Reproduce LaTeX's `\vec` for "i" and "j"

Questions
1

I’m aware of accent() and arrow() from this thread. However, when used in $accent(i)$ or $accent(j)$, the arrow replaces the dot instead of being over it.

A workaround that I found is to wrap with a box ($arrow(#box($i$))$), but I cannot systematically apply this method to smaller characters like “o”, because then the arrow is placed too high (as if the “o” were an “l” for example).

What other solutions do I have?

2

Hi there! Welcome to the Forum.
I created a custom function that should do what you are looking for:

#let my_vec = (letter) => {
  if (($j$, $i$).contains(letter)) {
    $arrow(#box(letter))$
  }
  else {
    $arrow(letter)$
  }
}
#my_vec($j$)
#my_vec($i$)
#my_vec($o$)

By the way, I tried to use

#show math.arrow: it => [Demonstration of it not working]

but it seems like it ignores the show rule, so I think it might not work with this math function or am I doing something wrong? :sweat_smile:

3

There’s a new parameter for math.accent, will be in next typst version I guess, that controls this. Add dotless parameter to `math.accent` by mkorje · Pull Request #5939 · typst/typst · GitHub

2 Likes
4

Looking at the output of this

#import "@preview/mitex:0.2.5": *
#import "@preview/m-jaxon:0.1.1": *

#text(16pt, render("\vec{j} j \vec{a} a", inline: true))

#mi("\vec{j} j \vec{a} a")

image

I guess that it’s just the current limitation of Typst, if there is no open issue about it at GitHub - typst/typst: A new markup-based typesetting system that is powerful and easy to learn., then you can open one.

5

Indeed.

$arrow(j) j arrow(a) a$

#set math.accent(dotless: false)

$arrow(j) j arrow(a) a$

image

2 Likes
6

You need this:

#show math.accent: it => {
  if it.accent != "\u{20d7}" { return it }
  repr(it)
}

See Accent Function – Typst Documentation and this.

1 Like
7

I didn’t know/remember you have to return the output in math mode. Thanks a lot for the correction/advice :+1:

8

You don’t have to return, you were using the wrong show rule selector.

1 Like
9

Oh, OK. It didn’t show an error message and the documentation says

$arrow(a) = accent(a, arrow)$

in the example, so I thought arrow should also be a math function. So are just the ones listed in the overview on the left of there documentation under “math” usable for this?

10

It’s because accent is the element function. I guess we can assume arrow is not since it does not have an entry in the docs.

bild

Are there non-element functions in the math docs? Yes, math.sans is an example.

1 Like
11

Thanks for your replies! I’ll wait for the next release then :slight_smile:

12

Thank you for the clarification. Do you think I should open an issue? I think the fact that it doesn’t throw an error and does nothing is a bit irritating. It should be possible to check, if the entered function is an element function, right?

13

I think it should have an issue if it doesn’t already have one. I can see in the typst app that the autocomplete knows that they are different kinds of entities

14

I opened an issue: add warning/error message for show-rules with non-element function · Issue #6141 · typst/typst · GitHub

15

I’ve left a comment add warning/error message for show-rules with non-element function · Issue #6141 · typst/typst · GitHub. In short, it’s a symbol with some funky function behavior, hence why show rule doesn’t throw an error.

This is actually a function, so the show rule with it does throw the error.