Add logical XOR to GDScript

[JeffVenancius]

This is an incomplete implementation of a logical XOR.
I've used 'but' and '^^' as keyword and aliases. It works but only if you do one comparison at a time.
There's no highlighting for 'but' and there's no auto-completion.
I'll keep working on it, still.

• Bugsquad edit: This closes Add XOR operator to GDScript godot-proposals#3849.

[MewPurPur]

You have not linked a proposal suggesting this or defended your case. For booleans, != does the same as XOR afaik.

[Calinou]

You have not linked a proposal suggesting this or defended your case.

There's already an open proposal: godotengine/godot-proposals#3849

It hasn't garnered much community support, and the original idea was already rejected more than once.

[dalexeev]

I've used 'but' and '^^' as keyword and aliases.

Why but? I think xor is more familiar and expected.

[JeffVenancius]

I've used 'but' and '^^' as keyword and aliases.

Why but? I think xor is more familiar and expected.

I've choosed "^^" because I thought it would make sense aliases-wise.
You know, as logical and is "&&" and logical or is "||".
I don't mind changing it to XOR, if it's prefered or even put it as one more alias for it.

[JeffVenancius]

You have not linked a proposal suggesting this or defended your case. For booleans, != does the same as XOR afaik.

Sorry about that, I'll look into it!

It's not the same thing, though, I mean...

var foo = 0
var bar = 1

if foo == 0 or bar == 1:
    pass # will execute even if you don't want to.

if foo == 0 and bar != 1 or foo != 0 and bar == 1:
    pass # will not not execute. 

if foo == 0 and bar != 2 or foo != 2 and bar == 1:
    pass # will execute.

# My proposal shortens this into this one:
if foo == 0 but bar == 1:
    pass # you can read it left to right or right to left.

[0x0ACB]

You have not linked a proposal suggesting this or defended your case. For booleans, != does the same as XOR afaik.

Sorry about that, I'll look into it!

It's not the same thing, though, I mean...

var foo = 0
var bar = 1

if foo == 0 or bar == 1:
    pass # will execute even if you don't want to.

if foo == 0 and bar != 1 or foo != 0 and bar == 1:
    pass # will not not execute. 

if foo == 0 and bar != 2 or foo != 2 and bar == 1:
    pass # will execute.

# My proposal shortens this into this one:
if foo == 0 but bar == 1:
    pass # you can read it left to right or right to left.

if foo != bar:
  pass # will execute

shortened this even more for you ^^. For booleans != is equivalent to xor. Or if I am misunderstanding your example and the booleans are supposed to be the foo == 0 part:

if (foo == 0) != (bar == 1)

Truth table for !=

a	b	res
false	false	false
false	true	true
true	false	true
true	true	false

Truth table for xor

a	b	res
false	false	false
false	true	true
true	false	true
true	true	false

[JeffVenancius]

You have not linked a proposal suggesting this or defended your case. For booleans, != does the same as XOR afaik.

Sorry about that, I'll look into it!
It's not the same thing, though, I mean...

var foo = 0
var bar = 1

if foo == 0 or bar == 1:
    pass # will execute even if you don't want to.

if foo == 0 and bar != 1 or foo != 0 and bar == 1:
    pass # will not not execute. 

if foo == 0 and bar != 2 or foo != 2 and bar == 1:
    pass # will execute.

# My proposal shortens this into this one:
if foo == 0 but bar == 1:
    pass # you can read it left to right or right to left.

if foo != bar:
  pass # will execute

shortened this even more for you ^^. For booleans != is equivalent to xor. Or if I am misunderstanding your example and the booleans are supposed to be the foo == 0 part:

if (foo == 0) != (bar == 1)

Truth table for !=
a b res
false false false
false true true
true false true
true true false

Truth table for xor
a b res
false false false
false true true
true false true
true true false

You're right!
Actually, the last implementation I've made is basically this, but with a different precedence - which means you won't need parenthesis, here:

if (foo == 0) != (bar == 1) # usual.

if foo == 0 but bar == 1 # my implementation. The "but" is checked after the other ones.

[dalexeev]

There's no highlighting for 'but' and there's no auto-completion.

For autocompletion you need to add the keyword here:

godot/modules/gdscript/gdscript_editor.cpp

Lines 1244 to 1248 in e0e93ce

	static const char *_keywords_with_space[] = {
	"and", "not", "or", "in", "as", "class", "class_name", "extends", "is", "func", "signal", "await",
	"const", "enum", "static", "var", "if", "elif", "else", "for", "match", "while",
	nullptr
	};

[JeffVenancius]

I think checks are not working because of documentation but I don't know what to do, atleast not right now.
That's the only thing left, though.

[dalexeev]

I think checks are not working because of documentation but I don't know what to do, atleast not right now.

You can use the bin/<godot executable> --doctool command to regenerate the documentation. But in this case the error is different:

[dalexeev]

I have added some changes in addition to yours. You can apply the patch with git apply or git am. Please note that this PR should have one commit (not multiple). If you want, you can add me as a co-author, but it doesn't really matter to me.

xor_review.patch.txt

P.S. Sorry for the long reply, I was sick and couldn't review your PR.

[JeffVenancius]

I have added some changes in addition to yours. You can apply the patch with git apply or git am. Please note that this PR should have one commit (not multiple). If you want, you can add me as a co-author, but it doesn't really matter to me.

xor_review.patch.txt

P.S. Sorry for the long reply, I was sick and couldn't review your PR.

That's OK, thank you for your patience and help!

[dalexeev]

Looks good to me!

[adamscott]

@JeffVenancius If you could rebase your PR, we could merge it soon. :)

[vnen]

@JeffVenancius If you could rebase your PR, we could merge it soon. :)

Well, perhaps we should discuss this with the whole GDScript team, given the proposals for this are controversial.

Even so, this PR cannot be merged as is because it only adds the keyword to the language, it does not implement the actual operator at runtime. It would also be nice to add tests, to verify the implementation itself.

[shenkes]

FWIW, this PR seems related to the boolean operators section of the style guide where it is encouraged to use AND, OR, and NOT instead of &&, ||, and !