--- author: - Albert Krewinkel - John MacFarlane date: 'December 6, 2017' title: Pandoc Lua Filters --- # Introduction Pandoc has long supported filters, which allow the pandoc abstract syntax tree (AST) to be manipulated between the parsing and the writing phase. [Traditional pandoc filters](https://pandoc.org/filters.html) accept a JSON representation of the pandoc AST and produce an altered JSON representation of the AST. They may be written in any programming language, and invoked from pandoc using the `--filter` option. Although traditional filters are very flexible, they have a couple of disadvantages. First, there is some overhead in writing JSON to stdout and reading it from stdin (twice, once on each side of the filter). Second, whether a filter will work will depend on details of the user's environment. A filter may require an interpreter for a certain programming language to be available, as well as a library for manipulating the pandoc AST in JSON form. One cannot simply provide a filter that can be used by anyone who has a certain version of the pandoc executable. Starting with pandoc 2.0, we have made it possible to write filters in lua without any external dependencies at all. A lua interpreter (version 5.3) and a lua library for creating pandoc filters is built into the pandoc executable. Pandoc data types are marshalled to lua directly, avoiding the overhead of writing JSON to stdout and reading it from stdin. Here is an example of a lua filter that converts strong emphasis to small caps: ``` lua return { { Strong = function (elem) return pandoc.SmallCaps(elem.c) end, } } ``` or equivalently, ``` lua function Strong(elem) return pandoc.SmallCaps(elem.c) end ``` This says: walk the AST, and when you find a Strong element, replace it with a SmallCaps element with the same content. To run it, save it in a file, say `smallcaps.lua`, and invoke pandoc with `--lua-filter=smallcaps.lua`. Here's a quick performance comparison, converting the pandoc manual (MANUAL.txt) to HTML, with versions of the same JSON filter written in compiled Haskell (`smallcaps`) and interpreted Python (`smallcaps.py`): Command Time --------------------------------------- ------- `pandoc` 1.01s `pandoc --filter ./smallcaps` 1.36s `pandoc --filter ./smallcaps.py` 1.40s `pandoc --lua-filter ./smallcaps.lua` 1.03s As you can see, the lua filter avoids the substantial overhead associated with marshalling to and from JSON over a pipe. # Lua filter structure Lua filters are tables with element names as keys and values consisting of functions acting on those elements. Filters are expected to be put into separate files and are passed via the `--lua-filter` command-line argument. For example, if a filter is defined in a file `current-date.lua`, then it would be applied like this: pandoc --lua-filter=current-date.lua -f markdown MANUAL.txt The `--lua-filter` option may be supplied multiple times. Pandoc applies all filters (including JSON filters specified via `--filter` and lua filters specified via `--lua-filter`) in the order they appear on the command line. Pandoc expects each lua file to return a list of filters. The filters in that list are called sequentially, each on the result of the previous filter. If there is no value returned by the filter script, then pandoc will try to generate a single filter by collecting all top-level functions whose names correspond to those of pandoc elements (e.g., `Str`, `Para`, `Meta`, or `Pandoc`). (That is why the two examples above are equivalent.) For each filter, the document is traversed and each element subjected to the filter. Elements for which the filter contains an entry (i.e. a function of the same name) are passed to lua element filtering function. In other words, filter entries will be called for each corresponding element in the document, getting the respective element as input. The return of a filter function must one of the following: - nil: this means that the object should remain unchanged. - a pandoc object: this must be of the same type as the input and will replace the original object. - a list of pandoc objects: these will replace the original object; the list is merged with the neighbors of the original objects (spliced into the list the original object belongs to); returning an empty list deletes the object. The function's output must result in an element of the same type as the input. This means a filter function acting on an inline element must return either nil, an inline, or a list of inlines, and a function filtering a block element must return one of nil, a block, or a list of block elements. Pandoc will throw an error if this condition is violated. If there is no function matching the element's node type, then the filtering system will look for a more general fallback function. Two fallback functions are supported, `Inline` and `Block`. Each matches elements of the respective type. Elements without matching functions are left untouched. See [module documentation](#module-pandoc) for a list of pandoc elements. ## Global variables Pandoc passes additional data to Lua filters by setting global variables. `FORMAT` : The global `FORMAT` is set to the format of the pandoc writer being used (`html5`, `latex`, etc.), so the behavior of a filter can be made conditional on the eventual output format. `PANDOC_READER_OPTIONS` : Table of the options which were provided to the parser. `PANDOC_VERSION` : Contains the pandoc version as a [Version object](#type-ref-Version) which behaves like a numerically indexed table, most significant number first. E.g., for pandoc 2.7.3, the value of the variable is equivalent to a table `{2, 7, 3}`. Use `tostring(PANDOC_VERSION)` to produce a version string. This variable is also set in custom writers. `PANDOC_API_VERSION` : Contains the version of the pandoc-types API against which pandoc was compiled. It is given as a numerically indexed table, most significant number first. E.g., if pandoc was compiled against pandoc-types 1.17.3, then the value of the variable will behave like the table `{1, 17, 3}`. Use `tostring(PANDOC_API_VERSION)` to produce a version string. This variable is also set in custom writers. `PANDOC_SCRIPT_FILE` : The name used to involve the filter. This value can be used to find files relative to the script file. This variable is also set in custom writers. `PANDOC_STATE` : The state shared by all readers and writers. It is used by pandoc to collect and pass information. The value of this variable is of type [CommonState](#type-ref-CommonState) and is read-only. # Pandoc Module The `pandoc` lua module is loaded into the filter's lua environment and provides a set of functions and constants to make creation and manipulation of elements easier. The global variable `pandoc` is bound to the module and should generally not be overwritten for this reason. Two major functionalities are provided by the module: element creator functions and access to some of pandoc's main functionalities. ## Element creation Element creator functions like `Str`, `Para`, and `Pandoc` are designed to allow easy creation of new elements that are simple to use and can be read back from the lua environment. Internally, pandoc uses these functions to create the lua objects which are passed to element filter functions. This means that elements created via this module will behave exactly as those elements accessible through the filter function parameter. ## Exposed pandoc functionality Some pandoc functions have been made available in lua: - [`walk_block`](#walk_block) and [`walk_inline`](#walk_inline) allow filters to be applied inside specific block or inline elements; - [`read`](#read) allows filters to parse strings into pandoc documents; - [`pipe`](#pipe) runs an external command with input from and output to strings; - the [`pandoc.mediabag`](#module-pandoc.mediabag) module allows access to the "mediabag," which stores binary content such as images that may be included in the final document; - the [`pandoc.utils`](#module-pandoc.utils) module contains various utility functions. # Lua interpreter initialization Initialization of pandoc's Lua interpreter can be controlled by placing a file `init.lua` in pandoc's data directory. A common use-case would be to load additional modules, or even to alter default modules. The following snippet is an example of code that might be useful when added to `init.lua`. The snippet adds all unicode-aware functions defined in the [`text` module](#module-text) to the default `string` module, prefixed with the string `uc_`. ``` lua for name, fn in pairs(require 'text') do string['uc_' .. name] = fn end ``` This makes it possible to apply these functions on strings using colon syntax (`mystring:uc_upper()`). # Examples The following filters are presented as examples. A repository of useful lua filters (which may also serve as good examples) is available at . ## Macro substitution The following filter converts the string `{{helloworld}}` into emphasized text "Hello, World". ``` lua return { { Str = function (elem) if elem.text == "{{helloworld}}" then return pandoc.Emph {pandoc.Str "Hello, World"} else return elem end end, } } ``` ## Center images in LaTeX and HTML output For LaTeX, wrap an image in LaTeX snippets which cause the image to be centered horizontally. In HTML, the image element's style attribute is used to achieve centering. ``` lua -- Filter images with this function if the target format is LaTeX. if FORMAT:match 'latex' then function Image (elem) -- Surround all images with image-centering raw LaTeX. return { pandoc.RawInline('latex', '\\hfill\\break{\\centering'), elem, pandoc.RawInline('latex', '\\par}') } end end -- Filter images with this function if the target format is HTML if FORMAT:match 'html' then function Image (elem) -- Use CSS style to center image elem.attributes.style = 'margin:auto; display: block;' return elem end end ``` ## Setting the date in the metadata This filter sets the date in the document's metadata to the current date: ``` lua function Meta(m) m.date = os.date("%B %e, %Y") return m end ``` ## Extracting information about links This filter prints a table of all the URLs linked to in the document, together with the number of links to that URL. ``` lua links = {} function Link (el) if links[el.target] then links[el.target] = links[el.target] + 1 else links[el.target] = 1 end return el end function Doc (blocks, meta) function strCell(str) return {pandoc.Plain{pandoc.Str(str)}} end local caption = {pandoc.Str "Link", pandoc.Space(), pandoc.Str "count"} local aligns = {pandoc.AlignDefault, pandoc.AlignLeft} local widths = {0.8, 0.2} local headers = {strCell "Target", strCell "Count"} local rows = {} for link, count in pairs(links) do rows[#rows + 1] = {strCell(link), strCell(count)} end return pandoc.Doc( {pandoc.Table(caption, aligns, widths, headers, rows)}, meta ) end ``` ## Replacing placeholders with their metadata value Lua filter functions are run in the order > *Inlines → Blocks → Meta → Pandoc*. Passing information from a higher level (e.g., metadata) to a lower level (e.g., inlines) is still possible by using two filters living in the same file: ``` lua local vars = {} function get_vars (meta) for k, v in pairs(meta) do if type(v) == 'table' and v.t == 'MetaInlines' then vars["%" .. k .. "%"] = {table.unpack(v)} end end end function replace (el) if vars[el.text] then return pandoc.Span(vars[el.text]) else return el end end return {{Meta = get_vars}, {Str = replace}} ``` If the contents of file `occupations.md` is ``` markdown --- name: Samuel Q. Smith occupation: Professor of Phrenology --- Name : %name% Occupation : %occupation% ``` then running `pandoc --lua-filter=meta-vars.lua occupations.md` will output: ``` html
Name

Samuel Q. Smith

Occupation

Professor of Phrenology

``` ## Modifying pandoc's `MANUAL.txt` for man pages This is the filter we use when converting `MANUAL.txt` to man pages. It converts level-1 headers to uppercase (using `walk_block` to transform inline elements inside headers), removes footnotes, and replaces links with regular text. ``` lua -- we use preloaded text to get a UTF-8 aware 'upper' function local text = require('text') function Header(el) if el.level == 1 then return pandoc.walk_block(el, { Str = function(el) return pandoc.Str(text.upper(el.text)) end }) end end function Link(el) return el.content end function Note(el) return {} end ``` ## Creating a handout from a paper This filter extracts all the numbered examples, section headers, block quotes, and figures from a document, in addition to any divs with class `handout`. (Note that only blocks at the "outer level" are included; this ignores blocks inside nested constructs, like list items.) ``` lua -- creates a handout from an article, using its headings, -- blockquotes, numbered examples, figures, and any -- Divs with class "handout" function Pandoc(doc) local hblocks = {} for i,el in pairs(doc.blocks) do if (el.t == "Div" and el.classes[1] == "handout") or (el.t == "BlockQuote") or (el.t == "OrderedList" and el.style == "Example") or (el.t == "Para" and #el.c == 1 and el.c[1].t == "Image") or (el.t == "Header") then table.insert(hblocks, el) end end return pandoc.Pandoc(hblocks, doc.meta) end ``` ## Counting words in a document This filter counts the words in the body of a document (omitting metadata like titles and abstracts), including words in code. It should be more accurate than `wc -w` run directly on a Markdown document, since the latter will count markup characters, like the `#` in front of an ATX header, or tags in HTML documents, as words. To run it, `pandoc --lua-filter wordcount.lua myfile.md`. ``` lua -- counts words in a document words = 0 wordcount = { Str = function(el) -- we don't count a word if it's entirely punctuation: if el.text:match("%P") then words = words + 1 end end, Code = function(el) _,n = el.text:gsub("%S+","") words = words + n end, CodeBlock = function(el) _,n = el.text:gsub("%S+","") words = words + n end } function Pandoc(el) -- skip metadata, just count body: pandoc.walk_block(pandoc.Div(el.blocks), wordcount) print(words .. " words in body") os.exit(0) end ``` ## Converting ABC code to music notation This filter replaces code blocks with class `abc` with images created by running their contents through `abcm2ps` and ImageMagick's `convert`. (For more on ABC notation, see .) Images are added to the mediabag. For output to binary formats, pandoc will use images in the mediabag. For textual formats, use `--extract-media` to specify a directory where the files in the mediabag will be written, or (for HTML only) use `--self-contained`. ``` lua -- Pandoc filter to process code blocks with class "abc" containing -- ABC notation into images. -- -- * Assumes that abcm2ps and ImageMagick's convert are in the path. -- * For textual output formats, use --extract-media=abc-images -- * For HTML formats, you may alternatively use --self-contained local filetypes = { html = {"png", "image/png"} , latex = {"pdf", "application/pdf"} } local filetype = filetypes[FORMAT][1] or "png" local mimetype = filetypes[FORMAT][2] or "image/png" local function abc2eps(abc, filetype) local eps = pandoc.pipe("abcm2ps", {"-q", "-O", "-", "-"}, abc) local final = pandoc.pipe("convert", {"-", filetype .. ":-"}, eps) return final end function CodeBlock(block) if block.classes[1] == "abc" then local img = abc2eps(block.text, filetype) local fname = pandoc.sha1(img) .. "." .. filetype pandoc.mediabag.insert(fname, mimetype, img) return pandoc.Para{ pandoc.Image({pandoc.Str("abc tune")}, fname) } end end ``` ## Building images with tikz This filter converts raw LaTeX tikz environments into images. It works with both PDF and HTML output. The tikz code is compiled to an image using `pdflatex`, and the image is converted from pdf to svg format using [`pdf2svg`](https://github.com/dawbarton/pdf2svg), so both of these must be in the system path. Converted images are cached in the working directory and given filenames based on a hash of the source, so that they need not be regenerated each time the document is built. (A more sophisticated version of this might put these in a special cache directory.) ``` lua local function tikz2image(src, filetype, outfile) local tmp = os.tmpname() local tmpdir = string.match(tmp, "^(.*[\\/])") or "." local f = io.open(tmp .. ".tex", 'w') f:write("\\documentclass{standalone}\n\\usepackage{xcolor}\n\\usepackage{tikz}\n\\begin{document}\n\\nopagecolor\n") f:write(src) f:write("\n\\end{document}\n") f:close() os.execute("pdflatex -output-directory " .. tmpdir .. " " .. tmp) if filetype == 'pdf' then os.rename(tmp .. ".pdf", outfile) else os.execute("pdf2svg " .. tmp .. ".pdf " .. outfile) end os.remove(tmp .. ".tex") os.remove(tmp .. ".pdf") os.remove(tmp .. ".log") os.remove(tmp .. ".aux") end extension_for = { html = 'svg', html4 = 'svg', html5 = 'svg', latex = 'pdf', beamer = 'pdf' } local function file_exists(name) local f = io.open(name, 'r') if f ~= nil then io.close(f) return true else return false end end local function starts_with(start, str) return str:sub(1, #start) == start end function RawBlock(el) if starts_with("\\begin{tikzpicture}", el.text) then local filetype = extension_for[FORMAT] or "svg" local fname = pandoc.sha1(el.text) .. "." .. filetype if not file_exists(fname) then tikz2image(el.text, filetype, fname) end return pandoc.Para({pandoc.Image({}, fname)}) else return el end end ``` Example of use: pandoc --lua-filter tikz.lua -s -o cycle.html <, >=latex] ({360/\n * (\s - 1)+\margin}:\radius) arc ({360/\n * (\s - 1)+\margin}:{360/\n * (\s)-\margin}:\radius); } \end{tikzpicture} EOF # Lua type reference This section describes the types of objects available to Lua filters. See the [pandoc module](#module-pandoc%7D) for functions to create these objects. ## Shared Properties ### `clone` `clone ()` All instances of the types listed here, with the exception of read-only objects, can be cloned via the `clone()` method. Usage: local emph = pandoc.Emph {pandoc.Str 'important'} local cloned_emph = emph:clone() -- note the colon ## Pandoc {#type-ref-pandoc} Pandoc document Object equality is determined via [`pandoc.utils.equals`](#utils-equals). `blocks` : document content ([List](#module-pandoc.list) of [Block](#type-ref-Block)s) `meta` : document meta information ([Meta](#Meta) object) ## Meta {#type-ref-meta} Meta information on a document; string-indexed collection of [MetaValue](#type-ref-MetaValue)s. Object equality is determined via [`pandoc.utils.equals`](#utils-equals). ## MetaValue {#type-ref-MetaValue} Document meta information items. Object equality is determined via [`pandoc.utils.equals`](#utils-equals). ### MetaBlocks {#type-ref-MetaBlocks} A list of blocks usable as meta value ([List](#module-pandoc.list) of [Block](#type-ref-Block)s) Fields: `tag`, `t` : the literal `MetaBlocks` (string) ### MetaBool {#type-ref-MetaBool} Plain Lua boolean value (boolean) ### MetaInlines {#type-ref-MetaInlines} List of inlines used in metadata ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) Fields: `tag`, `t` : the literal `MetaInlines` (string) ### MetaList {#type-ref-iMetaList} A list of other [MetaValue](#type-ref-MetaValue)s. ([List](#module-pandoc.list)) Fields: `tag`, `t` : the literal `MetaList` (string) ### MetaMap {#type-ref-MetaMap} A string-indexed map of meta-values. (table) Fields: `tag`, `t` : the literal `MetaMap` (string) *Note*: The fields will be shadowed if the map contains a field with the same name as those listed. ### MetaString {#type-ref-MetaString} Plain Lua string value (string) ## Block {#type-ref-Block} Object equality is determined via [`pandoc.utils.equals`](#utils-equals). ### BlockQuote {#type-ref-BlockQuote} A block quote element content: : block content ([List](#module-pandoc.list) of [Block](#type-ref-Block)s) `tag`, `t` : the literal `BlockQuote` (string) ### BulletList {#type-ref-BulletList} A bullet list `content` : list of items ([List](#module-pandoc.list) of [Block](#type-ref-Block)s) `tag`, `t` : the literal `BulletList` (string) ### CodeBlock {#type-ref-CodeBlock} Block of code. `text` : code string (string) `attr` : element attributes ([Attr](#type-ref-Attr)) `identifier` : alias for `attr.identifier` (string) `classes` : alias for `attr.classes` ([List](#module-pandoc.list) of strings) `attributes` : alias for `attr.attributes` ([Attributes](#type-ref-Attributes)) `tag`, `t` : the literal `CodeBlock` (string) ### DefinitionList {#type-ref-DefinitionList} Definition list, containing terms and their explanation. `content` : list of items `tag`, `t` : the literal `DefinitionList` (string) ### Div {#type-ref-Div} Generic block container with attributes `content` : block content ([List](#module-pandoc.list) of [Block](#type-ref-Block)s) `attr` : element attributes ([Attr](#type-ref-Attr)) `identifier` : alias for `attr.identifier` (string) `classes` : alias for `attr.classes` ([List](#module-pandoc.list) of strings) `attributes` : alias for `attr.attributes` ([Attributes](#type-ref-Attributes)) `tag`, `t` : the literal `Div` (string) ### Header {#type-ref-Header} Creates a header element. `level` : header level (integer) `content` : inline content ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `attr` : element attributes ([Attr](#type-ref-Attr)) `identifier` : alias for `attr.identifier` (string) `classes` : alias for `attr.classes` ([List](#module-pandoc.list) of strings) `attributes` : alias for `attr.attributes` ([Attributes](#type-ref-Attributes)) `tag`, `t` : the literal `Header` (string) ### HorizontalRule {#type-ref-HorizontalRule} A horizontal rule. `tag`, `t` : the literal `HorizontalRule` (string) ### LineBlock {#type-ref-LineBlock} A line block, i.e. a list of lines, each separated from the next by a newline. `content` : inline content `tag`, `t` : the literal `LineBlock` (string) ### Null {#type-ref-Null} A null element; this element never produces any output in the target format. `tag`, `t` : the literal `Null` (string) ### OrderedList {#type-ref-OrderedList} An ordered list. `content` : list items ([List](#module-pandoc.list) of [Block](#type-ref-Block)s) `listAttributes` : list parameters ([ListAttributes](#ListAttributes)) `start` : alias for `listAttributes.start` (integer) `style` : alias for `listAttributes.style` (string) `delimiter` : alias for `listAttributes.delimiter` (string) `tag`, `t` : the literal `OrderedList` (string) ### Para {#type-ref-Para} A paragraph `content` : inline content ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `tag`, `t` : the literal `Para` (string) ### Plain {#type-ref-Plain} Plain text, not a paragraph `content` : inline content ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `tag`, `t` : the literal `Plain` (string) ### RawBlock {#type-ref-RawBlock} Raw content of a specified format. `format` : format of content (string) `text` : raw content (string) `tag`, `t` : the literal `RawBlock` (string) ### Table {#type-ref-Table} A table. `caption` : table caption ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `aligns` : column alignments ([List](#module-pandoc.list) of [Alignment](#type-ref-Alignment)s) `widths` : column widths (number) `headers` : header row ([List](#module-pandoc.list) of [table cells](#type-ref-table-cell)) `rows` : table rows ([List](#module-pandoc.list) of [List](#module-pandoc.list)s of [table cells](#type-ref-table-cell)) `tag`, `t` : the literal `Table` (string) A [table cell]{#table-cell} is a list of blocks. *[Alignment]{#Alignment}* is a string value indicating the horizontal alignment of a table column. `AlignLeft`, `AlignRight`, and `AlignCenter` leads cell content tob be left-aligned, right-aligned, and centered, respectively. The default alignment is `AlignDefault` (often equivalent to centered). ## Inline {#type-ref-Inline} Object equality is determined via [`pandoc.utils.equals`](#utils-equals). ### Cite {#type-ref-Cite} Citation `content` : ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `citations` : citation entries ([List](#module-pandoc.list) of [citations](#type-ref-Citation)) `tag`, `t` : the literal `Cite` (string) ### Code {#type-ref-Code} Inline code `text` : code string (string) `attr` : attributes ([Attr](#type-ref-Attr)) `identifier` : alias for `attr.identifier` (string) `classes` : alias for `attr.classes` ([List](#module-pandoc.list) of strings) `attributes` : alias for `attr.attributes` ([Attributes](#type-ref-Attributes)) `tag`, `t` : the literal `Code` (string) ### Emph {#type-ref-Emph} Emphasized text `content` : inline content ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `tag`, `t` : the literal `Emph` (string) ### Image {#type-ref-Image} Image: alt text (list of inlines), target `attr` : attributes ([Attr](#type-ref-Attr)) `caption` : text used to describe the image ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `src` : path to the image file (string) `title` : brief image description `identifier` : alias for `attr.identifier` (string) `classes` : alias for `attr.classes` ([List](#module-pandoc.list) of strings) `attributes` : alias for `attr.attributes` ([Attributes](#type-ref-Attributes)) `tag`, `t` : the literal `Image` (string) ### LineBreak {#type-ref-LineBreak} Hard line break `tag`, `t` : the literal `LineBreak` (string) ### Link {#type-ref-Link} Hyperlink: alt text (list of inlines), target `attr` : attributes ([Attr](#type-ref-Attr)) `content` : text for this link ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `target` : the link target (string) `identifier` : alias for `attr.identifier` (string) `classes` : alias for `attr.classes` ([List](#module-pandoc.list) of strings) `attributes` : alias for `attr.attributes` ([Attributes](#type-ref-Attributes)) `tag`, `t` : the literal `Link` (string) ### Math {#type-ref-Math} TeX math (literal) `mathtype` : specifier determining whether the math content should be shown inline (`InlineMath`) or on a separate line (`DisplayMath`) (string) `text` : math content (string) `tag`, `t` : the literal `Math` (string) ### Note {#type-ref-Note} Footnote or endnote `content` : ([List](#module-pandoc.list) of [Block](#type-ref-Block)s) `tag`, `t` : the literal `Note` (string) ### Quoted {#type-ref-Quoted} Quoted text `quotetype` : type of quotes to be used; one of `SingleQuote` or `DoubleQuote` (string) `content` : quoted text ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `tag`, `t` : the literal `Quoted` (string) ### RawInline {#type-ref-RawInline} Raw inline `format` : the format of the content (string) `text` : raw content (string) `tag`, `t` : the literal `RawInline` (string) ### SmallCaps {#type-ref-SmallCaps} Small caps text `content` : ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `tag`, `t` : the literal `SmallCaps` (string) ### SoftBreak {#type-ref-SoftBreak} Soft line break `tag`, `t` : the literal `SoftBreak` (string) ### Space {#type-ref-Space} Inter-word space `tag`, `t` : the literal `Space` (string) ### Span {#type-ref-Span} Generic inline container with attributes `attr` : attributes ([Attr](#type-ref-Attr)) `content` : wrapped content ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `identifier` : alias for `attr.identifier` (string) `classes` : alias for `attr.classes` ([List](#module-pandoc.list) of strings) `attributes` : alias for `attr.attributes` ([Attributes](#type-ref-Attributes)) `tag`, `t` : the literal `Span` (string) ### Str {#type-ref-Str} Text `text` : content (string) `tag`, `t` : the literal `Str` (string) ### Strikeout {#type-ref-Strikeout} Strikeout text `content` : inline content ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `tag`, `t` : the literal `Strikeout` (string) ### Strong {#type-ref-Strong} Strongly emphasized text `content` : inline content ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `tag`, `t` : the literal `Strong` (string) ### Subscript {#type-ref-Subscript} Subscripted text `content` : inline content ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `tag`, `t` : the literal `Subscript` (string) ### Superscript {#type-ref-Superscript} Superscripted text `content` : inline content ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `tag`, `t` : the literal `Superscript` (string) ## Element components ### Attr {#type-ref-Attr} A set of element attributes. Values of this type can be created with the [`pandoc.Attr`](#Attr) constructor. For convenience, it is usually not necessary to construct the value directly if it is part of an element, and it is sufficient to pass an HTML-like table. E.g., to create a span with identifier "text" and classes "a" and "b", on can write: local span = pandoc.Span('text', {id = 'text', class = 'a b'}) This also works when using the `attr` setter: local span = pandoc.Span 'text' span.attr = {id = 'text', class = 'a b', other_attribute = '1'} Object equality is determined via [`pandoc.utils.equals`](#utils-equals). `identifier` : element identifier (string) `classes` : element classes ([List](#module-pandoc.list) of strings) `attributes` : collection of key/value pairs ([Attributes](#type-ref-Attributes)) ### Attributes {#type-ref-Attributes} List of key/value pairs. Values can be accessed by using keys as indices to the list table. ### Citation {#type-ref-Citation} Single citation entry Object equality is determined via [`pandoc.utils.equals`](#utils-equals). `id` : citation identifier, e.g., a bibtex key (string) `mode` : citation mode, one of `AuthorInText`, `SuppressAuthor`, or `NormalCitation` (string) `prefix` : citation prefix ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `suffix` : citation suffix ([List](#module-pandoc.list) of [Inline](#type-ref-Inline)s) `note_num` : note number (integer) `hash` : hash (integer) ### ListAttributes {#type-ref-ListAttributes} List attributes Object equality is determined via [`pandoc.utils.equals`](#utils-equals). `start` : number of the first list item (integer) `style` : style used for list numbers; possible values are `DefaultStyle`, `Example`, `Decimal`, `LowerRoman`, `UpperRoman`, `LowerAlpha`, and `UpperAlpha` (string) `delimiter` : delimiter of list numbers; one of `DefaultDelim`, `Period`, `OneParen`, and `TwoParens` (string) ## ReaderOptions {#type-ref-ReaderOptions} Pandoc reader options `abbreviations` : set of known abbreviations (set of strings) `columns` : number of columns in terminal (integer) `default_image_extension` : default extension for images (string) `extensions` : string representation of the syntax extensions bit field (string) `indented_code_classes` : default classes for indented code blocks (list of strings) `standalone` : whether the input was a standalone document with header (boolean) `strip_comments` : HTML comments are stripped instead of parsed as raw HTML (boolean) `tab_stop` : width (i.e. equivalent number of spaces) of tab stops (integer) `track_changes` : track changes setting for docx; one of `AcceptChanges`, `RejectChanges`, and `AllChanges` (string) ## CommonState {#type-ref-CommonState} The state used by pandoc to collect information and make it available to readers and writers. `input_files` : List of input files from command line ([List](#module-pandoc.list) of strings) `output_file` : Output file from command line (string or nil) `log` : A list of log messages in reverse order ([List](#module-pandoc.list) of [LogMessage](#type-ref-LogMessage)s) `request_headers` : Headers to add for HTTP requests; table with header names as keys and header contents as value (table) `resource_path` : Path to search for resources like included images ([List](#module-pandoc.list) of strings) `source_url` : Absolute URL or directory of first source file (string or nil) `user_data_dir` : Directory to search for data files (string or nil) `trace` : Whether tracing messages are issued (boolean) `verbosity` : Verbosity level; one of `INFO`, `WARNING`, `ERROR` (string) ## LogMessage {#type-ref-LogMessage} A pandoc log message. Object have no fields, but can be converted to a string via `tostring`. ## Version {#type-ref-Version} A version object. This represents a software version like "2.7.3". The object behaves like a numerically indexed table, i.e., if `version` represents the version `2.7.3`, then version[1] == 2 version[2] == 7 version[3] == 3 #version == 3 -- length Comparisons are performed element-wise, i.e. Version '1.12' > Version '1.9' ### `must_be_at_least` `must_be_at_least(actual, expected [, error_message])` Raise an error message if the actual version is older than the expected version; does nothing if actual is equal to or newer than the expected version. Parameters: `actual` : actual version specifier ([Version](#type-ref-Version)) `expected` : minimum expected version ([Version](#type-ref-Version)) `error_message` : optional error message template. The string is used as format string, with the expected and actual versions as arguments. Defaults to `"expected version %s or newer, got %s"`. Usage: PANDOC_VERSION:must_be_at_least '2.7.3' PANDOC_API_VERSION:must_be_at_least( '1.17.4', 'pandoc-types is too old: expected version %s, got %s' ) # Module text UTF-8 aware text manipulation functions, implemented in Haskell. The module is made available as part of the `pandoc` module via `pandoc.text`. The text module can also be loaded explicitly: ``` lua -- uppercase all regular text in a document: text = require 'text' function Str (s) s.text = text.upper(s.text) return s end ``` ### lower {#text-lower} `lower (s)` Returns a copy of a UTF-8 string, converted to lowercase. ### upper {#text-upper} `upper (s)` Returns a copy of a UTF-8 string, converted to uppercase. ### reverse {#text-reverse} `reverse (s)` Returns a copy of a UTF-8 string, with characters reversed. ### len {#text-len} `len (s)` Returns the length of a UTF-8 string. ### sub {#text-sub} `sub (s)` Returns a substring of a UTF-8 string, using Lua's string indexing rules. # Module pandoc Lua functions for pandoc scripts. ## Pandoc Document [`Pandoc (blocks[, meta])`]{#Pandoc} : A complete pandoc document Parameters: `blocks`: : document content `meta`: : document meta data ## Meta {#meta} [`Meta (table)`]{#Meta} : Create a new Meta object. Parameters: `table`: : table containing document meta information ## MetaValue {#metavalue} [`MetaBlocks (blocks)`]{#MetaBlocks} : Meta blocks Parameters: `blocks`: : blocks [`MetaInlines (inlines)`]{#MetaInlines} : Meta inlines Parameters: `inlines`: : inlines [`MetaList (meta_values)`]{#MetaList} : Meta list Parameters: `meta_values`: : list of meta values [`MetaMap (key_value_map)`]{#MetaMap} : Meta map Parameters: `key_value_map`: : a string-indexed map of meta values [`MetaString (str)`]{#MetaString} : Creates string to be used in meta data. Parameters: `str`: : string value [`MetaBool (bool)`]{#MetaBool} : Creates boolean to be used in meta data. Parameters: `bool`: : boolean value ## Blocks [`Block`]{#Block} : Block elements [`BlockQuote (content)`]{#BlockQuote} : Creates a block quote element Parameters: `content`: : block content Returns: block quote element [`BulletList (content)`]{#BulletList} : Creates a bullet (i.e. Parameters: `content`: : list of items Returns: bullet list element [`CodeBlock (text[, attr])`]{#CodeBlock} : Creates a code block element Parameters: `text`: : code string `attr`: : element attributes Returns: code block element [`DefinitionList (content)`]{#DefinitionList} : Creates a definition list, containing terms and their explanation. Parameters: `content`: : list of items Returns: definition list element [`Div (content[, attr])`]{#Div} : Creates a div element Parameters: `content`: : block content `attr`: : element attributes Returns: div element [`Header (level, content[, attr])`]{#Header} : Creates a header element. Parameters: `level`: : header level `content`: : inline content `attr`: : element attributes Returns: header element [`HorizontalRule ()`]{#HorizontalRule} : Creates a horizontal rule. Returns: horizontal rule [`LineBlock (content)`]{#LineBlock} : Creates a line block element. Parameters: `content`: : inline content Returns: line block element [`Null ()`]{#Null} : Creates a null element. Returns: null element [`OrderedList (items[, listAttributes])`]{#OrderedList} : Creates an ordered list. Parameters: `items`: : list items `listAttributes`: : list parameters Returns: ordered list element [`Para (content)`]{#Para} : Creates a para element. Parameters: `content`: : inline content Returns: paragraph element [`Plain (content)`]{#Plain} : Creates a plain element. Parameters: `content`: : inline content Returns: plain element [`RawBlock (format, text)`]{#RawBlock} : Creates a raw content block of the specified format. Parameters: `format`: : format of content `text`: : string content Returns: raw block element [`Table (caption, aligns, widths, headers, rows)`]{#Table} : Creates a table element. Parameters: `caption`: : table caption `aligns`: : alignments `widths`: : column widths `headers`: : header row `rows`: : table rows Returns: table element ## Inline {#inline} [`Inline`]{#Inline} : Inline element class [`Cite (content, citations)`]{#Cite} : Creates a Cite inline element Parameters: `content`: : List of inlines `citations`: : List of citations Returns: citations element [`Code (text[, attr])`]{#Code} : Creates a Code inline element Parameters: `text`: : code string `attr`: : additional attributes Returns: code element [`Emph (content)`]{#Emph} : Creates an inline element representing emphasised text. Parameters: `content`: : inline content Returns: emphasis element [`Image (caption, src[, title[, attr]])`]{#Image} : Creates a Image inline element Parameters: `caption`: : text used to describe the image `src`: : path to the image file `title`: : brief image description `attr`: : additional attributes Returns: image element [`LineBreak ()`]{#LineBreak} : Create a LineBreak inline element Returns: linebreak element [`Link (content, target[, title[, attr]])`]{#Link} : Creates a link inline element, usually a hyperlink. Parameters: `content`: : text for this link `target`: : the link target `title`: : brief link description `attr`: : additional attributes Returns: image element [`Math (mathtype, text)`]{#Math} : Creates a Math element, either inline or displayed. Parameters: `mathtype`: : rendering specifier `text`: : Math content Returns: Math element [`DisplayMath (text)`]{#DisplayMath} : Creates a DisplayMath element (DEPRECATED). Parameters: `text`: : Math content Returns: Math element [`InlineMath (text)`]{#InlineMath} : Creates an InlineMath inline element (DEPRECATED). Parameters: `text`: : Math content Returns: Math element [`Note (content)`]{#Note} : Creates a Note inline element Parameters: `content`: : footnote block content [`Quoted (quotetype, content)`]{#Quoted} : Creates a Quoted inline element given the quote type and quoted content. Parameters: `quotetype`: : type of quotes to be used `content`: : inline content Returns: quoted element [`SingleQuoted (content)`]{#SingleQuoted} : Creates a single-quoted inline element (DEPRECATED). Parameters: `content`: : inline content Returns: quoted element See also: [Quoted](#Quoted) [`DoubleQuoted (content)`]{#DoubleQuoted} : Creates a single-quoted inline element (DEPRECATED). Parameters: `content`: : inline content Returns: quoted element See also: [Quoted](#Quoted) [`RawInline (format, text)`]{#RawInline} : Creates a RawInline inline element Parameters: `format`: : format of the contents `text`: : string content Returns: raw inline element [`SmallCaps (content)`]{#SmallCaps} : Creates text rendered in small caps Parameters: `content`: : inline content Returns: smallcaps element [`SoftBreak ()`]{#SoftBreak} : Creates a SoftBreak inline element. Returns: softbreak element [`Space ()`]{#Space} : Create a Space inline element Returns: space element [`Span (content[, attr])`]{#Span} : Creates a Span inline element Parameters: `content`: : inline content `attr`: : additional attributes Returns: span element [`Str (text)`]{#Str} : Creates a Str inline element Parameters: `text`: : content Returns: string element [`Strikeout (content)`]{#Strikeout} : Creates text which is striked out. Parameters: `content`: : inline content Returns: strikeout element [`Strong (content)`]{#Strong} : Creates a Strong element, whose text is usually displayed in a bold font. Parameters: `content`: : inline content Returns: strong element [`Subscript (content)`]{#Subscript} : Creates a Subscript inline element Parameters: `content`: : inline content Returns: subscript element [`Superscript (content)`]{#Superscript} : Creates a Superscript inline element Parameters: `content`: : inline content Returns: strong element ## Element components {#element-components-create} [`Attr ([identifier[, classes[, attributes]]])`]{#Attr} : Create a new set of attributes (Attr). Parameters: `identifier`: : element identifier `classes`: : element classes `attributes`: : table containing string keys and values Returns: element attributes [`Citation (id, mode[, prefix[, suffix[, note_num[, hash]]]])`]{#Citation} : Creates a single citation. Parameters: `id`: : citation identifier (like a bibtex key) `mode`: : citation mode `prefix`: : citation prefix `suffix`: : citation suffix `note_num`: : note number `hash`: : hash number [`ListAttributes ([start[, style[, delimiter]]])`]{#ListAttributes} : Creates a set of list attributes. Parameters: `start`: : number of the first list item `style`: : style used for list numbering `delimiter`: : delimiter of list numbers Returns: list attributes table ## Constants [`AuthorInText`]{#AuthorInText} : Author name is mentioned in the text. See also: [Citation](#Citation) [`SuppressAuthor`]{#SuppressAuthor} : Author name is suppressed. See also: [Citation](#Citation) [`NormalCitation`]{#NormalCitation} : Default citation style is used. See also: [Citation](#Citation) [`AlignLeft`]{#AlignLeft} : Table cells aligned left. See also: [Table](#Table) [`AlignRight`]{#AlignRight} : Table cells right-aligned. See also: [Table](#Table) [`AlignCenter`]{#AlignCenter} : Table cell content is centered. See also: [Table](#Table) [`AlignDefault`]{#AlignDefault} : Table cells are alignment is unaltered. See also: [Table](#Table) [`DefaultDelim`]{#DefaultDelim} : Default list number delimiters are used. See also: [OrderedList](#OrderedList) [`Period`]{#Period} : List numbers are delimited by a period. See also: [OrderedList](#OrderedList) [`OneParen`]{#OneParen} : List numbers are delimited by a single parenthesis. See also: [OrderedList](#OrderedList) [`TwoParens`]{#TwoParens} : List numbers are delimited by a double parentheses. See also: [OrderedList](#OrderedList) [`DefaultStyle`]{#DefaultStyle} : List are numbered in the default style See also: [OrderedList](#OrderedList) [`Example`]{#Example} : List items are numbered as examples. See also: [OrderedList](#OrderedList) [`Decimal`]{#Decimal} : List are numbered using decimal integers. See also: [OrderedList](#OrderedList) [`LowerRoman`]{#LowerRoman} : List are numbered using lower-case roman numerals. See also: [OrderedList](#OrderedList) [`UpperRoman`]{#UpperRoman} : List are numbered using upper-case roman numerals See also: [OrderedList](#OrderedList) [`LowerAlpha`]{#LowerAlpha} : List are numbered using lower-case alphabetic characters. See also: [OrderedList](#OrderedList) [`UpperAlpha`]{#UpperAlpha} : List are numbered using upper-case alphabetic characters. See also: [OrderedList](#OrderedList) [`sha1`]{#sha1} : Functions which have moved to different modules ## Helper functions ### pipe `pipe (command, args, input)` Runs command with arguments, passing it some input, and returns the output. Returns: - Output of command. Raises: - A table containing the keys `command`, `error_code`, and `output` is thrown if the command exits with a non-zero error code. Usage: local output = pandoc.pipe("sed", {"-e","s/a/b/"}, "abc") ### walk\_block `walk_block (element, filter)` Apply a filter inside a block element, walking its contents. Parameters: `element`: : the block element `filter`: : a lua filter (table of functions) to be applied within the block element Returns: the transformed block element ### walk\_inline `walk_inline (element, filter)` Apply a filter inside an inline element, walking its contents. Parameters: `element`: : the inline element `filter`: : a lua filter (table of functions) to be applied within the inline element Returns: the transformed inline element ### read `read (markup[, format])` Parse the given string into a Pandoc document. Parameters: `markup`: : the markup to be parsed `format`: : format specification, defaults to `"markdown"`. Returns: pandoc document Usage: local org_markup = "/emphasis/" -- Input to be read local document = pandoc.read(org_markup, "org") -- Get the first block of the document local block = document.blocks[1] -- The inline element in that block is an `Emph` assert(block.content[1].t == "Emph") # Module pandoc.utils This module exposes internal pandoc functions and utility functions. The module is loaded as part of the `pandoc` module and available as `pandoc.utils`. In versions up-to and including pandoc 2.6, this module had to be loaded explicitly. Example: local utils = require 'pandoc.utils' Use this for backwards compatibility. ### blocks\_to\_inlines {#utils-blocks_to_inlines} `blocks_to_inlines (blocks[, sep])` Squash a list of blocks into a list of inlines. Parameters: `blocks`: : List of [Blocks](#Blocks) to be flattened. `sep`: : List of [Inlines](#Inlines) inserted as separator between two consecutive blocks; defaults to `{ pandoc.Space(), pandoc.Str'¶', pandoc.Space()}`. Returns: - List of [Inlines](#Inlines) Usage: local blocks = { pandoc.Para{ pandoc.Str 'Paragraph1' }, pandoc.Para{ pandoc.Emph 'Paragraph2' } } local inlines = pandoc.utils.blocks_to_inlines(blocks) -- inlines = { -- pandoc.Str 'Paragraph1', -- pandoc.Space(), pandoc.Str'¶', pandoc.Space(), -- pandoc.Emph{ pandoc.Str 'Paragraph2' } -- } ### equals {#utils-equals} `equals (element1, element2)` Test equality of AST elements. Elements in Lua are considered equal if and only if the objects obtained by unmarshaling are equal. Parameters: `element1`, `element2`: : Objects to be compared. Acceptable input types are [Pandoc](#type-ref-pandoc), [Meta](#type-ref-meta), [MetaValue](#type-ref-MetaValue), [Block](#type-ref-Block), [Inline](#type-ref-Inline), [Attr](#type-ref-Attr), [ListAttributes](#type-ref-ListAttributes), and [Citation](#type-ref-Citation). Returns: - Whether the two objects represent the same element (boolean) ### make\_sections {#utils-make_sections} `make_sections (number_sections, base_level, blocks)` Converst list of [Blocks](#Blocks) into sections. `Div`s will be created beginning at each `Header` and containing following content until the next `Header` of comparable level. If `number_sections` is true, a `number` attribute will be added to each `Header` containing the section number. If `base_level` is non-null, `Header` levels will be reorganized so that there are no gaps, and so that the base level is the level specified. Returns: - List of [Blocks](#Blocks). Usage: local blocks = { pandoc.Header(2, pandoc.Str 'first'), pandoc.Header(2, pandoc.Str 'second'), } local newblocks = pandoc.utils.make_sections(true, 1, blocks) ### run\_json\_filter {#utils-run_json_filter} `run_json_filter (doc, filter[, args])` Filter the given doc by passing it through the a JSON filter. Parameters: `doc`: : the Pandoc document to filter `filter`: : filter to run `args`: : list of arguments passed to the filter. Defaults to `{FORMAT}`. Returns: - ([Pandoc](#Pandoc)) Filtered document Usage: -- Assumes `some_blocks` contains blocks for which a -- separate literature section is required. local sub_doc = pandoc.Pandoc(some_blocks, metadata) sub_doc_with_bib = pandoc.utils.run_json_filter( sub_doc, 'pandoc-citeproc' ) some_blocks = sub_doc.blocks -- some blocks with bib ### normalize\_date {#utils-normalize_date} `normalize_date (date_string)` Parse a date and convert (if possible) to "YYYY-MM-DD" format. We limit years to the range 1601-9999 (ISO 8601 accepts greater than or equal to 1583, but MS Word only accepts dates starting 1601). Returns: - A date string, or nil when the conversion failed. ### sha1 {#utils-sha1} `sha1 (contents)` Returns the SHA1 has of the contents. Returns: - SHA1 hash of the contents. Usage: local fp = pandoc.utils.sha1("foobar") ### stringify {#utils-stringify} `stringify (element)` Converts the given element (Pandoc, Meta, Block, or Inline) into a string with all formatting removed. Returns: - A plain string representation of the given element. Usage: local inline = pandoc.Emph{pandoc.Str 'Moin'} -- outputs "Moin" print(pandoc.utils.stringify(inline)) ### to\_roman\_numeral {#utils-to_roman_numeral} `to_roman_numeral (integer)` Converts an integer \< 4000 to uppercase roman numeral. Returns: - A roman numeral string. Usage: local to_roman_numeral = pandoc.utils.to_roman_numeral local pandoc_birth_year = to_roman_numeral(2006) -- pandoc_birth_year == 'MMVI' # Module pandoc.mediabag The `pandoc.mediabag` module allows accessing pandoc's media storage. The "media bag" is used when pandoc is called with the `--extract-media` or (for HTML only) `--self-contained` option. The module is loaded as part of module `pandoc` and can either be accessed via the `pandoc.mediabag` field, or explicitly required, e.g.: local mb = require 'pandoc.mediabag' ### delete {#mediabag-delete} `delete (filepath)` Removes a single entry from the media bag. Parameters: `filepath`: : filename of the item to be deleted. The media bag will be left unchanged if no entry with the given filename exists. ### empty {#mediabag-empty} `empty ()` Clear-out the media bag, deleting all items. ### insert {#mediabag-insert} `insert (filepath, mime_type, contents)` Adds a new entry to pandoc's media bag. Parameters: `filepath`: : filename and path relative to the output folder. `mime_type`: : the file's MIME type `contents`: : the binary contents of the file. Usage: local fp = "media/hello.txt" local mt = "text/plain" local contents = "Hello, World!" pandoc.mediabag.insert(fp, mt, contents) ### items {#mediabag-items} `items ()` Returns an iterator triple to be used with Lua's generic `for` statement. The iterator returns the filepath, MIME type, and content of a media bag item on each invocation. Items are processed one-by-one to avoid excessive memory use. This function should be used only when full access to all items, including their contents, is required. For all other cases, [`list`](#mediabag-list) should be preferred. Returns: - The iterator function; must be called with the iterator state and the current iterator value. - Iterator state -- an opaque value to be passed to the iterator function. - Initial iterator value. Usage: for fp, mt, contents in pandoc.mediabag.items() do -- print(fp, mt, contents) end ### list {#mediabag-list} `list ()` Get a summary of the current media bag contents. Returns: A list of elements summarizing each entry in the media bag. The summary item contains the keys `path`, `type`, and `length`, giving the filepath, MIME type, and length of contents in bytes, respectively. Usage: -- calculate the size of the media bag. local mb_items = pandoc.mediabag.list() local sum = 0 for i = 1, #mb_items do sum = sum + mb_items[i].length end print(sum) ### lookup {#mediabag-lookup} `lookup (filepath)` Lookup a media item in the media bag, and return its MIME type and contents. Parameters: `filepath`: : name of the file to look up. Returns: - the entry's MIME type, or nil if the file was not found. - contents of the file, or nil if the file was not found. Usage: local filename = "media/diagram.png" local mt, contents = pandoc.mediabag.lookup(filename) ### fetch {#mediabag-fetch} `fetch (source, base_url)` Fetches the given source from a URL or local file. Returns two values: the contents of the file and the MIME type (or an empty string). Returns: - the entries MIME type, or nil if the file was not found. - contents of the file, or nil if the file was not found. Usage: local diagram_url = "https://pandoc.org/diagram.jpg" local mt, contents = pandoc.mediabag.fetch(diagram_url, ".") # Module pandoc.List Pandoc\'s List type and helper methods ## Metamethods [`pandoc.List:__concat (list)`]{#pandoc.List:__concat} : Concatenates two lists. Parameters: `list`: : second list concatenated to the first Returns: a new list containing all elements from list1 and list2 ## Methods [`pandoc.List:clone ()`]{#pandoc.List:clone} : Returns a (shallow) copy of the list. [`pandoc.List:includes (needle, init)`]{#pandoc.List:includes} : Checks if the list has an item equal to the given needle. Parameters: `needle`: : item to search for `init`: : index at which the search is started Returns: true if a list item is equal to the needle, false otherwise [`pandoc.List:find (needle, init)`]{#pandoc.List:find} : Returns the value and index of the first occurrence of the given item. Parameters: `needle`: : item to search for `init`: : index at which the search is started Returns: first item equal to the needle, or nil if no such item exists. [`pandoc.List:find_if (pred, init)`]{#pandoc.List:find_if} : Returns the value and index of the first element for which the predicate holds true. Parameters: `pred`: : the predicate function `init`: : index at which the search is started Returns: first item for which \`test\` succeeds, or nil if no such item exists. [`pandoc.List:extend (list)`]{#pandoc.List:extend} : Adds the given list to the end of this list. Parameters: `list`: : list to appended [`pandoc.List:map (fn)`]{#pandoc.List:map} : Returns a copy of the current list by applying the given function to all elements. Parameters: `fn`: : function which is applied to all list items. [`pandoc.List:filter (pred)`]{#pandoc.List:filter} : Returns a new list containing all items satisfying a given condition. Parameters: `pred`: : condition items must satisfy. Returns: a new list containing all items for which \`test\` was true. # Module pandoc.system Access to system information and functionality. ## Static Fields {#system-fields} ### arch {#system-arch} The machine architecture on which the program is running. ### os {#system-os} The operating system on which the program is running. ## Functions {#system-functions} ### environment {#system-environment} `environment ()` Retrieve the entire environment as a string-indexed table. Returns: - A table mapping environment variables names to their string value (table). ### get\_working\_directory {#system-get_working_directory} `get_working_directory ()` Obtain the current working directory as an absolute path. Returns: - The current working directory (string). ### with\_environment {#system-with_environment} `with_environment (environment, callback)` Run an action within a custom environment. Only the environment variables given by `environment` will be set, when `callback` is called. The original environment is restored after this function finishes, even if an error occurs while running the callback action. Parameters: `environment` : Environment variables and their values to be set before running `callback`. (table with string keys and string values) `callback` : Action to execute in the custom environment (function) Returns: - The result(s) of the call to `callback` ### with\_temporary\_directory {#system-with_temporary_directory} `with_temporary_directory ([parent_dir,] templ, callback)` Create and use a temporary directory inside the given directory. The directory is deleted after the callback returns. Parameters: `parent_dir` : Parent directory to create the directory in (string). If this parameter is omitted, the system's canonical temporary directory is used. `templ` : Directory name template (string). `callback` : Function which takes the name of the temporary directory as its first argument (function). Returns: - The result of the call to `callback`. ### with\_working\_directory {#system-with_working_directory} `with_working_directory (directory, callback)` Run an action within a different directory. This function will change the working directory to `directory`, execute `callback`, then switch back to the original working directory, even if an error occurs while running the callback action. Parameters: `directory` : Directory in which the given `callback` should be executed (string) `callback` : Action to execute in the given directory (function) Returns: - The result(s) of the call to `callback` # Module pandoc.types Constructors for types which are not part of the pandoc AST. ### Version {#pandoc.types.Version} `Version (version_specifier)` Creates a Version object. Parameters: `version`: : Version specifier: this can be a version string like `'2.7.3'`, a list of integers like `{2, 7, 3}`, a single integer, or a [Version](#type-ref-Version). Returns: - A new [Version](#type-ref-Version) object.