Animating the Quantum Drunkard’s Walk

A recent PPCG challenge titled The Quantum Drunkard’s Walk was about a tiny drunken person for which quantum mechanics apply and who — being drunk — will randomly walk in one of the four cardinal directions each step they take.
As they experience the strange world of quanta, they can simultaneously take every path at once and their paths influence each other. The challenge then asked to output all possible positions the quantum drunkard could occupy, all paths they could take in ASCII representation.

The question also states this problem’s equivalence to a cellular automaton, when one removes the story boilerplate.
Cells in this cellular automaton are square and can occupy one of three states: empty, awake or sleeping. Each iteration, all cells change according to three rules.

  • An empty cell wakes up iff there is exactly one awake cell amongst its cardinal neighbours, else it stays empty.
  • An awake cell goes to sleep.
  • A sleeping cell continues to sleep.

Being code golf, the aim was to come up with a minimally sized source code; my attempt required 214 bytes and prints a nested array containing one-length strings (characters), as this output method is cheaper than concatenating all characters to one string.

python -rmi 200
python -rmi 200

However, one user took the challenge idea a bit further and created an animated gif showing the walk’s, or cellular automaton’s, progression over time with an increasing number of iterations. My Python program shown in this post does exactly that, generating an animated gif showing the automaton’s progression. I even implemented rainbow support, possibly improving the automaton’s visual appearance.
Python source code can be downloaded and seen below.

I use the Python Imaging Library to produce all frames and use a shell call to let ImageMagick convert all frames to an animated gif. Animation parameters are taken via shell arguments, a full list of features follows (also available via the -h flag).

  • --iterations N Number of iterations (initial frame not counted)
  • --colorempty C Empty cell color (#rrggbb)
  • --colorawake C Awake cell color (#rrggbb)
  • --colorsleeping C Sleeping cell color (#rrggbb)
  • --rainbow Use rainbow colors (overrides color settings)
  • --scale N Cell square pixel size
  • --convert Execute ImageMagick’s convert command
  • --delay N Delay between frames in output image.
  • --loop N Gif loops (0 means for indefinite looping)
  • --keepfiles Do not delete files when converting
python -s 25 -md 50
python -s 25 -md 50

# Python 2.7 code; Jonathan Frech; 1st of December 2017

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Generic C / Python Polyglot

A polyglot — coming from the Greek words πολύς (many) and γλώττα (tongue) — is a piece of source code which can run in multiple languages, often performing language-dependent tasks.
Even though such a source code’s feature may not seem particularily useful or possible with certain language combinations, trying to bend not one but multiple language’s syntactic rules and overall behavior is still interesting.

An example of a rather simple polyglot would be a Python 2 / Python 3 polyglot — if one counts those as two separate languages. Because of their enormous similarities, one can pick out differences and use those to determine which language runs the source code.

if 1/2>0:print("Python 3")
else:print("Python 2")

Utilizing Python’s version difference regarding integer division and real division is one of the most common ways to tell them apart, as it can also be used to only control a specific part of a program instead of having to write two nearly identical programs (increases the program’s style and cuts on bytes — an important consideration if one golfs a polyglot).

However, polyglots combining languages that are not as similar as Python 2 and Python 3 require more effort. The following is a general Python 2 / C polyglot, meaning that nearly all C and Python 2 programs can be mixed using this template (there are a few rules both languages need to abide which will come apparent later).

#define _\
#define _"""
print"Python 2"

In the above code, main(){printf("C");} can be nearly any C code and print"Python 2" can be nearly any Python 2 code.
Language determination is exclusively done via syntax. A C compiler sees a #define statement and a line continuation \, another two #define statements with a block comment in between and actual compilable C source code (view first emphasis).
Python, on the other hand, treats all octothorps, #, as comments, ignoring the line continuation, and triple-quoted strings, """...""", as strings rather than statements and thus only sees the Python code (view second emphasis).

My first ever polyglot used this exact syntactical language differentiation and solved a task titled Life and Death of Trees (link to my answer).