Godot: Add Array.last()

[Zylann]

Currently, to get the last element of an array we have to write array[array.size()-1], which is a bit tedious given how many times this case happens.
Could we have an array.last() method like STL does with back()?

[felaugmar]

Hey, I'm able to do that, it's really simple.

But I have a doubt about the array files at /godot/core/array.h \ cpp;
Just by changing the files and modifying the /doc/base/classes.xml to match, the new "version" of my array will work?

I saw this is different from Custom modules that we 'bind' the methods, that's the why of my doubt.

Edit: We need to write some test case for the new implemented function?

[27thLiz]

@felaugmar no it won't be exposed to gdscript automatically, you still have to bind it.
The binding for array methods happens in core/variant_call.cpp specifically here and there.

[supaiku0]

Just for record, it should return null on an empty array right?
And while we are at it, please let's also consider a array.first() function.

[felaugmar]

@Hinsbart, thx, I'll see if I can figure out how the binding works (it seems a little complex) and if I can understand, I'll contribute with both functions.

@Zylann array.last()
@supaiku-o array.first()

[bojidar-bg]

Note that we support array[-1] syntax just fine, so this might be useless nowdays.

[Zylann]

@bojidar-bg oh! Brilliant, I didn't know that :)
that makes my request obsolete. Just, be careful about off-by-one coder errors :p

[Zylann]

Actually, I wonder if it's really coherent with the C++ side. I don't see access by negative index in Array and Vector, only error.

[felaugmar]

Well, I did the functions, it's working, but faulty and is not so simple as I thought.
I can't figure out how to bind with the Variant returning value directly and how to break in editor in case of _p->array.size() == 0.

Well, temporarily, I give up of editing the core, it's missing some knowledge for me to do this.
😢

[Zylann]

@felaugmar usually I think error checking is done with something like

ERR_FAIL_COND(size() == 0, "The array is empty");

[bojidar-bg]

Should this be closed, or you prefer it staying open?

[Zylann]

I don't mind if nobody else wants this, I use [-1] now in GDScript. I would eventually like to have it in C++ because I saw it's not there, but I don't really need it now.

[bojidar-bg]

Retagging for core then...

[Kazuo256]

I would like to try implementing this. From what I gather from @felaugmar's attempt, I have to:

1. Implement methods Array::front and Array::back in core/array.{h,cpp}
2. Raise an error if the array is empty
3. Update the bindings in core/variant_call.cpp
4. Update the documentation in doc/base/classes.xml
5. Write tests?

Is that correct?

[27thLiz]

@Kazuo256 yes :)

[Kazuo256]

Alright. I'll probably come back to ask some things when I get to the tests.

[Kazuo256]

I just noticed I actually wrote front/back, but the original proposal was first/last. Is there a preferred one? Or should I make aliases?

Besides this point, I've finished steps 1 through 4. Time for tests. Is there a guide or quick reference I can follow for this?

[vnen]

Godot does not have automated tests.

[Kazuo256]

OK. Then I only need to know which name to use.

[Zylann]

When I first wrote the issue I was not really bothering about the names, as long as they are meaningful. Front and back sound fine, it's like STL.
Thank you for working on this :)

[vnen]

Solved by #7149.