Lua filters: favoured method to check an element's class?

Lua filters: favoured method to check an element's class?

[Julien Dutant]

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Hi all,

What's the favoured method to check an element's class in Lua filters? In 
the manual a couple of examples use the following:

if element.classes[1]="myclass" then

But that's not robust if the element has several classes and `myclass` is 
not the first:

::: {.otherclass .myclass}

I use a function that loops through the element.classes list (below). Have 
I missed a more straightforward method?

function has_class(elem, str)
for _,class in pairs(elem.classes) do
if class == str then 
return true 
end
end
return false
end

if has_class(elem, "myclass") then ...

All best,

Julien

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Re: Lua filters: favoured method to check an element's class?

[Albert Krewinkel]

Julien Dutant writes:

> What's the favoured method to check an element's class in Lua filters? In 
> the manual a couple of examples use the following:
>
> if element.classes[1]="myclass" then
>
> But that's not robust if the element has several classes and `myclass` is 
> not the first:

A convenient and robust check is `element.classes:includes 'myclass'`.

-- 
Albert Krewinkel
GPG: 8eed e3e2 e8c5 6f18 81fe  e836 388d c0b2 1f63 1124

Re: Lua filters: favoured method to check an element's class?

[Julien Dutant]

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Ah thanks I wasn't sure when the methods in pandoc.List could be used. 
Perfect!

J

On Sunday, December 13, 2020 at 10:17:18 PM UTC Albert Krewinkel wrote:

>
> Julien Dutant writes:
>
> > What's the favoured method to check an element's class in Lua filters? 
> In 
> > the manual a couple of examples use the following:
> >
> > if element.classes[1]="myclass" then
> >
> > But that's not robust if the element has several classes and `myclass` 
> is 
> > not the first:
>
> A convenient and robust check is `element.classes:includes 'myclass'`.
>
> -- 
> Albert Krewinkel
> GPG: 8eed e3e2 e8c5 6f18 81fe e836 388d c0b2 1f63 1124
>

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Re: Lua filters: favoured method to check an element's class?

[BPJ]

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If you want to know whether something is a table capable of doing some
known method you can generally do this:

``````lua
if 'table' == type(thing) then
  if 'function' == type(thing.includes) then
     io.stderr:write"A thing has a method 'includes'\n'"
  end
end
``````

In the context of Lua filters you would typically put the above code in a
dummy global Pandoc function and run the "filter" with just

``````commandline
pandoc -L dummy.lua
<Ctrl-D>
``````

and if the test is successful you will see the message.

On Windows you would press <Ctrl-Z> rather than <Ctrl-D>.

-- 
Better --help|less than helpless

Den mån 14 dec. 2020 00:21Julien Dutant <julien.dutant-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> skrev:

> Ah thanks I wasn't sure when the methods in pandoc.List could be used.
> Perfect!
>
> J
>
> On Sunday, December 13, 2020 at 10:17:18 PM UTC Albert Krewinkel wrote:
>
>>
>> Julien Dutant writes:
>>
>> > What's the favoured method to check an element's class in Lua filters?
>> In
>> > the manual a couple of examples use the following:
>> >
>> > if element.classes[1]="myclass" then
>> >
>> > But that's not robust if the element has several classes and `myclass`
>> is
>> > not the first:
>>
>> A convenient and robust check is `element.classes:includes 'myclass'`.
>>
>> --
>> Albert Krewinkel
>> GPG: 8eed e3e2 e8c5 6f18 81fe e836 388d c0b2 1f63 1124
>>
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> .
>

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Re: Lua filters: favoured method to check an element's class?

[Julien Dutant]

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Nice, thanks!

On Mon, 14 Dec 2020 at 10:00, BPJ <melroch-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> If you want to know whether something is a table capable of doing some
> known method you can generally do this:
>
> ``````lua
> if 'table' == type(thing) then
>   if 'function' == type(thing.includes) then
>      io.stderr:write"A thing has a method 'includes'\n'"
>   end
> end
> ``````
>
> In the context of Lua filters you would typically put the above code in a
> dummy global Pandoc function and run the "filter" with just
>
> ``````commandline
> pandoc -L dummy.lua
> <Ctrl-D>
> ``````
>
> and if the test is successful you will see the message.
>
> On Windows you would press <Ctrl-Z> rather than <Ctrl-D>.
>
> --
> Better --help|less than helpless
>
> Den mån 14 dec. 2020 00:21Julien Dutant <julien.dutant-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> skrev:
>
>> Ah thanks I wasn't sure when the methods in pandoc.List could be used.
>> Perfect!
>>
>> J
>>
>> On Sunday, December 13, 2020 at 10:17:18 PM UTC Albert Krewinkel wrote:
>>
>>>
>>> Julien Dutant writes:
>>>
>>> > What's the favoured method to check an element's class in Lua filters?
>>> In
>>> > the manual a couple of examples use the following:
>>> >
>>> > if element.classes[1]="myclass" then
>>> >
>>> > But that's not robust if the element has several classes and `myclass`
>>> is
>>> > not the first:
>>>
>>> A convenient and robust check is `element.classes:includes 'myclass'`.
>>>
>>> --
>>> Albert Krewinkel
>>> GPG: 8eed e3e2 e8c5 6f18 81fe e836 388d c0b2 1f63 1124
>>>
>> --
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>> .
>>
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> .
>


-- 

julien dutant

Department of Philosophy, King's College London
julien.dutant-3vygKqVCdQxaa/9Udqfwiw@public.gmane.org

http://julien.dutant.free.fr/

Strand

London WC2R 2LS

United Kingdom

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