Re: Fenced Div to ConTeXt Environment (was: Markdown Fenced Div to LaTeX Environment)

[Bastien DUMONT <bastien.dumont-VwIFZPTo/vqsTnJN9+BGXg@public.gmane.org>]

One possible solution:

```lua
ENV_CLASSES = { 'intro', 'question', 'solution' }

local function context(s)
  return pandoc.RawBlock('context', s)
end

local function get_env_class(elem)
if elem.classes then
  for i = 1, #elem.classes do
    for j = 1, #ENV_CLASSES do
      if elem.classes[i] == ENV_CLASSES[j] then return ENV_CLASSES[j] end
  end
end
else
  error('function has_class used on an element of type ' ..
        elem.t .. ' that cannot have classes.')
end
end

function Div(el)
  local env_class = get_env_class(el) -- nil if there is none
  if env_class then -- false if env_class is nil
    return { context('\\start'.. env_class), el, context('\\stop'.. env_class) }
  end
end
```

Notice that the intro, question or solution class need not be the first one, so that this would be recognized:

::: {.my-class .intro}

blabla

:::

Le Thursday 17 June 2021 à 08:12:06AM, denis.maier-NSENcxR/0n0@public.gmane.org a écrit :
> Yep, this is also what I was getting. 
> 
> But this minimal shows how to make it work:
> 
> ```lua -- works
> function Div(el)
>     return {pandoc.RawBlock('context', "\\start"), el, pandoc.RawBlock('context', "\\stop")}
> end
> ```
> 
> vs.
> 
> ```lua -- does not work!
> function Div(el)
>     return {pandoc.RawBlock('context', "\\start"), el.content, pandoc.RawBlock('context', "\\stop")}
> end
> ```
> 
> So, this here works:
> 
> ```lua
> function context(s)
>   return pandoc.RawBlock('context', s)
> end
> 
> function Div(el)
> 	if el.classes[1] == 'intro' then
> 		return { context('\\startintro'), el, context('\\stopintro') }
> 	end
> end
> ```
> 
> Maybe this should be a bit more generic though?
> 
> ```
> function context(s)
>   return pandoc.RawBlock('context', s)
> end
> 
> function Div(el)
> 	if el.classes[1] == 'intro' or 'question' or 'solution' then
> 		return { context('\\start'..el.classes[1]), el, context('\\stop'..el.classes[1]) }
> 	end
> end
> ```
> 
> As my lua skills are far below mediocre I bet there ways to make this nicer, e.g. by putting the relevant classes into a table and referring to that. And you may also want to pass arguments from your divs to the context \start...\stop construct. Think of this:
> 
> \startquestion[difficulty=easy]
> 
> How to build pandoc filters using lua?
> 
> \stopquestion?
> 
> Denis
> 
> > -----Ursprüngliche Nachricht-----
> > Von: 'juh' via pandoc-discuss <pandoc-discuss-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org>
> > Gesendet: Donnerstag, 17. Juni 2021 09:56
> > An: pandoc-discuss-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
> > Betreff: Re: Fenced Div to ConTeXt Environment (was: Markdown Fenced Div
> > to LaTeX Environment)
> > 
> > 
> > Am 17.06.21 um 08:54 schrieb BPJ:
> > > --filter/-F is for JSON filters. Lua filters need --lua-filter/-L
> > 
> > Thanks a lot! Now the error message is much more informative.
> > 
> > This is my filter:
> > 
> > function context(s)
> >    return pandoc.RawBlock('context', s)
> > end
> > 
> > function Div(el)
> >    if el.classes[1] == 'intro' then
> >      return { context('\\startparagraph{intro}'), el.content,
> > context('\\stopparagraph') }
> >    end
> > end
> > 
> > 
> > This is the error message
> > 
> > Error running filter filter.lua:
> > Could not read list: Could not get Block value: untagged value
> > 
> > Any hints?
> > juh
> > 
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