Converting Coding Challenge 'Self-avoiding Walk Backtracing' From ...

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p5.js Coding Questions psamead February 8, 2022, 7:34pm 1 Hi my friends, I am trying to learn coding challenge Self-avoiding walk backtracing from Denial’s video 26:40 ; And converting the P5.js code to processing(java) code. But my code seems it is struggling on getting the array right and null pointer. Can anyone help me to figure out the problem? GoToLoop February 8, 2022, 7:59pm 2 website/CodingChallenges/CC_162_self_avoiding_walk/backtracking at main ·...main/CodingChallenges/CC_162_self_avoiding_walk/backtrackingThe train engine powering the Coding Train website - website/CodingChallenges/CC_162_self_avoiding_walk/backtracking at main · CodingTrain/websitep5.js Web EditorA web editor for p5.js, a JavaScript library with the goal of making coding accessible to artists, designers, educators, and beginners. psamead February 8, 2022, 8:05pm 3 Hi @GoToLoop , Thanks for the reply! I have read the p5js version, but I can not figure out to convert it to processing code. I definately make some mistakes, but I can not figure them out. I wonder if someone can help to change it to processing java. GoToLoop February 9, 2022, 5:23am 4

I definitely made some mistakes, but I cannot figure them out.

In the original p5js version validOptions is a function which returns an array w/ 4 instances of Step:CodingTrain/website-archive/blob/main/CodingChallenges/CC_162_self_avoiding_walk/backtracking/spot.js#L21-L23

function allOptions() {

return [new Step(1, 0), new Step(-1, 0), new Step(0, 1), new Step(0, -1)];

}

But in your converted Java Mode version it is just an array not a function: Step[] allOptions = { new Step(1, 0), new Step(-1, 0), new Step(0, 1), new Step(0, -1) }; Also your attempt of emulating method Array::pop():CodingTrain/website-archive/blob/main/CodingChallenges/CC_162_self_avoiding_walk/backtracking/sketch.js#L56-L61

spot = spot.nextSpot();

if (!spot) {

let stuck = path.pop();

stuck.clear();

spot = path[path.length - 1];

} else {

Using Java’s List::remove() mixing w/ loops doesn’t seem to be working.BtW, I’ve ended up making my own conversion attempt and posted it online:1 Like GoToLoop February 9, 2022, 11:02am 5 Another version, this time named “Self Avoiding Walk II”, which implements a more aggressive backtracking based on the age of each Spot inside container path, so it has a better chance to unstuck itself:1 Like psamead February 9, 2022, 7:19pm 6 Hi @GoToLoop , Thanks for your replay and help. Your code is absolutely so much help and it is incrediable. And the openprocessing web editor is brilliant and it can declare static method with in, my current process IDE can not, except adding .java files. I don’t know much about javascript and am quite newbie, so as you point out my code drops some important idea of the original code on the conversion. With your advice and help, I figure out my problem

In the original p5js version validOptions is a function which returns an array w/ 4 instances of Step:

website-archive/CodingChallenges/CC_162_self_avoiding_walk/backtracking/spot.js at main · CodingTrain/website-archive · GitHub

But in your converted Java Mode version it is just an array not a function:

psamead:

> Step[] allOptions = { new Step(1, 0), new Step(-1, 0), new Step(0, 1), new Step(0, -1) }; > ```

And I borrowed your codeMy one is finally working, but it seems it will be stuck at some point quite long

it definately has other problems

psamead February 9, 2022, 7:26pm 7

rows >> 1

cols >> 1

btw what does this kind of expression mean? GoToLoop February 9, 2022, 7:34pm 8

BtW, what does this kind of expression mean?

The bitwise right shift operator moves all bits of a value ‘x’ times:>> (right shift) / ReferenceShifts bits to the right. The number to the left of the operator is shifted the number of places specified by the number to the right. Each shift to the right halves the number, therefore each right s…Each right shifting halves the value; so >> 1 is equivalent to / 2, >> 2 is / 4, and so on.The advantage of using the operator >> in place of / is that the former guarantees the result is always a whole number (truncated division) when the code is transpiled to run on the web from Java (Processing library) to JS (Pjs library).1 Like GoToLoop February 9, 2022, 7:58pm 9

And the OpenProcessing.org web editor is brilliant and it can declare static methods within; my current Processing IDE cannot, except by adding .java files.

I’ve coded everything in Processing IDE (PDE) version 3.5.4.So if you click the download icon from my online sketch and transfer those files to the offline PDE it should just run.Inside “.pde” files all classes we create are nested.In order to have static methods inside a nested class its class has to be declared static as well.On the other hand, top-level classes inside “.java” files are naturally static already.1 Like psamead February 10, 2022, 5:25pm 10 Thanks for the reference link, much appreciated psamead February 10, 2022, 5:32pm 11 sorry my mistake, I should say mix use of the static and non-static in the same class

thanks for this Chrisir February 10, 2022, 8:16pm 12 I got a question.I understand that the backtracking algorithm is recursive.In Java processing a recursive function wouldn’t update the screen throughout. How come it is updated here?Is it that you can update the screen throughout in p5 or is it just not really recursive? GoToLoop February 10, 2022, 9:03pm 13

I understand that the backtracking algorithm is recursive.

The approach taken by Daniel Shiffman in his Coding Challenge #162 YouTube video isn’t recursive.In my 1st version of it (“Self Avoiding Walk I”), the main algorithm happens here:As you can see, function getNextSpot() never calls itself as we woulda expected from a recursive 1.The way it works is like a stack, pushing & popping from the container’s tail index:

Method Spot::nextSpot() attempts to find a valid non-visited Spot from within array grid[][].

If successful, that found Spot is add() to path’s tail; and its Spot::visited state becomes true.

Otherwise, the previous Spot is remove() from path’s tail and its state is reset by calling method Spot::clear(); and then variable spot is updated to point to the now current Spot tail:

Is it that you can update the screen throughout in p5…

I believe callback draw() needs to finish before p5js sketch’s canvas is updated.1 Like Chrisir February 21, 2022, 4:02pm 14 Thank you so much for this good explanation!

GoToLoop February 22, 2022, 1:48pm 15 Decided to convert my sketch to Python Mode too:

“Self_Avoiding_Walk_II.pyde”:“functions.py”:“spot.py”:“step.py”:1 Like psamead February 22, 2022, 4:28pm 16 This is brilliant !!! psamead March 3, 2022, 5:25pm 17 Hi @GoToLoopI wonder if this one

removals += removed? 1 : -removals;

is equivalent

if (removed) { removals += 1;} else { removals -= 1; }

Chrisir March 3, 2022, 5:28pm 18

removed? 1 : -removals;

you can test it yourself.My guess2 Likes GoToLoop March 10, 2022, 12:57am 19

I’m back w/ another “Self Avoiding Walk II” conversion.

This time I’m using the CoffeeScript language which directly transpiles to JavaScript.

Processing 2 used to have a CoffeeScript Mode a long time ago and I’ve ended up learning it.

When I later decided to learn Python Mode to help folks here I’ve relied on my previous CoffeeScript knowledge b/c they have similar syntax.

The old CoffeeScript Mode relied on the Pjs library in order to run its transpiled sketch on the web.

Which by the way is the same lib that transpiles a Java Mode sketch to JS.

But I also wanted to use p5js & even q5js to run my latest conversion.

So why not make the new CoffeeScript sketch compatible w/ all those 3 libraries?

That’s exactly what I did! Each time the sketch is refreshed it randomly picks 1 of the 3 libs:

Click here to download the full app project. Also go to link below to view it fullscreen:

https://Self-Avoiding-Walk-II-CoffeeScript.Glitch.me

2 Likes GoToLoop March 23, 2022, 5:54pm 20 Well I couldn’t stop! I’ve found out a new language, RapydScript:GitHub - atsepkov/RapydScript: Python-inspired, decluttered JavaScriptPython-inspired, decluttered JavaScript. Contribute to atsepkov/RapydScript development by creating an account on GitHub. In the same vein as CoffeeScript is inspired by Ruby, RapydScript is inspired by Python.It’s the same “Self Avoiding Walk II” CoffeeScript multi-flavor sketch, but now converted to RapydScript:You can click here to download the full sketch so you can edit & run it somewhere else. And go to link below to view it fullscreen: