Lack of ⊻ U+22BB

[uwni]

Currently, in Typst, the xor symbol is mapped to ⊕ (U+2295, plus.o). I propose remapping xor to ⊻ (U+22BB, XOR in Unicode), which is currently not encoded in Typst.

Rationale

Semantic Consistency: Typst uses ∨ (or, U+2228) for the logical OR operation. In mathematical logic, if "OR" is represented by the "vee" symbol (∨), its exclusive counterpart "XOR" is standardly represented by the "vee with bar" symbol (⊻).

Unicode Alignment: The Unicode character U+22BB is explicitly named "XOR". Using this mapping aligns Typst with international standards.

Ambiguity Resolution: Currently, xor is an alias for plus.o (⊕). While ⊕ is sometimes used for XOR (especially when "OR" is represented as +), it primarily means "circled plus" or "direct sum." Decoupling these allows:

xor → ⊻ (Logical exclusive OR)

plus.o → ⊕ (Mathematical circled plus)

[MDLC01]

I personally have never seen xor represented as ⊻, but I've seen it denoted with ⊕; probably because exclusive or is not often used in logic, when the ∨ and ∧ symbols are predominant.

I also don't think we have any reason to align our human-friendly names with Unicode's. Indeed, Unicode has made multiple naming mistakes in the past, and their names aren't always human-friendly. They are meant to be descriptive (in combination with the representative glyph, and additional information in the Core Spec).

However, I agree with your proposed change because, as you noted, ⊕ is already present in Codex as plus.o, and xor being ⊻ would be consistent with or being ∨. An alternative is or.exclusive.

In terms of implementation, if we go with your proposal, this would have to be done in two steps: first, deprecating xor in the next release. Then, un-deprecating it and changing it to ⊻ in a future release.

This could also be the occasion to add nand (or and.not) as a name for ⊼.

[T0mstone]

How about using xor.alt?

[Enivex]

There's a ton of symbols used for xor from various authors. Trying to have a semantic name for all of them wouldn't really be possible.

I think it makes most sense to stick with the status quo of ⊕. Those using another symbol can easily override it.

[dccsillag]

+1 for keeping the current xor (as far as I'm aware it's by far the more common form of xor) and add ⊻ as xor.alt (so that we have it).

[Enivex]

+1 for keeping the current xor (as far as I'm aware it's by far the more common form of xor) and add ⊻ as xor.alt (so that we have it).

There's 7 alternative symbols listed on https://en.wikipedia.org/wiki/Exclusive_or

I don't think ⊻ needs to be anything more than a variant of "or".

[dccsillag]

I don't think ⊻ needs to be anything more than a variant of "or".

Sure, I'm fine with that. Maybe something like or.underbar? I feel like the previously-proposed or.exclusive being different from xor might be confusing, besides not really solving the "too many options for xor" problem.

[Enivex]

We should probably name the bottom-accents first.

[MDLC01]

More symbols with decorations such as bars are listed in Section 10. Mathematical Symbols with Decorations of the Symbol List for sym document. For posterity, I'll copy below what I wrote at the top of this section.

There are three main places a decoration may appear relative to a base symbol: above, below, or inside. We propose that each decoration has its own modifier (e.g., .dot, .ast). By default, the decoration is placed inside the symbol, but an additional modifier can be added to specify a different position.

The exact modifiers that should be used to determine whether a decoration is placed above or below the base symbol are not definitive yet. In this section, we use .above and .below. Other options include .over and .under. For prior discussion, see typst/typst#4939 (comment).

Additionally, I wrote the following in section 10.3. Bars:

The current modifier for decorative bars is .bar, such as for ⦱ emptyset.bar. However, .bar is already used in a different way for ↦ arrow.bar, and | bar is an unrelated symbol. This may indicate that some of them should be renamed.

For .bar, unless explicitly noted, the default when both .above and .below exist should be .above.

We have a single precedent for symbols with bars: emptyset.bar/nothing.bar, added in typst/typst#4826.

In summary, this is part of a larger work to find a good naming convention for symbols with decorations that can appear on various places.