Learn Pod in Y Minutes

Pod is an easy-to-use and purely descriptive mark-up language, with no presentational components. Besides its use for documenting Raku programs and modules, Pod can be utilized to write language documentation, blogs, and other types of document composition as well.

Pod documents can be easily converted to HTML and many other formats (e.g., Markdown, Latex, plain text, etc.) by using the corresponding variant of the Pod::To modules (e.g. Pod::To::HTML for HTML conversion).

General Info
Pod Basics
Block Structures
Configuration Data
- Standard Configuration Options
- Block Pre-configuration
Semantic Blocks
Miscellaneous
Rendering Pod
Accessing Pod

General Info

Every Pod document has to begin with =begin pod and end with =end pod. Everything between these two delimiters will be processed and used to generate documentation.

=begin pod

A very simple Raku Pod document. All the other directives go here!

=end pod

Pod documents usually coexist with Raku code. If by themselves, Pod files often have the .pod6 suffix. Moving forward, it’s assumed that the constructs being discussed are surrounded by the =begin pod ... =end pod directives.

Pod Basics

Basic Text Formatting

Text can be easily styled as bold, italic, underlined or verbatim (for code formatting) using the following formatting codes: B<>, I<>, U<> and C<>.

B<This text is in Bold.>

I<This text is in Italics.>

U<This text is Underlined.>

The function C<sub sum { $^x + $^y}> is treated as verbatim.

There are more formatting codes (e.g., L<>, T<>, etc.) but they’ll be discussed later throughout the document. You’ll recognize them because they’re just a single capital letter followed immediately by a set of single or double angle brackets. The Unicode variant («») of the angle brackets can also be used.

Headings

Headings are created by using the =headN directive where N is the heading level.

=head1 This is level 1
=head2 This is level 2
=head3 This is level 3
=head4 This is level 4
=head5 This is level 5
=head6 This is level 6

Ordinary Paragraphs

Ordinary paragraphs consist of one or more adjacent lines of text, each of which starts with a non-whitespace character. Any paragraph is terminated by the first blank line or block directive.

=head1 First level heading block

=head2 Paragraph 1

This is an ordinary paragraph. Its text will be squeezed and
short lines filled. It is terminated by the first blank line.

=head2 Paragraph 2

This is another ordinary paragraph albeit shorter.

Alternatively, the =para directive can be used to explicitly mark adjacent lines of text as a paragraph.

=head1 First level heading block

=head2 Paragraph 1

=para
This is an ordinary paragraph. Its text will be squeezed and
short lines filled. It is terminated by the first blank line.

=head2 Paragraph 2

=para
This is another ordinary paragraph albeit shorter.

Lists

Unordered lists can be created using the =item directive.

=item Item
=item Item
=item Another item

Sublists are achieved with items at each level specified using the =item1, =item2, =item3, ..., =itemN etc. directives. The =item directive defaults to =item1.

=item1 Item one
=item1 Item two
=item1 Item three
    =item2 Sub-item
    =item2 Sub-item
=item1 Item four

Definition lists that define terms or commands use the =defn directive. This is equivalent to the <dl> element in HTML.

=defn Beast of Bodmin
A large feline inhabiting Bodmin Moor.

=defn Morgawr
A sea serpent.

=defn Owlman
A giant owl-like creature.

Code Blocks

A code block is created (which uses the HTML <code> element) by starting each line with one or more whitespace characters.

    #`( this is comment )
    my $sum = -> $x, $y { $x + $y }
    say $sum(12, 5);

As shown in the Basic Text Formatting section, inline code can be created using the C<> code.

In Raku, there are several functions/methods to output text. Some of them
are C<print>, C<put> and C<say>.

Comments

Although Pod blocks are ignored by the Rakudo Raku compiler, everything identified as a Pod block will be read and interpreted by Pod renderers. In order to prevent Pod blocks from being rendered by any renderer, use the =comment directive.

=comment Add more here about the algorithm.

=comment Pod comments are great for documenting the documentation.

To create inline comments, use the Z<> code.

Pod is awesome Z<Of course it is!>. And Raku too!

Given that the Raku interpreter never executes embedded Pod blocks, comment blocks can also be used as an alternative form of nestable block comments.

Links

Creating links in Pod is quite easy and is done by enclosing them in a L<> code. The general format is L<Label|Url> with Label being optional.

Raku homepage is L<https://raku.org>.
L<Click me!|http://link.org/>.

Relative paths work too.

L<Go to music|/music/>.

Linking to a section in the same document works as well.

L<Link to Headings|#Headings>

Tables

The Pod specifications are not completely handled properly yet and this includes the handling of table. For simplicity’s sake, only one way of constructing tables is shown here. To learn about good practices and see examples of both good and bad tables, please visit https://docs.raku.org/language/tables.

=begin table
Option      | Description     
============|================  
data        | path to data files.
engine      | engine to be used for processing templates.
ext         | extension to be used for dest files.
=end table

Block Structures

As mentioned earlier, Pod documents are specified using directives, which are used to delimit blocks of textual content and declare optional configuration information. Every directive starts with an equals sign (=) in the first column. The content of a document is specified within one or more blocks. Every Pod block may be declared in any of three equivalent forms: delimited style, paragraph style, or abbreviated style.

Up to this point, we have only used the abbreviated style for the block types (e.g., =head1, =para, =comment, =item, etc).

Abbreviated Blocks

Abbreviated blocks are introduced by an = sign in the first column, which is followed immediately by the typename of the block and then the content. The rest of the line is treated as block data, rather than as configuration. The content terminates at the next Pod directive or the first blank line (which is not part of the block data). The general syntax is

=BLOCK_TYPE  BLOCK_DATA

For example:

=head1 Top level heading

Delimited Blocks

Delimited blocks are bounded by =begin and =end markers, both of which are followed by a valid Pod identifier, which is the typename of the block. The general syntax is

=begin BLOCK_TYPE
BLOCK_DATA
=end BLOCK_TYPE

For example:

=begin head1
Top level heading
=end head1

This type of blocks is useful for creating headings, list items, code blocks, etc. with multiple paragraphs. For example,

a multiline item of a list

=begin item
This is a paragraph in list item.

This is another paragraph in the same list item.
=end item

a code block

=begin code
#`(
A non-efficient recursive implementation of a power function using multi subs.
)

multi pow( Real $base, 0 ) { 1 }

multi pow( Real $base, Int $exp where * ≥ 0) {
    $base * pow($base, $exp - 1)
}

multi pow( Real $base ) {
     pow($base, 2)
}

say pow(3, 0);   #=> 1
say pow(4.2, 2); #=> 17.64
say pow(6);      #=> 36
=end code

Paragraph Blocks

Paragraph blocks are introduced by a =for marker and terminated by the next Pod directive or the first blank line (which is not considered to be part of the block’s contents). The =for marker is followed by the typename of the block. The general syntax is

=for BLOCK_TYPE
BLOCK DATA

For example:

=for head1
Top level heading

Configuration Data

Except for abbreviated blocks, both delimited blocks and paragraph blocks can be supplied with configuration information about their contents right after the typename of the block. Thus the following are more general syntaxes for these blocks:

Delimited blocks

=begin BLOCK_TYPE OPTIONAL_CONFIG_INFO
=                 ADDITIONAL_CONFIG_INFO
BLOCK_DATA
=end BLOCK_TYPE

Paragraph blocks

=for BLOCK_TYPE OPTIONAL_CONFIG_INFO
=               ADDITIONAL_CONFIG_INFO
BLOCK DATA

The configuration information is provided in a format akin to the “colon pair” syntax in Raku. The following table is a simplified version of the different ways in which configuration info can be supplied. Please go to https://docs.raku.org/language/pod#Configuration_information for a more thorough treatment of the subject.

Value	Specify with…	Example
List	:key($elem1, $elem2, …)	:tags(‘Pod’, ‘Raku’)
Hash	:key{$key1 => $value1, …}	:feeds{url => ‘raku.org’}
Boolean	:key/:key(True)	:skip-test(True)
Boolean	:!key/:key(False)	:!skip-test
String	:key(‘string’)	:nonexec-reason(‘SyntaxError’)
Int	:key(2)	:post-number(6)

Standard Configuration Options

Pod provides a small number of standard configuration options that can be applied uniformly to built-in block types. Some of them are:

:numbered

This option specifies that the block is to be numbered. The most common use of this option is to create numbered headings and ordered lists, but it can be applied to any block.

For example:

=for head1 :numbered
The Problem
=for head1 :numbered
The Solution
=for head2 :numbered
Analysis
=for head3 :numbered
Overview

:allow

The value of the :allow option must be a list of the (single-letter) names of one or more formatting codes. Those codes will then remain active inside the code block. The option is most often used on =code blocks to allow mark-up within those otherwise verbatim blocks, though it can be used in any block that contains verbatim text.

Given the following snippet:

=begin code :allow('B', 'I')
B<sub> greet( $name ) {
    B<say> "Hello, $nameI<!>";
}
=end code

we get the following output:

sub greet( $name ) {
    say "Hello, $name!";
}

This is highly dependent on the format output. For example, while this works when Pod is converted to HTML, it might not be preserved when converted to Markdown.

Block Pre-configuration

The =config directive allows you to prespecify standard configuration information that is applied to every block of a particular type. The general syntax for configuration directives is:

=config BLOCK_TYPE  CONFIG OPTIONS
=                  ADDITIONAL_CONFIG_INFO

For example, to specify that every heading level 1 be numbered, bold and underlined, you preconfigure the =head1 as follows:

=config head1 :formatted('B', 'U') :numbered

Semantic Blocks

All uppercase block typenames are reserved for specifying standard documentation, publishing, source components, or meta-information. Some of them are:

=NAME
=AUTHOR
=VERSION
=CREATED
=SYNOPSIS
=DESCRIPTION
=USAGE

Most of these blocks would typically be used in their full delimited forms. For example,

=NAME B<Doc::Magic>

=begin DESCRIPTION
This module helps you generate documentation automagically.
Not source code needed! Most of it is outsourced from a black hole.
=end DESCRIPTION

=begin SYNOPSIS
=begin code
    use Doc::Magic;

    my Doc::Magic $doc .= new();

    my $result = $doc.create-documentation($fh);
=end code
=end SYNOPSIS

=AUTHOR Authorius Docus
=VERSION 42

Miscellaneous

Notes

Notes are rendered as footnotes and created by enclosing a note in a N<> code.

In addition, the language is also multi-paradigmatic N<According to Wikipedia,
this means that it supports procedural, object-oriented, and functional
programming.>

Keyboard Input

To flag text as keyboard input enclose it in a K<> code.

Enter your name K<John Doe>

Terminal Output

To flag text as terminal output enclose it in T<> code.

Hello, T<John Doe>

Unicode

To include Unicode code points or HTML5 character references in a Pod document, enclose them in a E<> code.

For example:

Raku makes considerable use of the E<171> and E<187> characters.
Raku makes considerable use of the E<laquo> and E<raquo> characters.

is rendered as:

Raku makes considerable use of the « and » characters. Raku makes considerable use of the « and » characters.

Rendering Pod

To generate any output (i.e., Markdown, HTML, Text, etc.), you need to have the Rakudo Raku compiler installed. In addition, you must install a module (e.g., Pod::To::Markdown, Pod::To::HTML, Pod::To::Text, etc.) that generates your desired output from Pod.

For instructions about installing Rakudo for running raku programs, look here.

Run the following command to generate a certain output:

raku --doc=TARGET input.pod6 > output.html

with TARGET being Markdown, HTML, Text, etc. Thus to generate Markdown from Pod, run this:

raku --doc=Markdown input.pod6 > output.html

Accessing Pod

In order to access Pod documentation from within a Raku program, it is required to use the special = twigil (e.g., $=pod, $=SYNOPSIS,etc).

The $= construct provides the introspection over the Pod structure, producing a Pod::Block tree root from which it is possible to access the whole structure of the Pod document.

If we place the following piece of Raku code and the Pod documentation in the section Semantic blocks in the same file:

my %used-directives;
for $=pod -> $pod-item {
    for $pod-item.contents -> $pod-block {
        next unless $pod-block ~~ Pod::Block::Named;
        %used-directives{$pod-block.name} = True;
    }
}

say %used-directives.keys.join("\n");

we get the following output:

SYNOPSIS
NAME
VERSION
AUTHOR
DESCRIPTION

Additional Information

https://docs.raku.org/language/pod for the Pod documentation.
https://docs.raku.org/language/tables for advices about Pod tables.
https://design.raku.org/S26.html for the Pod specification.

Got a suggestion? A correction, perhaps? Open an Issue on the GitHub Repo, or make a pull request yourself!

Originally contributed by Luis F. Uceta, and updated by 3 contributors.

Learn X in Y minutes

Where X=Pod

General Info

Pod Basics

Basic Text Formatting

Headings

Ordinary Paragraphs

Lists

Code Blocks

Comments

Links

Tables

Block Structures

Abbreviated Blocks

Delimited Blocks

Paragraph Blocks

Configuration Data

Standard Configuration Options

Block Pre-configuration

Semantic Blocks

Miscellaneous

Notes

Keyboard Input

Terminal Output

Unicode

Rendering Pod

Accessing Pod

Additional Information