."+"\nTake one down and pass it around, "+str(n-1)+[a,c][n<3]+b+".\n"for n in range(99,1,-1)])+"\n1"+c+b+", 1"+c+".\nGo to the store and buy some more, 99"+a+b+"."

The second, less efficient strategy is to use a function and recursion (𝟤𝟩𝟦 characters).

99-bottles-of-beer_d...-function.py; Python2, 275 bytes, 8 lines
a,b=" bottles of beer"," on the wall"
c=a.replace("s","")
def f(n):
	s=""
	if n>1:
		s="%d"%n+a+b+", %d"%n+a+".\nTake one down and pass it around, "+str(n-1)+[c,a][n>2]+b+".\n\n"+f(n-1)
	return s
print f(99)+"1"+c+b+", 1"+c+".\nGo to the store and buy some more, 99"+a+b+"."

The third is a bit more character-efficient, using lambda functions and recursion (𝟤𝟩𝟢 characters).

99-bottles-of-beer_d...gy-lambda.py; Python2, 271 bytes, 6 lines
a="%d bottle%s of beer"
b=" on the wall"
c=["","s"]
f=lambda i:a%(i,c[i>1])+b+", "+a%(i,c[i>1])+".\nTake one down and pass it around, "+a%(i-1,c[i>2])+b+".\n\n"
F=lambda i:f(i)+F(i-1)if i>0 else ""
print F(99)[:-65]+"Go to the store and buy some more, "+a%(99,"s")+b+"."

The fourth, final and most space-efficient [3] strategy is to use a while loop (𝟤𝟧𝟢 characters).

99-bottles-of-beer_d...egy-while.py; Python2, 251 bytes, 7 lines
a="%d bottle%s of beer"
b=" on the wall"
c=a+b+", "+a+"."
i=99
s=""
while i>1:s+=c%((i,"s")*2);i-=1;s+="\nTake one down and pass it around, "+a%(i,["","s"][i>1])+b+".\n\n"
print s+c%(1,"",1,"")+"\nGo to the store and buy some more, "+a%(99,"s")+b+"."

Menger Sponge II

2016-10-08, post № 143

Processing 3, programming, Python, #3D, #fractal, #three dimensions, #three-D, #three-dimensional

In July of 2015 I published my Menger Sponge post. As I said there, the true Menger Sponge is a three-dimensional object, but due to the lack of 3D-integration in Pygame, I only showed one of the six cube’s faces. The two-dimensional fractal is officially called Sierpiński carpet while the three-dimensional object is really called a Menger sponge.
To achieve the three-dimensional cube, I used Processing 3 together with its Python Mode.
The actual fractal is colored with a pseudo-randomly chosen color. All its smaller cubes then get a slight color shift. The cube rotates slowly, with a different speed on each of the three axes.

Controls

  • ‘Space’will advance the cube’s fractalness,
  • ‘q’ will save an image of the current fractal’s state.
menger-sponge-ii-0.png
menger-sponge-ii-1.png
menger-sponge-ii-2.png
menger-sponge-ii-3.png
menger-sponge-ii-4.png
Source code: menger-sponge-ii.pyde

Microcounter

2016-09-24, post № 142

MicroPython, programming, Python 3, #micro, #microcontroller, #pyboard

Being a big fan of Python [1], I recently got a MicroPython Board.
MicroPython is a simple to use micro controller which runs Python 3. To put code onto it, you simple mount it as you would do with a USB flash drive, copy your main.py to it and restart your MicroPython.
As a simple “Hello world.”-program, I wrote this counting script. Every time you press the built-in [2] button, it counts up by one. Using the four built-in LEDs and binary number representation, this counter can count from 𝟢 to 𝟣𝟧 and then wraps back.

microcounter.gif
Source code: microcounter.py

J-Trix

2016-09-10, post № 141

curses, programming, Python, #animation, #bit, #bits, #falling bits, #hacker, #hacking, #Matrix, #screensaver

Recreating the famous falling bit effect from Matrix using python and curses.The individual bit strips are separate entities, falling to the bottom and then being moved up again with a different 𝑥 value. They also get a random speed between one and five deciseconds.

j-trix.gif
Source code: j-trix.py

Collatz Conjecture

2016-09-03, post № 140

mathematics, programming, Pygame, Python, #3n+1, #three n plus one

The Collatz conjecture states that every positive integer 𝑘 > 𝟢 will — if you iteratively set 𝑘 to 𝑓 (𝑘) — result in 𝟣 (function shown beneath).
The graph beneath shows the path length of numbers from 𝟣 to 𝟣𝟢 𝟢𝟢𝟢. In this range, 𝟨 𝟣𝟩𝟢 is the number with the most steps, 𝟤𝟨𝟣.

f(k)={\begin{cases}\frac{k}{2}&{\text{if }}k\mod 2=0\\3\cdot k+1&{\text{if }}k\mod 2=1\end{cases}}
collatz-conjecture.png
Source code: collatz-conjecture.py

Curses Cam

2016-08-27, post № 139

curses, programming, Pygame, Python, #camera, #color depth, #low resolution, #shell image, #.si, #text-based images

Normally a shell lets you input via a text command and outputs via a text message [1]. When using curses you can extend its capabilities and program for example games with limited graphics.
I wanted to go even further and built a Python script that — using Pygame’s camera module and curses — captures an image from an attached webcam (USB or built-in), transforms it and displays it on the shell.
Although both the resolution and the color depth are shrunk immensely, the resulting colored text on the shell often resembles the scene caught and has a nice visual effect.
There are two modes, camera and file viewer, which can be toggled by pressing ‘F1’. In camera mode you can see what the camera is seeing and snap a photo, which then will be saved to disk. In file viewer mode you can view the photos you took. The files will be saved in an out/ directory located in the current Python file’s directory. Saved photos have the file extension .si (“shell image”).
Unfortunately, Pygame’s camera module does neither work on Mac OS X nor on Windows. Thus this program is only properly usable under Linux [2] systems. You obviously also need a webcam or else you will not be able to take a picture.

Controls

  • ‘F1’ switches between camera and file viewer mode,
  • ‘Space’ saves the current photo as a .si file (only in camera mode),
  • Left or down arrow key decreases current file’s id (only in file viewer mode),
  • Right or up arrow key increases current file’s id (only in file viewer mode).
curses-cam_blinky.png
curses-cam_graffiti.png
curses-cam_hand-1.png
Source code: curses-cam.py

Jetris CE

2016-08-20, post № 138

curses, games, programming, Python, #bag, #bag method, #Tetris

This game’s challenge is
to arrange the falling blocks.
Stay alive forever.

Jetris Console Edition is my second Tetris clone (see Jetris for the first one). It is programmed in Python and uses the curses module to display all its graphics on the shell.
Despite it running purely on the shell, I managed to eliminate any noticeable graphics update bugs. Furthermore the code to clear lines differs immensely from Jetris and actually works properly.
To enhance gameplay I implemented the so-called bag method. Instead of choosing pieces at random, a bag gets filled with all seven possible pieces. Each time you get a new piece, that piece gets randomly chosen out of the bag. If the bag is empty, it gets refilled. That way it is ensured that there will be no more than twelve pieces between two identical pieces (worst-case scenario). Also there will no more than four ‘S’ or ‘Z’ pieces in a row which makes the game fairer.
The pieces initially fall at one pps (pixel per second) and the game runs at twelve tps (ticks per seconds). Every ten cleared lines the speed increases by one tick or one twelfth of a second until it stays at the minimum speed, one twelfth of a second. [1]
The game’s clock is handled by a thread and graphics updates are made when they are needed (there are no fps).
To achieve the pieces blocky look I used two spaces and a color pair whose background color is the piece’s color. On the shell two fully filled characters look like a square.
You also have the option to change your key bindings — which get saved on disk —, pause the game and there is a high score list — which also gets saved on disk. The files are located where the Python code file resides.

jetris-ce-1.png
jetris-ce-2.png
jetris-ce-4.png
Source code: jetris-ce.py