18 lines
1.0 KiB
Markdown
18 lines
1.0 KiB
Markdown
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# Piecewise Readable Filter
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This is a pandoc lua filter that manipulates [fenced_divs](https://pandoc.org/MANUAL.html#extension-fenced_divs) in pandoc markdown.
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Inspired by [this joke](https://www.zhihu.com/question/586807834/answer/2973535981)(in chinese).
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Example: `example/What is a group.pdf`
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Useful refs:
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- https://pandoc.org/lua-filters.html
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- https://hackage-content.haskell.org/package/pandoc-types-1.23.1/docs/Text-Pandoc-Definition.html
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## How does this work?
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`filter.lua` walks the AST. There are some special leaf nodes with a `include` attr which is a string containing labels of some other divs to be included here.
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For each of `include` node `i`, we maintain a list `fa[i]` containing nodes with labels on the path `i -> root`. Then for each label `l` in `i`'s include list, one can see that every node in `fa[i]` depends on `l`. Thus we build a digraph G on labels. If G is a DAG, then we can use topological sort to rank its vertices and thus decide the order of substitution; Otherwise, G contains a directed cycle, the filter reports an error. |