I agree with you that centred or right alignment are presentational things (unless you’re trying to write Arabic or Hebrew, in which case left alignment is), but I strongly believe that being able to centre something on the page is nevertheless important to conveying meaning in certain narrow use cases, in the same way as a hard line break is within a postal address. I am attempting to use Pandoc to publish my mediocre attempts at fiction to various online repositories, and in examining the results of my past (pre-Pandoc) efforts, I have come to the conclusion that there is a marked difference in effect when some important bit of information is placed in the middle of the page, versus as just an unusually short paragraph clustered at the left edge with all the others.

I approve in principle of your proposed solution (“just use a ‹div› element and style it with CSS”); unfortunately, several of the submission formats I am forced to conform to are extremely crippled, and do not support either of those features of HTML. Rephrasing them as some other feature is far from simple from within the Lua custom writer.

Short of outputting to a native Haskell representation file, piping that to a filter program, and piping that result back through a second invocation of Pandoc, is there any way of invoking a transformational filter on the native AST as it is being processed? I keep seeing various language bindings (Perl, Python, PHP, etc.) that appear to be for doing just that, but I can’t find any mention of how you actually invoke a filter written to use one of them when you start the Pandoc tool.

On Saturday, 31 January 2015 22:45:48 UTC-8, John MacFarlane wrote:

+++ Gordon Steemson [Jan 31 15 18:25 ]:
>1) If someone, just to be difficult, needs to have literal ASCII arrows at
>the start and/or end of their actual output text block, can it be
>accommodated in a simple way by backslash-escaping? At what stage does that
>get stripped out — before the custom writer functions get called or after?

Before.  The escaping is resolved in the parser.  

 

>2) What would be involved in modifying the Pandoc markdown parser to
>recognize the obvious extension to this syntax, demonstrated below?

Well, it would be quite involved.  We'd need to modify the Pandoc
document model to add these alignment containers (though I suppose
we could use Div elements with special classes), then modify the
Markdown parser and all the writers.

Centering has come up before on this list (you can search for earlier
discussions).  My general feeling is that pandoc should focus on
structural elements of documents, and things like centering and
right-aligning are too presentational.

Note you can always put things in divs with classes, and format them
with CSS in HTML or with a simple filter in other formats.