Provided by: libpandoc-elements-perl_0.38-6_all 
NAME
Pandoc::Elements - create and process Pandoc documents
SYNOPSIS
The output of this script "hello.pl"
use Pandoc::Elements;
use JSON;
print Document(
{
title => MetaInlines [ Str "Greeting" ]
},
[
Header( 1, attributes { id => 'top' }, [ Str 'Hello' ] ),
Para [ Str 'Hello, world!' ],
],
api_version => '1.17.0.4'
)->to_json;
can be converted for instance to HTML via
./hello.pl | pandoc -f json -t html5 --standalone
an equivalent Pandoc Markdown document would be
% Greeting
# Gruss {.de}
Hello, world!
DESCRIPTION
Pandoc::Elements provides utility functions to parse, serialize, and modify abstract syntax trees (AST)
of Pandoc <http://pandoc.org/> documents. Pandoc can convert this data structure to many other document
formats, such as HTML, LaTeX, ODT, and ePUB.
See also module Pandoc::Filter, command line script pod2pandoc, and the internal modules Pandoc::Walker
and Pod::Simple::Pandoc.
PANDOC VERSIONS
The Pandoc document model is defined in file Text.Pandoc.Definition
<https://hackage.haskell.org/package/pandoc-types/docs/Text-Pandoc-Definition.html> as part of Haskell
package pandoc-types <https://hackage.haskell.org/package/pandoc-types>.
Pandoc::Elements is compatible with pandoc-types 1.12.3 (released with pandoc 1.12.1) up to
pandoc-types-1.21 (first released with pandoc 2.10). JSON output of all pandoc releases since 1.12.1 can
be parsed with function "pandoc_json", the "Document" constructor or method "parse" of module Pandoc. The
AST is always upgraded to pandoc-types 1.22 and downgraded to another api version on serialization with
"to_json".
To determine the api version required by a version of pandoc executable since version 1.18 execute pandoc
with the "--version" option and check which version of the "pandoc-types" library pandoc was compiled
with.
Beginning with version 1.18 pandoc will not decode a JSON AST representation unless the major and minor
version numbers (Document method "api_version") match those built into that version of pandoc. The
following changes in pandoc document model have been implemented:
• pandoc-types 1.22, released for pandoc 2.11, further modified representation the Table element.
• pandoc-types 1.21, released for pandoc 2.10, introduced the Underline element and modified
representation of the Table element.
• pandoc-types 1.17, released for pandoc 1.18, introduced the LineBlock element and modified
representation of the root Document element.
• pandoc-types 1.16, released with pandoc 1.16, introduced attributes to Link and Image elements
• pandoc-types 1.12.3, released with pandoc 1.12.1, modified the representation of elements to objects
with field "t" and "c". This is also the internal representation of documents used in this module.
FUNCTIONS
The following functions and keywords are exported by default:
• Constructors for all Pandoc document element (block elements such as "Para" and inline elements such
as "Emph", metadata elements and the Document).
• Type keywords such as "Decimal" and "LowerAlpha" to be used as types in other document elements.
• The following helper functions "pandoc_json", "pandoc_version", "attributes", "metadata", "citation",
and "element".
pandoc_json $json
Parse a JSON string, as emitted by pandoc in JSON format. This is the reverse to method "to_json" but it
can read both old (before Pandoc 1.16) and new format.
attributes { key => $value, ... }
Maps a hash reference or instance of Hash::MultiValue into the internal structure of Pandoc attributes.
The special keys "id" (string), and "class" (string or array reference with space-separated class names)
are recognized. See attribute methods for details.
citation { ... }
A citation as part of document element Cite must be a hash reference with fields "citationId" (string),
"citationPrefix" (list of inline elements) "citationSuffix" (list of inline elements), "citationMode"
(one of "NormalCitation", "AuthorInText", "SuppressAuthor"), "citationNoteNum" (integer), and
"citationHash" (integer). The helper method "citation" can be used to construct such a hash by filling in
default values and optionally using shorter field names ("id", "prefix", "suffix", "mode", "note", and
"hash"):
citation {
id => 'foo',
prefix => [ Str "see" ],
suffix => [ Str "p.", Space, Str "42" ]
}
# in Pandoc Markdown
[see @foo p. 42]
The values returned by this function, as well as any citations contained in document objects returned by
"pandoc_json", are blessed hashrefs with getter/setter accessors corresponding to both the full and short
field names, so that e.g. "$citation->citationId(...)" and "$citation->id(...)" get or set the same
value.
pandoc_version( [ $document ] )
Return a Pandoc::Version object with expected version number of pandoc executable to be used for
serializing documents with to_json.
If a Document element is given as argument, the minimal pandoc release version compatible with its api
version is returned.
Without argument, package variable $PANDOC_VERSION is checked for a preferred pandoc release. By default
this variable is set from an environment variable of same name. If no preferred pandoc release has been
specified, the function returns version 1.18 because this is the first pandoc release compatible with
most recent api version supported by this module.
See also method "version" of module Pandoc to get the current version of pandoc executable on your
system.
element( $name => $content )
Create a Pandoc document element of arbitrary name. This function is only exported on request.
ELEMENTS AND METHODS
Document elements are encoded as Perl data structures equivalent to the JSON structure, emitted with
pandoc output format "json". This JSON structure is subject to minor changes between versions of pandoc.
All elements are blessed objects that provide common element methods (all elements), attribute methods
(elements with attributes), and additional element-specific methods.
COMMON METHODS
to_json
Return the element as JSON encoded string. The following are equivalent:
$element->to_json;
JSON->new->utf8->canonical->convert_blessed->encode($element);
The serialization format can be adjusted to different pandoc versions with module and environment
variable "PANDOC_VERSION" or with Document element properties "api_version" and "pandoc_version".
When writing filters you can normally just rely on the api version value obtained from pandoc, since
pandoc expects to receive the same JSON format as it emits.
name
Return the name of the element, e.g. "Para" for a paragraph element.
content
Return the element content. For most elements (Para, Emph, Str...) the content is an array reference with
child elements. Other elements consist of multiple parts; for instance the Link element has attributes
("attr", "id", "class", "classes", "keyvals") a link text ("content") and a link target ("target") with
"url" and "title".
is_block
True if the element is a Block element
is_inline
True if the element is an inline Inline element
is_meta
True if the element is a Metadata element
is_document
True if the element is a Document element
as_block
Return the element unmodified if it is a block element or wrapped in a Plain or Div otherwise.
match( $selector )
Check whether the element matches a given Pandoc::Selector (given as instance or string).
walk(...)
Walk the element tree with Pandoc::Walker
query(...)
Query the element to extract results with Pandoc::Walker
transform(...)
Transform the element tree with Pandoc::Walker
string
Returns a concatenated string of element content, leaving out all formatting.
ATTRIBUTE METHODS
Some elements have attributes which can be an identifier, ordered class names and ordered key-value
pairs. Elements with attributes provide the following methods:
attr
Get or set the attributes in Pandoc internal structure:
[ $id, [ @classes ], [ [ key => $value ], ... ] ]
See helper function attributes to create this structure.
keyvals
Get all attributes (id, class, and key-value pairs) as new Hash::MultiValue instance, or replace all key-
value pairs plus id and/or class if these are included as field names. All class fields are split by
whitespaces.
$e->keyvals # return new Hash::MultiValue
$e->keyvals( $HashMultiValue ) # update by instance of Hash::MultiValue
$e->keyvals( key => $value, ... ) # update by list of key-value pairs
$e->keyvals( \%hash ) # update by hash reference
$e->keyvals( { } ) # remove all key-value pairs
$e->keyvals( id => '', class => '' ) # remove all key-value pairs, id, class
id
Get or set the identifier. See also Pandoc::Filter::HeaderIdentifiers for utility functions to handle
Header identifiers.
class
Get or set the list of classes, separated by whitespace.
add_attribute( $name => $value )
Append an attribute. The special attribute names "id" and "class" set or append identifier or class,
respectively.
DOCUMENT ELEMENT
Document
Root element, consisting of metadata hash ("meta"), document element array ("content"="blocks") and
optional "api_version". The constructor accepts either two arguments and an optional named parameter
"api_version":
Document { %meta }, [ @blocks ], api_version => $version_string
or a hash with three fields for metadata, document content, and an optional pandoc API version:
{
meta => { %metadata },
blocks => [ @content ],
pandoc-api-version => [ $major, $minor, $revision ]
}
The latter form is used as pandoc JSON format since pandoc release 1.18. If no api version is given, it
will be set to 1.21 which was also introduced with pandoc release 2.10.
A third ("old") form is accepted for compatibility with pandoc JSON format before release 1.18 and since
release 1.12.1: an array with two elements for metadata and document content respectively.
[ { unMeta => { %meta } }, [ @blocks ] ]
The api version is set to 1.16 in this case, but older versions down to 1.12.3 used the same format.
Document elements provide the following special methods in addition to common element methods:
api_version( [ $api_version ] )
Return the pandoc-types version (aka "pandoc-api-version") of this document as Pandoc::Version object
or sets it to a new value. This version determines how method to_json serializes the document.
See "PANDOC VERSIONS" for details.
pandoc_version( [ $pandoc_version ] )
Return the minimum required version of pandoc executable compatible with the api_version of this
document. The following are equivalent:
$doc->pandoc_version;
pandoc_version( $doc );
If used as setter, sets the api version of this document to be compatible with the given pandoc
version.
content or blocks
Get or set the array of block elements of the document.
meta( [ $metadata ] )
Get and/or set combined document metadata. Use method "value" to get selected metadata fields and
values.
value( [ $pointer ] [ %options ] )
Get selected document metadata field value(s). See Pandoc::Metadata for documentation. Can also be
called as "metavalue", so the following are equivalent:
$doc->value( ... );
$doc->meta->value( ... );
$doc->metavalue( ... );
to_pandoc( [ [ $pandoc, ] @arguments ])
Process the document with Pandoc executable and return its output:
$doc->to_pandoc( -o => 'doc.html' );
my $markdown = $doc->to_pandoc( -t => 'markdown' );
The first argument can optionally be an instance of Pandoc to use a specific executable.
to_...( [ @arguments ] )
Process the document into "markdown" (pandoc's extended Markdown), "latex" (LaTeX), "html" (HTML),
"rst" (reStructuredText), or "plain" (plain text). The following are equivalent:
$doc->to_markdown( @args );
$doc->to_pandoc( @args, '-t' => 'markdown' );
outline( [ $depth ] )
Returns an outline of the document structure based on Header elements. The outline is a hierarchical
hash reference with the following fields:
header
Header element (not included at the document root)
blocks
List of block elements before the next Header element (of given depth or less if a maximum depth
was given)
sections
List of subsections, each having the same outline structure.
BLOCK ELEMENTS
BlockQuote
Block quote, consisting of a list of blocks ("content")
BlockQuote [ @blocks ]
BulletList
Unnumbered list of items ("content"="items"), each a list of blocks
BulletList [ [ @blocks ] ]
CodeBlock
Code block (literal string "content") with attributes ("attr", "id", "class", "classes", "keyvals")
CodeBlock $attributes, $content
DefinitionList
Definition list, consisting of a list of pairs ("content"="items"), each a term ("term", a list of
inlines) and one or more definitions ("definitions", a list of blocks).
DefinitionList [ @definitions ]
# each item in @definitions being a pair of the form
[ [ @inlines ], [ @blocks ] ]
Div
Generic container of blocks ("content") with attributes ("attr", "id", "class", "classes", "keyvals").
Div $attributes, [ @blocks ]
Header
Header with "level" (integer), attributes ("attr", "id", "class", "classes", "keyvals"), and text
("content", a list of inlines).
Header $level, $attributes, [ @inlines ]
HorizontalRule
Horizontal rule
HorizontalRule
LineBlock
List of lines ("content"), each a list of inlines.
LineBlock [ @lines ]
This element was added in pandoc 1.18. Before it was represented Para elements with embedded LineBreak
elements. This old serialization form can be enabled by setting $PANDOC_VERSION package variable to a
lower version number.
Null
Nothing
Null
OrderedList
Numbered list of items ("content"="items"), each a list of blocks), preceded by list attributes (start
number, numbering style, and delimiter).
OrderedList [ $start, $style, $delim ], [ [ @blocks ] ]
Supported styles are "DefaultStyle", "Example", "Decimal", "LowerRoman", "UpperRoman", "LowerAlpha", and
"UpperAlpha".
Supported delimiters are "DefaultDelim", "Period", "OneParen", and "TwoParens".
Para
Paragraph, consisting of a list of Inline elements ("content").
Para [ $elements ]
Plain
Plain text, not a paragraph, consisting of a list of Inline elements ("content").
Plain [ @inlines ]
RawBlock
Raw block with "format" and "content" string.
RawBlock $format, $content
Table
Table, with "caption", column "alignments", relative column "widths" (0 = default), column "headers"
(each a list of blocks), and "rows" (each a list of lists of blocks).
Table [ @inlines ], [ @alignments ], [ @width ], [ @headers ], [ @rows ]
Possible alignments are "AlignLeft", "AlignRight", "AlignCenter", and "AlignDefault".
An example:
Table [Str "Example"], [AlignLeft,AlignRight], [0.0,0.0],
[[Plain [Str "name"]]
,[Plain [Str "number"]]],
[[[Plain [Str "Alice"]]
,[Plain [Str "42"]]]
,[[Plain [Str "Bob"]]
,[Plain [Str "23"]]]];
INLINE ELEMENTS
Cite
Citation, a list of "citations" and a list of inlines ("content"). See helper function citation to
construct citations.
Cite [ @citations ], [ @inlines ]
Code
Inline code, a literal string ("content") with attributes ("attr", "id", "class", "classes", "keyvals")
Code attributes { %attr }, $content
Emph
Emphasized text, a list of inlines ("content").
Emph [ @inlines ]
Image
Image with alt text ("content", a list of inlines) and "target" (list of "url" and "title") with
attributes ("attr", "id", "class", "classes", "keyvals").
Image attributes { %attr }, [ @inlines ], [ $url, $title ]
Serializing the attributes is disabled in api version less then 1.16.
LineBreak
Hard line break
LineBreak
Link
Hyperlink with link text ("content", a list of inlines) and "target" (list of "url" and "title") with
attributes ("attr", "id", "class", "classes", "keyvals").
Link attributes { %attr }, [ @inlines ], [ $url, $title ]
Serializing the attributes is disabled in api version less then 1.16.
Math
TeX math, given as literal string ("content") with "type" (one of "DisplayMath" and "InlineMath").
Math $type, $content
Note
Footnote or Endnote, a list of blocks ("content").
Note [ @blocks ]
Quoted
Quoted text with quote "type" (one of "SingleQuote" and "DoubleQuote") and a list of inlines ("content").
Quoted $type, [ @inlines ]
RawInline
Raw inline with "format" (a string) and "content" (a string).
RawInline $format, $content
SmallCaps
Small caps text, a list of inlines ("content").
SmallCaps [ @inlines ]
SoftBreak
Soft line break
SoftBreak
This element was added in pandoc 1.16 as a matter of editing convenience to preserve line breaks (as
opposed to paragraph breaks) from input source to output. If you are going to feed a document containing
"SoftBreak" elements to Pandoc < 1.16 you will have to set the package variable or environment variable
"PANDOC_VERSION" to 1.15 or below.
Space
Inter-word space
Space
Span
Generic container of inlines ("content") with attributes ("attr", "id", "class", "classes", "keyvals").
Span attributes { %attr }, [ @inlines ]
Str
Plain text, a string ("content").
Str $content
Strikeout
Strikeout text, a list of inlines ("content").
Strikeout [ @inlines ]
Strong
Strongly emphasized text, a list of inlines ("content").
Strong [ @inlines ]
Subscript
Subscripted text, a list of inlines ("content").
Supscript [ @inlines ]
Superscript
Superscripted text, a list of inlines ("content").
Superscript [ @inlines ]
Underline
Underlined text, a list of inlines ("content").
Underline [ @inlines ]
This element was added in pandoc 2.10. If you are going to feed a document containing "Underline"
elements to Pandoc < 2.10 you will have to set the package variable or environment variable
"PANDOC_VERSION" to 2.9 or below.
Table
Underlined text, a list of inlines ("content").
Underline [ @inlines ]
This element was added in pandoc 2.10. If you are going to feed a document containing "Underline"
elements to Pandoc < 2.10 you will have to set the package variable or environment variable
"PANDOC_VERSION" to 2.9 or below.
METADATA ELEMENTS
See Pandoc::Metadata for documentation of metadata elements "MetaBool", "MetaString", "MetaMap",
"MetaInlines", "MetaList", and "MetaBlocks".
Helper function "metadata" can be used to convert scalars, hash references, array references, and Pandoc
Inline/Block elements into metadata elements.
TYPE KEYWORDS
The following document elements are only as used as type keywords in other document elements:
• "SingleQuote", "DoubleQuote"
• "DisplayMath", "InlineMath"
• "AuthorInText", "SuppressAuthor", "NormalCitation"
• "AlignLeft", "AlignRight", "AlignCenter", "AlignDefault"
• "DefaultStyle", "Example", "Decimal", "LowerRoman", "UpperRoman", "LowerAlpha", "UpperAlpha"
• "DefaultDelim", "Period", "OneParen", "TwoParens"
SEE ALSO
Perl module Pandoc implements a wrapper around the pandoc executable.
Similar libraries in other programming languages are listed at
<https://github.com/jgm/pandoc/wiki/Pandoc-wrappers-and-interfaces>.
AUTHOR
Jakob Voss <jakob.voss@gbv.de>
CONTRIBUTORS
Benct Philip Jonsson <bpjonsson@gmail.com>
TakeAsk <https://github.com/TakeAsh>
COPYRIGHT AND LICENSE
Copyright 2014- Jakob Voss
GNU General Public License, Version 2
This module is heavily based on Pandoc by John MacFarlane.
perl v5.36.0 2023-01-02 Pandoc::Elements(3pm)