Array tools

[arthuro555]

Describe the extension

This adds a lot of of utility functions for working with arrays. It adds the following types of possibilities:

• Combining arrays (concatenate into new array, append all children to another array)
• Finding a value in an array (find index expression, contains condition)
• Reversing arrays
• Get a portion of an array (slice)
• Add and remove lots of children at specific indices at once (fill, splice, shift, pop, add at index)
• Randomness (shuffle children, get a random child)
• Mathematical operations using arrays (sum of all numbers, biggest/smallest number, average number, median number)
• Sort numbers in an array
• String inter-operation (split string into array, join array array children to string)

Checklist

• [X] Extension has a proper name and description.
• [X] Extension has tags (for example: "platform, brick, breakable").
• [X] All behaviors have a description.
• [X] All functions (actions, conditions, expressions) have descriptions and proper sentences.
• [X] I've followed the best practices listed on http://wiki.compilgames.net/doku.php/gdevelop5/extensions/best-practices
• [X] I confirm that this extension can be intergrated to this GitHub repository, distributed and MIT licensed.

Example

I don't have an example file, but I have (arguably) better. Here are some unit tests in a GDevelop project file: arraytools-unit-tests.zip

Extension file

ArrayTools.zip

[Bouh]

Verification list

• [x] Contains
• [x] Index Of
• [ ] Last Index Of
• [x] Flatten
• [ ] Splice
• [ ] Slice
• [x] Sum
• [ ] Shuffle
• [ ] Reverse
• [ ] Sort
• [x] Min
• [x] Max For min and max there is different way to do the job, idk which one is more performant

  
  Math.min.apply(Math, arr.map(variable => variable.getAsNumber()));

// Prefered solution: Math.min.apply(null, arr.map(variable => variable.getAsNumber()));

Math.min(...arr.map(variable => variable.getAsNumber()));

- [ ] Join
- [ ] Split
- [ ] Mean
- [ ] Median
- [ ] Get Random Child
- [ ] Fill
- [ ] Concat
- [ ] Append To
- [ ] Pop
- [ ] Shift
- [ ] Insert variable at

I recommend to remove private functions, used for create sections in functions list. It's fine for review and testing it only.

[tristanbob]

In the ShadowClones extension, my current logic is this:

0) Assume N = number of shadow clones * frames between clones 1) Copy all child variables from ObjectHistory.N to ObjectHistory.N+1 (this can result in copying thousands of variables every frame) 2) Create a new child variable at ObjectHistory.1 based on current values of sprite

I think for this logic to work with arrays, I need to use "unshift: Adds new elements to the beginning of an array".

0) Assume N = number of shadow clones * frames between clones 1) Unshift array to create new child based on current values of sprite 2) Pop array until array length = N (this will remove old data that we don't need any longer)

Using arrays should be MUCH more performant compared to copying values of all child variables.

TLDR: Can you please add "unshift"?

[arthuro555]

I intentionally didn't add unshift as I think it may bloat a bit too much considering the insert variable at with index parameter 0 is equivalent

[tristanbob]

I intentionally didn't add unshift as I think it may bloat a bit too much considering the insert variable at with index parameter 0 is equivalent

Ah, yes, that sounds like it is what I need (and more flexible for other uses). Thanks!

[4ian]

Math.min.apply(Math, arr.map(variable => variable.getAsNumber())); // Prefered solution: Math.min.apply(null, arr.map(variable => variable.getAsNumber())); Math.min(...arr.map(variable => variable.getAsNumber()));

Remember that in the context of JavaScript written for games, it's actually better not to use map/filter as they will create new arrays in memory, and will create pressure on the garbage collector. Using apply with an array is also a risk to crash/slow down terribly the JS engine because you're calling a function with as much parameters as the the array length... imagine if this is an array of 1000 or 10000 objects - JS engines are not ready for these and will deoptimize (at best).

Instead, just do a for loop and keep the minimum or maximum value. It's the most efficient, no slow down, 0 memory allocations, and probably optimized by JS engines.

[arthuro555]

Instead, just do a for loop and keep the minimum or maximum value. It's the most efficient, no slow down, 0 memory allocations, and probably optimized by JS engines.

Done, here is the modified extension and unit tests: ArrayTools.zip arraytools-unit-tests.zip

[Bouh]

Something interesting during my review, the long description is not show for Boolean type!

[arthuro555]

I was wondering, should an expression that builds an array out of the key of a structure (Object.keys) be part of this extension or of a "Structure tools" extension?

[4ian]

Good question.. Might be the same extension but should this be renamed to "Collection variable tools" then?

[arthuro555]

🤔 It's ok for me, but if it becomes tools for collections generally it might grow huge quickly, while separating in multiple extensions would allow to have smaller more maintainable packages.

[4ian]

I honestly don't have a strong feeling on this, on the other hand it might be simpler for the user to just install one extension? But feel free to do a separate one if you prefer!

[tristanbob]

My preference is to consolidate extensions that are highly related, but like Florian said it is up to you.

For array functions, is there a reason they make sense as an extension versus provided by default in GDevelop?

[4ian]

For array functions, is there a reason they make sense as an extension versus provided by default in GDevelop?

One reason if any is that it's 1) faster to get these made as extensions now, so that we can try and use them as soon as the extension is ready and 2) safer, in the sense that if the interface (the conditions/actions names, parameters, etc...) are not perfect, we can fix that by releasing an update extension.

On the other hand, everything that is by default in GDevelop is considered to be there "forever", and any breaking change must be either avoided or automatically upgraded. As the article says, APIs, like diamonds, are forever.

This being said, it's also possible that we "graduate" the extension or part of it into a built-in GDevelop extension, after we have proved it's 1) well designed and 2) used by a number of games so large that it's better to have it not as an extension. Finally, all this discussion could maybe be avoided if in the future we push more extensions in the interface, and we could even suggest a set of "default extensions" to be used in new games :)

[tristanbob]

4ian thanks for the great answers to my questions.

Now for more questions:

Are you considering adding support for 2D arrays? This would help with mapping 2D grids. For instance, fog of war opacity values.... ;)

[arthuro555]

Arrays can already be 2D, a 2D array is just an array of arrays, and arrays can contain any variables including arrays.

[tristanbob]

(For the next update) Add a "unique" function (perhaps as a parameter on sort) that only keeps one instance per number.

Use case: I am using a secondary array to track the indexes of a primary array that need to be modified. This secondary array might contain the same value multiple times. However, I only want to apply the modification one time per value. With a unique function, I could do this.

[arthuro555]

I'm starting to collect ideas for the next update too. That sounds like a good idea. Some other ideas I had:

• create an array of structure keys
• remove all "falsely" values (0, "", "0", false, "false", "null"...)
• chunk array (chunk [1,2,3,4,5,6] by 3 it becomes [[1,2,3],[4,5,6]], by 2 it becomes [[1,2],[3,4],[5,6]])
• structure to pairs: {a:1,b:"yes"} => [["a", 1], ["b", "yes"]]
• convert pair back to structure
• create array with all items that are in both 2 input arrays([1,2] and [2,3] => [2])
• remove all values in array2 from array1 ([1,1,2,3,4] and [1,3] => [2,4])
• remove an array of indices ([1,2,3,4,5] and [0, 2] => [2,4,5])