Make auto subscript 2 more general

[kiryph]

The suggested snippet by G. Castel

  s({
    trig = "([%a])_(%d%d)",
    name = "auto subscript 2",
  }, {
    f(function(_, snip)
      return string.format("%s_{%s}", snip.captures[1], snip.captures[2])
    end, {}),
    i(0),
  }),

does not work when using letters in indices such as a_ij and is constrained that only a single leading letter is allowed, e.g. when using greek letters \alpha_12, the snippet is also not triggered.

My snippet definition looks like

        s({
          trig = "_(%w%w)",
          name = "auto subscript 3",
          regTrig=true,
          wordTrig=false,
          snippetType="autosnippet",
        }, {
          f(function(_, snip)
            return string.format("_{%s", snip.captures[1])
          end, {}),
          i(1),
          t("}"),
          i(0),
        }, {condition = is_math}),

It is not yet battle tested. If there is a good reason why this is a bad idea, I am happy to hear it.

[iurimateus]

Thanks. Seems fine at a first glance, I'll try it out.

[iurimateus]

Any reason for setting i(1) inside the brackets? That would require you to move the cursor after.

It might be better to keep it outside. I assume on more complex subscripts you'd type __ to achieve _{|}.

Also, you've set wordTrig to false. What's the reasoning there, given that the other ones are in math_wRA? I ask because it's probably some case that I'm missing.

[kiryph]

Any reason for setting i(1) inside the brackets? That would require you to move the cursor after.

It might be better to keep it outside. I assume on more complex subscripts you'd type __ to achieve _{|}.

I like the behaviour that expr_%w%w| is expanded to expr_{%w%w|} and I can keep adding to the subscript if it is the case or jump outside when I finished with the subscript. But I do not want to think about how many letters I will type before I type.
When I remove i(1) it is assumed that expr_%w%w| remains a two letter subscript which is not necessarily the case. Just one example: the Levi-Civita symbol for d=3 is often written as \epsilon_{ijk}. This subscript does not feel complicated. It is just a three letter subscript instead of two. So I want to type it identically to a two letter subscript.

I also find the symbol _ more difficult to type. I added a personal snippet ,, (two commas) which is expanded to _.

Also, you've set wordTrig to false. What's the reasoning there, given that the other ones are in math_wRA? I ask because it's probably some case that I'm missing.

The definition of wordTrig is

- `wordTrig`: boolean, if true, the snippet is only expanded if the word
   (`[%w_]+`) before the cursor matches the trigger entirely.

Consider follwoing two different cases

1. \alpha_ij| here we could define the snippet as

        s({
          trig = "([%w_])+_(%w%w)",
          name = "auto subscript 3",
          regTrig=true,
          wordTrig=true,
          snippetType="autosnippet",
          priority=100,
        }, {
          f(function(_, snip)
            return string.format("%s_{%s", snip.captures[1], snip.captures[2])
          end, {}),
          i(1),
          t("}"),
          i(0),
        }, {condition = is_math}),

2. \vec{a}_ij|: here the pattern before the underscore (curly brace) is not at least one of [%w_]+ (the + quantifier) which makes the snippet to not trigger.