How can I set numbering for sub-equations?

Questions
,
1

How can I set numbering for sub-equations as follows?
image

2

Hello @shhuang!
You can take a look at the equate package.
The discussion about this feature is at Fine grained equation numbering control · Issue #380 · typst/typst · GitHub

3

Thanks!
I tried equate package and it worked. However, when I tried to use cross-reference it would override the format I set before.
The codes are:

show: equate.with(breakable: true, sub-numbering: true)
set math.equation(numbering: "(R1a)")
show ref: it => {
    let eq = math.equation
    let el = it.element
    if el != none and el.func() == eq {
      // Override equation references.
      numbering(
        el.numbering,
        ..counter(eq).at(el.location()),
      )
    } else {
      // Other references as usual.
      it
    }
  }

It looks great in the equation block:
image
But in the reference:
image
How can I change “Equation 5a” to “(R5a)”?

4

Hi,
the above show rule only handles build in equations you have to add a case for equations from the package:

#import "@preview/equate:0.2.1": *

#show: equate.with(breakable: true, sub-numbering: true)
#set math.equation(numbering: "(R1a)")
#show ref: it => {
  let eq = math.equation
  let el = it.element
  if el != none and el.func() == eq {
    // Normal equations
    numbering(el.numbering, ..counter(eq).at(el.location()),
    )
  } else if el.func() == figure and el.kind == eq {
    // Equate equations
    numbering(el.numbering, ..el.body.value)
  } else {
    // Rest
    it
  }
}

$
  a = b #<a>\
  b = c #<b>
$ <1>

See @1, @a and  @b

Another option would be to use a function instead of a numbering pattern string. It is more compact but less flexible.

#import "@preview/equate:0.2.1": *

#show: equate.with(breakable: true, sub-numbering: true)
#set math.equation(supplement: none)
#set math.equation(numbering: (..n) => numbering("(R1a)", ..n))

$
  a = b #<a>\
  b = c #<b>
$ <1>

See @1, @a and  @b
Result

test

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