Re: Lua Filter: Detect Type of Inlines

[ThomasH <therch-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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Great, thanks.

On Friday, May 12, 2023 at 7:41:50 PM UTC+2 Albert Krewinkel wrote:

>
> ThomasH <the...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:
>
> > I want to detect the types of the inline elements of a paragraph. I
> > understand there is pandoc.utils.type() that basically does that, but
> > when I run
> >
> > function Para(para)
> >     for i = 1,#para.content,1 do
> >         print(tostring(pandoc.utils.type(para.content[i])))
> >     end
> > end
> >
> > all that is printed is "Inline" for all elements, not specific types
> > like Str, Span, Link or Image. How can I get at the specific types?
>
> The trick here is that we are using Haskell terminology: Inline is a
> *type*, and Str, Span, Link, etc. are *constructors* for this type. In
> Lua (and JSON) contexts, the property that identifies the name of the
> constructor of a value is called a "tag". Try this:
>
> ``` lua
> function Para(para)
> for i = 1,#para.content do
> print(para.content[i].tag))
> end
> end
> ```
>
> The `.t` property is an alias for `.tag` and can be used as well.
>
> I have plans to change the behavior of `pandoc.utils.type` and to make
> the function return two results. The first result would stay as-is, with
> the second result containing the constructor name. But I need to run
> more tests to ensure that this won't lead to performance degradation.
>
>
> -- 
> Albert Krewinkel
> GPG: 8eed e3e2 e8c5 6f18 81fe e836 388d c0b2 1f63 1124
>

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