Different alignment for top and bot

[cu1ch3n]

Description

MWE:

$1 + top + 1$ \
$1 + bot + 1$

Reproduction URL

https://typst.app/project/rK-1vDa1XN7tJsfp_cQkAN

Operating system

Web app

Typst version

• I am using the latest version of Typst

[Enivex]

This is not a bug,

https://www.unicode.org/Public/math/revision-15/MathClass-15.txt

U+22A4 (top) is of class "normal" while U+22A5 (bot) is of class "relation".

You can however force typst to consider it to be normal by using class("normal", bot)

$1 + top + 1$ \
$1 + class("normal",bot) + 1$

[chengluyu]

I think this is a wrong classification, because we have two similar symbols in Unicode: up tack ⊥ and perpendicular ⟂. Even though they look the same, their uses are completely different. The up tack is used in type theory to represent the bottom type, which is a type with no values. We should differentiate them in Typst, otherwise it would cause trouble for different usages.

[cu1ch3n]

It is weird to me. I think bot (\bot in LaTex, U+22A5 in Unicode) is normally a constant symbol, while the similar-looking perpendicular symbol (⟂, \perp in LaTeX, U+27C2 in Unicode) is a acutally binary relation symbol. See https://en.wikipedia.org/wiki/Up_tack .

In LaTex:

\begin{align*}
1 + \bot + 1 \\
1 + \top + 1 \\
1 + \perp + 1
\end{align*}

The result would be:

I think people would regard bot as the constant. Maybe we can covert it into normal class and keep perp as a binary relation?

[Enivex]

It may be weird to you, but I just sent you a link to the list of classifications from the Unicode consortium. It's not something typst came up with.

Good news is that it's very easy to redefine #let bot =$class("normal",bot)$

[cu1ch3n]

Thanks for the reply. But if I write $⊥$ instead of $bot$, the workaround doesn't work...

[cu1ch3n]

#show math.bot: bot should work

[cu1ch3n]

not sure if it is related: https://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references#cite_note-perp-31

⊥: Unicode only defines U+22A5 as the "up tack", and the Unicode symbol for "perpendicular" is U+27C2: the two symbols look similar, but are separate in Unicode. However, HTML uses U+22A5 as its "perpendicular" symbol: this is a discrepancy between HTML and Unicode. As well, the U+22A4 character (the "down tack" symbol) rendered in a browser such as Firefox 3.6 can match the font of either "up tack" or "perpendicular", but not both, depending on whether a fixed-width or a proportional font is used. When viewed in Firefox 3.6, the symbols rendered in the order U+22A5, U+22A4, U+27C2 in a proportional font: "⊥ ⊤ ⟂" and a fixed width one: ⊥ ⊤ ⟂, shows that the "down tack" has a similar look to U+22A5 (HTML's "perpendicular") in the first case but matches U+27C2 in the second. This exemplifies the difficulties of the semiotics involved in interpreting glyphs, symbols and characters generally.