damian@conway.org>
Pod is an easy-to-use markup language with a simple, consistent underlying document object model. Pod can be used for writing language documentation, for documenting programs and modules, as well as for other types of document composition.
Pod is an evolution of Perl 5's Plain Ol' Documentation (POD) markup. Compared to POD, Perl 6's Pod is much more uniform, somewhat more compact, and considerably more expressive. The Pod dialect also differs in that it is a purely descriptive mark-up notation, with no presentational components.
Pod documents are specified using directives, which are used to declare configuration information and to delimit blocks of textual content. All Pod directives are considered to be special types of comments in Perl 6.
Every directive starts either with an equals sign (=) followed
immediately by an identifier [1], or with
#= followed immediately by whitespace or an opening bracket.
Directives that start with = can be indented like the code they
interleave, but their initial = must still be the first non-whitespace
character on their line. Directives that start with #= can be placed
anywhere that a Perl 6 comment can appear, though they are meaningful
only in a subset of those places; see #Declarator blocks.
An indented Pod block is considered to have a virtual left margin, determined by the indentation of its opening delimiter.
In other words, if a directive is indented from the left margin, the column at which the first character of its opening delimiter appears is thereafter considered the first column of the entire block's contents.
As with Perl 6 heredocs, the virtual margin treats leading tabs as
aligning to tabstops spaced every ($?TABSTOP // 8) characters.
The content of a document is specified within one or more blocks. Every Pod block may be declared in any of four forms:
delimited style, paragraph style, abbreviated style, or declarator style. The first three forms are all equivalent; the fourth is distinct.
Anything in a document that is neither a Pod directive nor contained
within a Pod block is treated as "ambient" material. Typically this
would be the source code of the program that the Pod is documenting. Pod
parsers still parse this text into the internal representation of the
file, representing it as a Pod6::Block::Ambient block. Renderers
will usually ignore such blocks, but see #Aliases.
In Perl 5's POD format, once a POD directive is encountered, the parser
considers everything that follows to be POD, until an explicit =cut
directive is encountered, at which point the parser flips back to
parsing ambient source code. The Perl 6 Pod format is different. All Pod
directives have a defined terminator and the Pod parser always reverts to
"ambient" at the end of each Pod directive or block. To cause the parser
to remain in Pod mode, you must enclose the desired Pod region in a
pod block:
=begin pod
=head1 A heading
This is Pod too. Specifically, this is a simple C<para> block
$this = pod('also'); # Specifically, a code block
=end pod
Delimited blocks are bounded by =begin and =end markers, both of
which are followed by a valid Perl 6 identifier, which is the
typename of the block. Typenames that are entirely lowercase (for
example: =begin head1) or entirely uppercase (for example: =begin
SYNOPSIS) are reserved.
After the typename, the rest of the =begin marker line is treated as
configuration information for the block. This information is used in
different ways by different types of blocks, but is always specified using
Perl6-ish option pairs. That is, any of:
Value is... Specify with... Or with... Or with... Boolean (true) C«:key» C«:key(1)» C«key => 1» Boolean (false) C«:!key» C«:key(0)» C«key => 0» String C«:key<str>» C«:key('str')» C«key => 'str'» List C«:key<1 2 3>» C«:key[1,2,3]» C«key => [1,2,3]»
All option keys and values must, of course, be constants since Pod is a specification language, not a programming language. Specifically, option values cannot be closures. See Synopsis 2 for details of the various Perl 6 pair notations.
The configuration section may be extended over subsequent lines by
starting those lines with an = in the first (virtual) column followed
by a whitespace character.
The lines following the opening delimiter and configuration are the
data or contents of the block, which continue until the block's matching
=end marker line. For most block types, these contents may be
indented if you wish, without them being treated as code blocks. Unlike Perl 5, indented text is only treated as code within
=pod, =nested, =item, =code,
and semantic blocks.
The general syntax is:
=begin BLOCK_TYPE OPTIONAL CONFIG INFO
= OPTIONAL EXTRA CONFIG INFO
BLOCK CONTENTS
=end BLOCK_TYPE
For example:
=begin table :caption<Table of Contents>
Constants 1
Variables 10
Subroutines 33
Everything else 57
=end table
=begin Name :required
= :width(50)
The applicant's full name
=end Name
=begin Contact :optional
The applicant's contact details
=end Contact
Note that no blank lines are required around the directives; blank lines within the contents are always treated as part of the contents. This is a universal feature of Pod.
Note also that in the following specifications, a "blank line" is a line
that is either empty or that contains only whitespace characters. That
is, a blank line matches the Perl 6 pattern: /^^ \h* $$/. Pod uses
blank lines as delimiters, rather than empty lines, to minimize unpleasant
surprises when stray spaces or tabs mysteriously turn up in hitherto
empty lines.
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 name of the block and optional configuration
information. The general syntax is:
=for BLOCK_TYPE OPTIONAL CONFIG INFO
= OPTIONAL EXTRA CONFIG INFO
BLOCK DATA
For example:
=for table :caption<Table of Contents>
Constants 1
Variables 10
Subroutines 33
Everything else 57
=for Name :required
= :width(50)
The applicant's full name
=for Contact :optional
The applicant's contact details
Abbreviated blocks are introduced by an '=' sign in the
first column, which is followed immediately by the typename of the
block. 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
MORE BLOCK DATA
For example:
=table
Constants 1
Variables 10
Subroutines 33
Everything else 57
=Name The applicant's full name
=Contact The applicant's contact details
Note that abbreviated blocks cannot specify configuration information. If
configuration is required, use a =for or =begin/=end instead.
The fourth form of Pod block differs from the first three in that it does not specify an explicit typename. Instead, it obtains its identity and purpose from the Perl 6 source code to which it is attached; specifically, from some nearby declarator.
Declarator blocks are introduced by a special Perl comment: #=, which
must be immediately followed by either by a space or an opening bracket.
If followed by a space, the block is terminated by the end of line; if
followed by one or more opening brackets, the block is terminated by
the matching sequence of closing brackets.
That is, declarator Pod blocks are syntactically like ordinary Perl 6 single-line comments and embedded comments. The general syntax is:
#= BLOCK DATA TO END OF LINE
#={ BLOCK DATA
MORE BLOCK DATA
}
except that the second form may use any valid Perl 6 bracket delimiter (including repeated opening brackets), as described in Synopsis 2.
Declarator Pod blocks must either precede or immediately follow a valid Perl 6 declarator, and are then said to be "attached" to it. They are primarily intended to simplify the documentation of code interfaces. For example:
#= Base class for comms necromancy hierarchy
class Magic::Necrotelecomnicon {
has $.elemental; #= Source of all power
has $!true_name; # Source of all self-protection (not documented)
method cast(Spell $s)
#= Initiate a specified spell normally
{
do_raw_magic($s);
}
method kast( #= Initiate a specified spell abnormally
Spell $s #= The spell to be abnormally initiated
) {
do_raw_magic($s, :alternative);
}
#= This subroutine does the real work
sub do_raw_magic (
Spell $s, #= Which spell to invoke
*%options #= How to invoke it
) {...}
}
Each declarator block is appended to the .WHY attribute of the
declared entity (object or type) whose declarator appeared at the
start of the nearest preceding line, provided that declarator is
"attached" to the Pod comment (i.e. it must not be separated from it
by an entirely blank line). That is:
my $chainsaw; #= This text stored in C<$chainsaw.WHY>
sub fu ( #= This text stored in C<&fu.WHY>
Any $bar, #= This text stored in C<$bar.WHY>
Mode :$baz, #= This text stored in C<$baz.WHY>
Context :$the_context_in_which_we_fu?
#= This stored in C<$the_context_in_which_we_fu.WHY>
) { ... }
sub fu2 (Any $bar)
#=[ This text stored in C<&fu2.WHY>, not in C<$bar.WHY>,
(because C<sub fu2> is the declarator
at the I<start> of the preceding line)
]
multi sub baz(Int $count, Str $name)
#=[ This text stored in C<&baz:(Int,Str).WHY>
(i.e. the C<.WHY> of the variant, not of the entire multisub)
]
If a declarator block is not immediately preceded by an attached line
that begins with a declarator, then the declarator block is instead
appended to the .WHY attribute of the next declarator encountered,
which must also begin at the next non-whitespace token. For example:
#= This text stored in C<$chainsaw.WHY>
my $chainsaw;
#=[ This text stored in C<&fu.WHY>
(because its delarator is the next non-ws token)
]
sub fu (Any $bar) {...}
Note that the second Pod comment in this example documents the &fu
that comes after it, not the $chainsaw preceding it, because it is
not "attached" to $chainsaw, being separated from it by a blank line.
In other words, Declarator blocks are assumed to document the declarator they immediately follow (i.e. without intervening blank lines), or if they don't immediately follow a declarator, to document the declarator they precede (regardless of intervening whitespace). This is intended to support and DWIM with most standard layout approaches for commenting and inline documention.
A declarator can have both a leading and a trailing Pod comment, in which case they are concatenated with an intermediate newline:
#= This is a special chainsaw
my SwissArmy $chainsaw #= (It has a rocket launcher)
say $chainsaw.WHY; # prints: This is a special chainsaw
# (It has a rocket launcher)
The Pod object representing each Declarator block is still appended to
the current surrounding Pod object (e.g. to $=POD at the top level).
Each such block representation is an object of class
Pod6::Block::Declarator, and has a .WHEREFORE method that returns
the code object or metaobject created by the declarator to which the
documentation is attached.
When the default DOC INIT block
renders these Pod objects, it automatically includes information about
the declarator as well. For instance, the earlier Necrotelecomnicon
example might produce something like:
Name: Magic::Necrotelecomnicon:
Desc: Base class for comms necromancy hierarchy
Attrs:
.elemental : Source of all power
Methods:
.cast(Spell $s) : Initiate a specified spell normally
.kast(Spell $s) : Initiate a specified spell abnormally
Subroutines:
do_raw_magic( : This subroutine does the real work
Spell $s, : Which spell to invoke
*%options : How to invoke it
)
Note, however, that the exact rendering used for declarator blocks is
implementation dependent, and may also be pre-empted explicitly by some
DOC configuration statement
within the document, such as:
DOC use Pod6::Markovian;
or:
DOC INIT {
use Pod6::Eiffelish::Long;
say eiffelish_long($=POD);
exit;
}
The first three block specifications (delimited, paragraph, and abbreviated) are treated identically by the underlying documentation model, so you can use whichever form is most convenient for a particular documentation task. In the descriptions that follow, the abbreviated form will generally be used, but should be read as standing for all three forms equally.
For example, although #Headings shows only:
=head1 Top Level Heading
this automatically implies that you could also write that block as:
=for head1
Top Level Heading
or:
=begin head1
Top Level Heading
=end head1
Declarator blocks are distinct from these three forms. They do not have typenames of their own, but rather take their meaning and identity from the declared object or type to which they are attached. In general, they are used specifically to describe that declarand.
Pod predefines a small number of standard configuration options that can be applied uniformly to any built-in block type. These include:
:nested
This option specifies that the block is to be nested within its current
context. For example, nesting might be applied to block quotes, to textual
examples, or to commentaries. In addition the =code,
=item, =input, and =output
blocks all have implicit nesting.
Nesting of blocks is usually rendered by adding extra indentation to the block contents, but may also be indicated in other ways: by boxing the contents, by changing the font or size of the nested text, or even by folding the text (so long as a visible placeholder is provided).
Occasionally it is desirable to nest content by more than one level:
=begin para :nested
=begin para :nested
=begin para :nested
"We're going deep, deep, I<deep> undercover!"
=end para
=end para
=end para
:nested option a positive integer
value:
=begin para :nested(3)
"We're going deep, deep, I<deep> undercover!"
=end para
=comment Don't nest this code block in the usual way...
=begin code :nested(0)
1 2 3 4 5 6
123456789012345678901234567890123456789012345678901234567890
|------|-----------------------|---------------------------|
line instruction comments
number code
=end code
:!nested could also be used for this purpose:
=Z<>begin code :!nested
:numberedThis 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.
The numbering conventions for headings and lists are specified in those sections, but it is up to individual renderers to decide how to display any numbering associated with other types of blocks.
Note that numbering is never explicit; it is always implied by context.
:formattedThis option specifies that the contents of the block should be treated as if they had one or more formatting codes placed around them.
For example, instead of:
=for comment
The next para is both important and fundamental,
so doubly emphasize it...
=begin para
B<I<
Warning: Do not immerse in water. Do not expose to bright light.
Do not feed after midnight.
>>
=end para
=begin para :formatted<B I>
Warning: Do not immerse in water. Do not expose to bright light.
Do not feed after midnight.
=end para
The internal representations of these two versions are exactly the same,
except that the second one retains the :formatted option information
as part of the resulting block object.
Like all formatting codes, codes applied via a :formatted are
inherently cumulative. For example, if the block itself is already
inside a formatting code, that formatting code will still apply, in
addition to the extra "basis" and "important" formatting specified by
:formatted<B I>.
:like =config head2 :like<head1> :formatted<I>
=config Subhead :like<head2>
:allowV<> codes that appear in (or are implicitly applied to)
the current 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. See #Formatting.
:margin= of the opening block-delimiter occurs. For example:
=head1 Indenting Pod blocks
=begin para
This text is flush with the (virtual) left margin of
the Pod block because that margin is implicitly specified
by the C<=> of the C<=begin>
=end para
:margin option it is possible to specify a
character that acts like an explicit margin when it occurs as the first
non-whitespace character on any line within the block. For example:
=head1 Indenting Pod blocks
=begin para :margin<|>
|This text is flush with the (virtual) left margin of
|the Pod block because that margin is explicitly marked
|by the C<|>, as specified by the block's C<:margin<|>> option.
=end para
sub foo {
V<=begin> pod :margin<|>
|=head1 Hey Look: Indented Pod!
|
|You can indent Pod in Perl 6
|which makes code look cleaner
|when documentation is interspersed
|
| my $this is Code;
|
|=end pod
...
}
When a :margin option is used, each subsequent line (until the
corresponding closing delimiter is encountered) simply has any text matching
/^^ \s* $margin_char/ automatically removed. This may include a line that
then becomes the closing delimiter, as in the above example.
Any line from which such a margin marker is removed automatically resets the implicit margin for subsequent lines of the block, setting it to the length of the "marginalized" indent that was just removed. This implicit margin is then used until the next line with an explicit margin marker is encountered, or the block terminates.
Pod offers notations for specifying a wide range of standard block types...
Pod provides an unlimited number of levels of heading, specified by the
=headN block marker. For example:
=head1 A Top Level Heading
=head2 A Second Level Heading
=head3 A third level heading
=head86 A "Missed it by I<that> much!" heading
While Pod parsers are required to recognize and distinguish all levels of heading, Pod renderers are only required to provide distinct renderings of the first four levels of heading (though they may, of course, provide more than that). Headings at levels without distinct renderings would typically be rendered like the lowest distinctly rendered level.
You can specify that a heading is numbered using the :numbered option. For
example:
=for head1 :numbered
The Problem
=for head1 :numbered
The Solution
=for head2 :numbered
Analysis
=for head3
Overview
=for head3
Details
=for head2 :numbered
Design
=for head1 :numbered
The Implementation
which would produce:
1. The Problem
2. The Solution
2.1. Analysis
Overview
Details
2.2: Design
3. The Implementation
It is usually better to preset a numbering scheme for each heading level, in a series of configuration blocks:
=config head1 :numbered
=config head2 :numbered
=config head3 :!numbered
=head1 The Problem
=head1 The Solution
=head2 Analysis
=head3 Overview
=head3 Details
=head2 Design
=head1 The Implementation
Alternatively, as a short-hand, if the first whitespace-delimited word
in a heading consists of a single literal # character, the # is
removed and the heading is treated as if it had a :numbered option:
=head1 # The Problem
=head1 # The Solution
=head2 # Analysis
=head3 Overview
=head3 Details
=head2 # Design
=head1 # The Implementation
Note that, even though renderers are not required to distinctly render more than the first four levels of heading, they are required to correctly honour arbitrarily nested numberings. That is:
=head6 # The Rescue of the Kobayashi Maru
should produce something like:
2.3.8.6.1.9. The Rescue of the Kobayashi Maru
Ordinary paragraph blocks consist of text that is to be formatted into a document at the current level of nesting, with whitespace squeezed, lines filled, and any special inline mark-up applied.
Ordinary paragraphs consist of one or more consecutive lines of text, each of which starts with a non-whitespace character at (virtual) column 1. The paragraph is terminated by the first blank line or block directive. For example:
=head1 This is a heading block
This is an ordinary paragraph.
Its text will be squeezed and
short lines filled. It is terminated by
the first blank line.
This is another ordinary paragraph.
Its text will also be squeezed and
short lines filled. It is terminated by
the trailing directive on the next line.
=head2 This is another heading block
This is yet another ordinary paragraph,
at the first virtual column set by the
previous directive
Within a =pod, =item, =defn, =nested, =END, or
semantic block, ordinary paragraphs do not require
an explicit marker or delimiters, but there is also an explicit para
marker (which may be used anywhere):
=para
This is an ordinary paragraph.
Its text will be squeezed and
short lines filled.
and likewise the longer =for and =begin/=end forms. For example:
=begin para
This is an ordinary paragraph.
Its text will be squeezed and
short lines filled.
This is I<still> part of the same paragraph,
which continues until an...
=end para
As the previous example implies, when any form of explicit para block
is used, any whitespace at the start of each line is removed during rendering.
In addition, within a delimited =begin para/=end para block, any
blank lines are preserved.
Code blocks are used to specify pre-formatted text (typically source code), which should be rendered without rejustification, without whitespace-squeezing, and without recognizing any inline formatting codes. Code blocks also have an implicit nesting associated with them. Typically these blocks are used to show examples of code, mark-up, or other textual specifications, and are rendered using a fixed-width font.
A code block may be implicitly specified as one or more lines of text, each of which starts with a whitespace character at the block's virtual left margin. The implicit code block is then terminated by a blank line. For example:
This ordinary paragraph introduces a code block:
$this = 1 * code('block');
$which.is_specified(:by<indenting>);
Implicit code blocks may only be used within =pod, =item, =defn,
=nested, =END, or semantic blocks.
There is also an explicit =code block (which can be specified within
any other block type, not just =pod, =item, etc.):
The C<loud_update()> subroutine adds feedback:
=begin code
sub loud_update ($who, $status) {
say "$who -> $status";
silent_update($who, $status);
}
=end code
As the previous example demonstrates, within an explicit =code block
the code can start at the (virtual) left margin. Furthermore, lines that
start with whitespace characters after that margin have subsequent
whitespace preserved exactly (in addition to the implicit nesting of the
code). Explicit =code blocks may also contain empty lines.
Although =code blocks automatically disregard all formatting
codes, occasionally you may still need to specify
some formatting within a code block. For example, you may wish
to emphasize a particular keyword in an example (using a B<> code). Or
you may want to indicate that part of the example is metasyntactic
(using the R<> code). Or you might need to insert a non-ASCII
character (using the E<> code).
You can specify a list of formatting codes that should still be
recognized within a code block using the :allow option. 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. For example:
=begin code :allow< B R >
sub demo {
B<say> 'Hello R<name>';
}
=end code
would be rendered:
sub demo {
say 'Hello name';
}
Note that the use of the :allow option also makes it possible
for verbatim formatting codes (such as C<>
and V<>) to contain other codes as well.
Pod also provides blocks for specifying the input and output of programs.
The =input block is used to specify pre-formatted keyboard input,
which should be rendered without rejustification or squeezing of whitespace.
The =output block is used to specify pre-formatted terminal or file
output which should also be rendered without rejustification or
whitespace-squeezing.
Note that, like =code blocks, both =input and =output blocks have an
implicit level of nesting. They are also like =code blocks in that they
are typically rendered in a fixed-width font, though ideally all three blocks
would be rendered in distinct font/weight combinations (for example: regular
serifed for code, bold sans-serif for input, and regular sans-serif for
output).
Unlike =code blocks, both =input and =output blocks honour any
nested formatting codes. This is particularly useful since a sample of
input will often include prompts (which are, of course, output).
Likewise a sample of output may contain the occasional interactive
component. Pod provides special formatting codes
(K<> and T<>) to indicate embedded input or output, so you can use
the block type that indicates the overall purpose of the sample (i.e. is
it demonstrating an input operation or an output sequence?) and then use
the "contrasting" formatting code within the block.
For example, to include a small amount of input in a sample of output
you could use the K<> formatting code:
=begin output
Name: Baracus, B.A.
Rank: Sgt
Serial: 1PTDF007
Do you want additional personnel details? K<y>
Height: 180cm/5'11"
Weight: 104kg/230lb
Age: 49
Print? K<n>
=end output
Lists in Pod are specified as a series of contiguous =item blocks. No
special "container" directives or other delimiters are required to
enclose the entire list. For example:
The seven suspects are:
=item Happy
=item Dopey
=item Sleepy
=item Bashful
=item Sneezy
=item Grumpy
=item Keyser Soze
List items have one implicit level of nesting:
The seven suspects are:
- Happy
- Dopey
- Sleepy
- Bashful
- Sneezy
- Grumpy
- Keyser Soze
Lists may be multi-level, with items at each level specified using the
=item1, =item2, =item3, etc. blocks. Note that =item is just
an abbreviation for =item1. For example:
=item1 Animal
=item2 Vertebrate
=item2 Invertebrate
=item1 Phase
=item2 Solid
=item2 Liquid
=item2 Gas
=item2 Chocolate
which would be rendered something like:
• Animal
– Vertebrate
– Invertebrate
• Phase
– Solid
– Liquid
– Gas
– Chocolate
Pod parsers must issue a warning if a "level-N+1" =item block
(e.g. an =item2, =item3, etc.) appears anywhere except where there
is a preceding "level-N" =item in the same surrounding block. That
is, an =item3 should only be specified if an =item2 appears
somewhere before it, and that =item2 should itself only appear if
there is a preceding =item1.
Note that item blocks within the same list are not physically nested. That is, lower-level items should not be specified inside higher-level items:
=comment WRONG...
=begin item1 --------------
The choices are: |
=item2 Liberty ==< Level 2 |==< Level 1
=item2 Death ==< Level 2 |
=item2 Beer ==< Level 2 |
=end item1 --------------
=comment CORRECT...
=begin item1 ---------------
The choices are: |==< Level 1
=end item1 ---------------
=item2 Liberty ==================< Level 2
=item2 Death ==================< Level 2
=item2 Beer ==================< Level 2
An item is part of an ordered list if the item has a :numbered
configuration option:
=for item1 :numbered
Visito
=for item2 :numbered
Veni
=for item2 :numbered
Vidi
=for item2 :numbered
Vici
This would produce something like:
1. Visito
1.1. Veni
1.2. Vidi
1.3. Vici
although the numbering scheme is entirely at the discretion of the renderer, so it might equally well be rendered:
1. Visito
1a. Veni
1b. Vidi
1c. Vici
or even:
A: Visito
(i) Veni
(ii) Vidi
(iii) Vici
Alternatively, if the first word of the item consists of a single #
character, the item is treated as having a :numbered option:
=item1 # Visito
=item2 # Veni
=item2 # Vidi
=item2 # Vici
To specify an unnumbered list item that starts with a literal #, either
make the octothorpe verbatim:
=item V<#> introduces a comment
or explicitly mark the item itself as being unnumbered:
=for item :!numbered
# introduces a comment
The numbering of successive =item1 list items increments
automatically, but is reset to 1 whenever any other kind of non-ambient
Pod block appears between two =item1 blocks. For example:
The options are:
=item1 # Liberty
=item1 # Death
=item1 # Beer
The tools are:
=item1 # Revolution
=item1 # Deep-fried peanut butter sandwich
=item1 # Keg
would produce:
The options are:
1. Liberty
2. Death
3. Beer
The tools are:
1. Revolution
2. Deep-fried peanut butter sandwich
3. Keg
The numbering of nested items (=item2, =item3, etc.) only resets
(to 1) when the higher-level item's numbering either resets or increments.
To prevent a numbered =item1 from resetting after a non-item block,
you can specify the :continued option:
=for item1
# Retreat to remote Himalayan monastery
=for item1
# Learn the hidden mysteries of space and time
I<????>
=for item1 :continued
# Prophet!
which produces:
1. Retreat to remote Himalayan monastery
2. Learn the hidden mysteries of space and time
????
3. Prophet!
List items that are not :numbered are treated as defining unordered
lists. Typically, such lists are rendered with bullets. For example:
=item1 Reading
=item2 Writing
=item3 'Rithmetic
might be rendered:
• Reading
— Writing
¤ 'Rithmetic
As with numbering styles, the bulleting strategy used for different levels within a nested list is entirely up to the renderer.
Use the delimited form of the =item block to specify items that
contain multiple paragraphs. For example:
Let's consider two common proverbs:
=begin item :numbered
I<The rain in Spain falls mainly on the plain.>
This is a common myth and an unconscionable slur on the Spanish
people, the majority of whom are extremely attractive.
=end item
=begin item :numbered
I<The early bird gets the worm.>
In deciding whether to become an early riser, it is worth
considering whether you would actually enjoy annelids
for breakfast.
=end item
As you can see, folk wisdom is often of dubious value.
which produces:
Let's consider two common proverbs:
The rain in Spain falls mainly on the plain.
This is a common myth and an unconscionable slur on the Spanish people, the majority of whom are extremely attractive.
The early bird gets the worm.
In deciding whether to become an early riser, it is worth considering whether you would actually enjoy annelids for breakfast.
As you can see, folk wisdom is often of dubious value.
To create term/definition lists, use a =defn block. This is
similar in effect to an =item block, in that a series of =defn
blocks implicitly defines a list (but which might then be rendered into
HTML using C«<DL>...</DL>» tags, rather than C«<UL>...</UL>» tags)
The first non-blank line of content is treated as a term being defined, and the remaining content is treated as the definition for the term. For example:
=defn MAD
Affected with a high degree of intellectual independence.
=defn MEEKNESS
Uncommon patience in planning a revenge that is worth while.
=defn
MORAL
Conforming to a local and mutable standard of right.
Having the quality of general expediency.
Like other kinds of list items, definitions can be numbered, using either an
option or a leading #:
=for defn :numbered
SELFISH
Devoid of consideration for the selfishness of others.
=defn # SUCCESS
The one unpardonable sin against one's fellows.
Any block can be nested by specifying a :nested option on it:
=begin para :nested
We are all of us in the gutter,E<NL>
but some of us are looking at the stars!
=end para
However, qualifying each nested paragraph individually quickly becomes tedious if there are many in a sequence, or if multiple levels of nesting are required:
=begin para :nested
We are all of us in the gutter,E<NL>
but some of us are looking at the stars!
=end para
=begin para :nested(2)
-- Oscar Wilde
=end para
So Pod provides a =nested block that marks all its contents as being
nested:
=begin nested
We are all of us in the gutter,E<NL>
but some of us are looking at the stars!
=begin nested
-- Oscar Wilde
=end nested
=end nested
Nesting blocks can contain any other kind of block, including implicit paragraph and code blocks. Note that the relative physical indentation of the blocks plays no role in determining their ultimate nesting. The preceding example could equally have been specified:
=begin nested
We are all of us in the gutter,E<NL>
but some of us are looking at the stars!
=begin nested
-- Oscar Wilde
=end nested
=end nested
Simple tables can be specified in Pod using a =table block.
The table may be given an associated description or title using the
:caption option.
Columns are separated by two or more consecutive whitespace characters,
or by a vertical line (|) or a border intersection (+), either of
which must be separated from any content by at least one whitespace
character.
Rows can be specified in one of two ways: either one row per line, with
no separators; or multiple lines per row with explicit horizontal
separators (whitespace, intersections (+), or horizontal lines: -,
=, _) between every row. Either style can also have an
explicitly separated header row at the top.
Each individual table cell is separately formatted, as if it were a
nested =para.
This means you can create tables compactly, line-by-line:
=table
The Shoveller Eddie Stevens King Arthur's singing shovel
Blue Raja Geoffrey Smith Master of cutlery
Mr Furious Roy Orson Ticking time bomb of fury
The Bowler Carol Pinnsler Haunted bowling ball
or line-by-line with multi-line headers:
=table
Superhero | Secret |
| Identity | Superpower
==============|=================|================================
The Shoveller | Eddie Stevens | King Arthur's singing shovel
Blue Raja | Geoffrey Smith | Master of cutlery
Mr Furious | Roy Orson | Ticking time bomb of fury
The Bowler | Carol Pinnsler | Haunted bowling ball
or with multi-line headers and multi-line data:
=begin table :caption('The Other Guys')
Secret
Superhero Identity Superpower
============= =============== ===================
The Shoveller Eddie Stevens King Arthur's
singing shovel
Blue Raja Geoffrey Smith Master of cutlery
Mr Furious Roy Orson Ticking time bomb
of fury
The Bowler Carol Pinnsler Haunted bowling ball
=end table
Blocks whose names contain at least one uppercase and one lowercase letter are assumed to be destined for specialized renderers or parser plug-ins. For example:
=begin Xhtml
<object type="video/quicktime" data="onion.mov">
=end Xhtml
or:
=Image http://www.perlfoundation.org/images/perl_logo_32x104.png
Named blocks are converted by the Pod parser to block objects;
specifically, to objects of a subclass of the standard
Pod6::Block::Named class.
For example, the blocks of the previous example would be converted to
objects of the classes Pod6::Block::Named::Xhtml and
Pod6::Block::Named::Image respectively. Both of those classes
would be automatically created as subclasses of the
Pod6::Block::Named class (unless they were already defined in a module
loaded via some prior DOC use.
The resulting object's .typename method retrieves the short name of
the block type: 'Xhtml', 'Image', etc. The object's .config
method retrieves the list of configuration options (if any). The
object's .contents method retrieves a list of the block's
verbatim contents.
Named blocks for which no explicit class has been defined or loaded are usually not rendered by the standard renderers.
Note that all block names consisting entirely of lowercase or entirely of uppercase letters are reserved. See #Semantic blocks.
All Pod blocks are intrinsically Perl 6 comments, but
Pod comments are comments that Pod renderers ignore too.
That is, they are Pod blocks that are never to be rendered by any
renderer. They are, of course, still included in any internal Pod
representation, and are accessible via the Pod API...and via the
$=POD variable within a Perl 6 program.
Comments are useful for meta-documentation (documenting the documentation):
=comment Add more here about the algorithm
and for temporarily removing parts of a document:
=item # Retreat to remote Himalayan monastery
=item # Learn the hidden mysteries of space and time
=item # Achieve enlightenment
=begin comment
=item # Prophet!
=end comment
Note that, since the Perl interpreter never executes embedded Pod
blocks, comment blocks can also be used as an alternative form of
nestable block comments in Perl 6:
=begin comment
for my $file (@files) {
system("rm -rf $file");
}
=end comment
=END block
The =END block is special in that all three of its forms
(delimited, paragraph, and
abbreviated) are terminated only by the end of the
current file. That is, neither =END nor =for END are terminated by the
next blank line, and =end END has no effect within a =begin END block.
A warning is issued if an explicit =end END appears within a document.
An =END block indicates the end-point of any ambient material within
the document. This means that the parser will treat all the remaining
text in the file as Pod, even if it is not inside an explicit block. In
other words, apart from its special end-of-file termination behaviour,
an =END block is in all other respects identical to a =pod block.
Named Pod blocks whose typename is DATA are the Perl 6 equivalent of
the Perl 5 __DATA__ section. The difference is that =DATA blocks are
just regular Pod blocks and may appear anywhere within a source file, and as
many times as required. Synopsis 2 describes the new Perl 6 interface
for accessing inline data of this type.
=DATA blocks are never rendered by the standard Pod renderers.
All uppercase block typenames except =END and =DATA are reserved
for specifying standard documentation, publishing, or source components.
In particular, all the standard components found in Perl and manpage
documentation have reserved uppercase typenames.
Standard semantic blocks include:
=NAME
=VERSION
=SYNOPSIS
=DESCRIPTION
=USAGE
=INTERFACE
=METHOD
=SUBROUTINE
=OPTION
=DIAGNOSTIC
=ERROR
=WARNING
=DEPENDENCY
=BUG
=SEE-ALSO
=ACKNOWLEDGEMENT
=AUTHOR
=COPYRIGHT
=DISCLAIMER
=LICENCE
=LICENSE
=TITLE
=SECTION
=CHAPTER
=APPENDIX
=TOC
=INDEX
=FOREWORD
=SUMMARY
The plural forms of each of these keywords are also reserved, and are aliases for the singular forms.
Most of these blocks would typically be used in their full delimited forms:
=begin SYNOPSIS
use Magic::Parser
my Magic::Parser $parser .= new();
my $tree = $parser.parse($fh);
=end SYNOPSIS
Semantic blocks can be considered to be variants of the =head1 block
in most respects (and most renderers will treat them as such). The main
difference is that, in a =head1 block, the heading is the contents of
the block; whereas, in a semantic block, the heading is derived from the
typename of the block itself and the block contents are instead treated as
the =para or =code block(s) belonging to the heading.
The use of these special blocks is not required; you can still just write:
=head1 SYNOPSIS
=begin code
use Magic::Parser
my Magic::Parser $parser .= new();
my $tree = $parser.parse($fh);
=end code
However, using the keywords adds semantic information to the
documentation, which may assist various renderers, summarizers, coverage
tools, document refactorers, and other utilities. This is because a
semantic block encloses the text it controls (unlike a =head1,
which merely precedes its corresponding text), so using semantic blocks
produces a more explicitly structured document.
Note that there is no requirement that semantic blocks be rendered in
a particular way (or at all). Specifically, it is not necessary to
preserve the capitalization of the keyword. For example, the
=SYNOPSIS block of the preceding example might be rendered like so:
3. Synopsis
use Perl6::Magic::Parser; my $rep = Perl6::Magic::Parser.parse($fh, :all_pod);
Formatting codes provide a way to add inline mark-up to a piece of text within the contents of (most types of) Pod block (including all declarator blocks). Formatting codes are themselves a type of block, and may nest other formatting codes. other type of block (most often, other formatting codes). In particular, you can nest comment blocks in the middle of a formatting code:
B<I shall say this loudly
Z<and repeatedly>
and with emphasis.>
All Pod formatting codes consist of a single capital letter followed
immediately by a set of angle brackets. The brackets contain the text or
data to which the formatting code applies. You can use a set of single
angles (C«<...>»), a set of double angles («...»), or multiple
single-angles (C«<<<...>>>»).
Within angle delimiters, you cannot use sequences of the same angle characters that are longer than the delimiters:
=comment
These are errors...
C< $fooB«<<»barB«>>» >
The Perl 5 heredoc syntax was: C< B«<<»END_MARKER >
You can use sequences of angles that are the same length as the delimiters, but they must be balanced. For example:
C< $foo<bar> >
C<< $foo<<bar>> >>
If you need an unbalanced angle, either use different delimiters:
C«$foo < $bar»
The Perl 5 heredoc syntax was: C« <<END_MARKER »
or delimiters with more consecutive angles than your text contains:
CB«<<»$foo < $barB«>>»
The Perl 5 heredoc syntax was: CB«<<<» <<END_MARKER B«>>>»
A formatting code ends at the matching closing angle bracket(s), or at the end of the enclosing block or formatting code in which the opening angle bracket was specified, whichever comes first (this includes paragraph and abbreviated blocks, ending with blank a line). Pod parsers are required to issue a warning whenever a formatting code is terminated by the end of an outer block rather than by its own delimiter (unless the user explicitly disables the warning).
Pod provides three formatting codes that flag their contents with increasing levels of significance:
U<> formatting code specifies that the contained text is
unusual or distinctive; that it is of minor significance. Typically
such content would be rendered in an underlined style.
I<> formatting code specifies that the contained text is
important; that it is of major significance. Such content would
typically be rendered in italics or in <em...<em/> > tags
B<> formatting code specifies that the contained text is the
basis or focus of the surrounding text; that it is of fundamental
significance. Such content would typically be rendered in a bold style or
in <strong...</strong> > tags.
The D<> formatting code indicates that the contained text is a
definition, introducing a term that the adjacent text
elucidates. It is the inline equivalent of a =defn block.
For example:
There ensued a terrible moment of D<coyotus interruptus>: a brief
suspension of the effects of gravity, accompanied by a sudden
to-the-camera realisation of imminent downwards acceleration.
A definition may be given synonyms, which are specified after a vertical bar and separated by semicolons:
A D<formatting code|formatting codes;formatters> provides a way
to add inline mark-up to a piece of text.
A definition would typically be rendered in italics or <dfn...</dfn> >
tags and will often be used as a link target for subsequent instances of the
term (or any of its specified synonyms) within a hypertext.
Pod provides formatting codes for specifying inline examples of input, output, code, and metasyntax:
T<> formatting code specifies that the contained text is
terminal output; that is: something that a program might print out.
Such content would typically be rendered in a fixed-width font or with
<samp...</samp> > tags. The contents of a T<> code are always
space-preserved (as if they had an implicit
S<...> around them). The T<> code is the inline equivalent of the
=output block.
K<> formatting code specifies that the contained text is
keyboard input; that is: something that a user might type in. Such
content would typically be rendered in a fixed-width font (preferably a
different font from that used for the T<> formatting code) or with
<kbd...</kbd> > tags. The contents of a K<> code are always
space-preserved. The K<> code is the
inline equivalent of the =input block.
The C<> formatting code specifies that the contained text is code;
that is, something that might appear in a program or specification. Such
content would typically be rendered in a fixed-width font (preferably
a different font from that used for the T<> or K<> formatting
codes) or with <code...</code> > tags. The contents of a C<> code
are space-preserved and verbatim.
The C<> code is the inline equivalent of the =code block.
To include other formatting codes in a C<> code, you can lexically
reconfigure it:
=begin para
=config C<> :allow<E I>
Perl 6 makes extensive use of the C<B<E<laquo>>> and C<B<E<raquo>>>
characters, for example, in a hash look-up:
C<%hashB<I<E<laquo>>>keyB<I<E<raquo>>>>
=end para
C<...> put a =config C<> :allow<E>
at the top of the document
R<> formatting code specifies that the contained text is a
replaceable item, a placeholder, or a metasyntactic variable. It is
used to indicate a component of a syntax or specification that should
eventually be replaced by an actual value. For example:
The basic C<ln> command is: C<ln> R<source_file> R<target_file>
Then enter your details at the prompt:
=for input
Name: R<your surname>
ID: R<your employee number>
Pass: R<your 36-letter password>
<var...</var> > tags. The font used should be the same as that used for
the C<> code, unless the R<> is inside a K<> or T<> code (or
the equivalent =input or =output blocks), in which case their
respective fonts should be used.
The V<> formatting code treats its entire contents as being verbatim,
disregarding every apparent formatting code within it. For example:
The B<V< V<> >> formatting code disarms other codes
such as V< I<>, C<>, B<>, and M<> >.
Note, however that the V<> code only changes the way its
contents are parsed, not the way they are rendered. That is, the
contents are still wrapped and formatted like plain text, and the
effects of any formatting codes surrounding the V<> code
are still applied to its contents. For example the previous example
is rendered:
The
formatting code disarms other codes such as,., , and
You can prespecify formatting codes that remain active within
a V<> code, using the :allow
option.
The Z<> formatting code indicates that its contents constitute a
zero-width comment, which should not be rendered by any renderer.
For example:
The "exeunt" command Z<Think about renaming this command?> is used
to quit all applications.
In Perl 5 POD, the Z<> code was widely used to break up text that would
otherwise be considered mark-up:
In Perl 5 POD, the ZZ<><> code was widely used to break up text
that would otherwise be considered mark-up.
That technique still works, but it's now easier to accomplish the same goal using a verbatim formatting code:
In Perl 5 POD, the B«V<V<Z<>>>» code was widely used to break up text
that would otherwise be considered mark-up.
Moreover, the C<> code automatically treats its contents as being
verbatim, which often eliminates the need for the V<> as well:
In Perl 5 POD, the B«V<C<Z<>>>» code was widely used to break up text
that would otherwise be considered mark-up.
The Z<> formatting code is the inline equivalent of a
=comment block.
Most Pod renderers will provide a mechanism that allows particular Pod
blocks to be explicitly excluded or included if they match a particular
pattern. For example, a renderer might be instructed to omit any block
that contains the pattern /CONFIDENTIAL/. Corresponding "invisibility
markers" can then be placed inside Z<> comments within any block that
should not normally be displayed. For example:
class Widget is Bauble
{
has $.things; #= a collection of other stuff
#={ Z<CONFIDENTIAL>
This variable needs to be replaced for political reasons
}
}
The L<> code is used to specify all kinds of links, filenames, citations,
and cross-references (both internal and external).
A link specification consists of a scheme specifier terminated by a colon, followed by an external address (in the scheme's preferred syntax), followed by an internal address (again, in the scheme's syntax). All three components are optional, though at least one must be present in any link specification.
Usually, in schemes where an internal address makes sense, it will be
separated from the preceding external address by a #, unless the
particular addressing scheme requires some other syntax. When new
addressing schemes are created specifically for Pod it is strongly
recommended that # be used to mark the start of internal addresses.
Standard schemes include:
http: and https: This module needs the LAME library
(available from L<B<http://www.mp3dev.org/mp3/>>)
// it is treated as being relative to
the location of the current document:
See also: L<B<http:tutorial/faq.html>> and
L<B<http:../examples/index.html>>
file: Next, edit the global config file (that is, either
L<B<file:/usr/local/lib/.configrc>> or L<B<file:~/.configrc>>).
/ or a ~ are relative
to the current document's location:
Then, edit the local config file (that is, either
L<B<file:.configrc>> or L<B<file:CONFIG/.configrc>>.
mailto: Please forward bug reports to L<B<mailto:devnull@rt.cpan.org>>
man: This module implements the standard
Unix L<B<man:find(1)>> facilities.
doc:perl --doc.
For example:
You may wish to use L<B<doc:Data::Dumper>> to
view the results. See also: L<B<doc:perldata>>.
defn: He was highly prone to D<lexiphania>: an unfortunate proclivity
for employing grandiloquisms (for example, words such as "proclivity",
"grandiloquism", and indeed "lexiphania").
=defn glossoligation
Restraint of the tongue (voluntary or otherwise)
To treat his chronic L<B<defn:lexiphania>> the doctor prescribed an
immediate L<B<defn:glossoligation>> or, if that proved ineffective,
a complete cephalectomy.
isbn: and issn: The Perl Journal was a registered
serial publication (L<B<issn:1087-903X>>)
To refer to a specific section within a webpage, manpage, or Pod
document, add the name of that section after the main link, separated by
a #. For example:
Also see: L<man:bash(1)B<#Compound Commands>>,
L<doc:perlsynB<#For Loops>>, and
L<http://dev.perl.org/perl6/syn/S04.htmlB<#The_for_statement>>
To refer to a section of the current document, omit the external address:
This mechanism is described under L<doc:B<#Special Features>> below.
The scheme name may also be omitted in that case:
This mechanism is described under L<B<#Special Features>> below.
Normally a link is presented as some rendered version of the link specification itself. However, you can specify an alternate presentation by prefixing the link with the desired text and a vertical bar. Whitespace is not significant on either side of the bar. For example:
This module needs the L<B<LAME library|>http://www.mp3dev.org/mp3/>.
You could also write the code
L<B<in Latin |> doc:Lingua::Romana::Perligata>
His L<B<lexiphanic|>defn:lexiphania>> tendencies were, alas, incurable.
A second kind of link—the P<> or placement link—works
in the opposite direction. Instead of directing focus out to another
document, it allows you to assimilate the contents of another document
into your own.
In other words, the P<> formatting code takes a URI and (where possible)
inserts the contents of the corresponding document inline in place of the
code itself.
P<> codes are handy for breaking out standard elements of
your documentation set into reusable components that can then be
incorporated directly into multiple documents. For example:
=COPYRIGHT
P<file:/shared/docs/std_copyright.pod>
=DISCLAIMER
P<http://www.MegaGigaTeraPetaCorp.com/std/disclaimer.txt>
might produce:
Copyright
This document is copyright (c) MegaGigaTeraPetaCorp, 2006. All rights reserved.
Disclaimer
ABSOLUTELY NO WARRANTY IS IMPLIED. NOT EVEN OF ANY KIND. WE HAVE SOLD YOU THIS SOFTWARE WITH NO HINT OF A SUGGESTION THAT IT IS EITHER USEFUL OR USABLE. AS FOR GUARANTEES OF CORRECTNESS...DON'T MAKE US LAUGH! AT SOME TIME IN THE FUTURE WE MIGHT DEIGN TO SELL YOU UPGRADES THAT PURPORT TO ADDRESS SOME OF THE APPLICATION'S MANY DEFICIENCIES, BUT NO PROMISES THERE EITHER. WE HAVE MORE LAWYERS ON STAFF THAN YOU HAVE TOTAL EMPLOYEES, SO DON'T EVEN *THINK* ABOUT SUING US. HAVE A NICE DAY.
If a renderer cannot find or access the external data source for a placement link, it must issue a warning and render the URI directly in some form, possibly as an outwards link. For example:
Copyright
See: std_copyright.pod
Disclaimer
You can use any of the following URI forms (see #Links) in a placement link:
http: and https:
file:
man:
doc:
toc:
The toc: form is a special pseudo-scheme that inserts a table of contents
in place of the P<> code. After the colon, list the block types that you
wish to include in the table of contents. For example, to place a table of
contents listing only top- and second-level headings:
P<toc: head1 head2>
To place a table of contents that lists the top four levels of headings, as well as any tables:
P<toc: head1 head2 head3 head4 table>
To place a table of diagrams (assuming a user-defined Diagram block):
P<toc: Diagram>
Note also that, for P<toc:...>, all semantic blocks are treated as equivalent to head1 headings, and the
=item1/=item equivalence is preserved.
A document may have as many P<toc:...> placements as necessary.
A variation on placement codes is the A<> code, which is replaced
by the contents of the named alias or object specified within its delimiters.
For example:
=alias PROGNAME Earl Irradiatem Eventually
=alias VENDOR 4D Kingdoms
=alias TERMS_URL L<http://www.4dk.com/eie>
The use of A<PROGNAME> is subject to the terms and conditions
laid out by A<VENDOR>, as specified at A<TERMS_URL>.
Any compile-time Perl 6 object that starts with a sigil is automatically
available within an alias placement as well. Unless the object is already
a string type, it is converted to a string during document-generation by
implicitly calling .perl on it.
So, for example, a document can refer to its own filename (as
A<$?FILE>), or to the subroutine inside which the specific Pod is nested
(as A<$?ROUTINE>), or to the current class (as A<$?CLASS>).
Similarly, the value of any program constants defined with sigils can be
easily reproduced in documentation:
# Actual code...
constant $GROWTH_RATE of Num where 0..* = 1.6;
=pod
=head4 Standard Growth Rate
The standard growth rate is assumed to be A<$GROWTH_RATE>.
Non-mutating method calls on these objects are also allowed, so a
document can reproduce the surrounding subroutine's signature
(A<$?ROUTINE.signature>) or the type of a constant
(A<$GROWTH_RATE.WHAT>).
See #Aliases for further details of the aliasing macro mechanism.
Any text enclosed in an S<> code is formatted normally, except that
every whitespace character in it—including any newline—is
preserved. These characters are also treated as being non-breaking
(except for the newlines, of course). For example:
The emergency signal is: S<
dot dot dot dash dash dash dot dot dot>.
would be formatted like so:
The emergency signal is:
dot dot dot dash dash dash dot dot dot.
rather than:
The emergency signal is: dot dot dot dash dash dash dot dot dot.
To include Unicode code points or HTML5 character references in a
Pod document, specify the required entity using the E<> code.
If the E<> contains a number, that number is treated as the decimal
Unicode value for the desired code point. For example:
Perl 6 makes considerable use of E<171> and E<187>.
You can also use explicit binary, octal, decimal, or hexadecimal numbers (using the Perl 6 notations for explicitly based numbers):
Perl 6 makes considerable use of E<0b10101011> and E<0b10111011>.
Perl 6 makes considerable use of E<0o253> and E<0o273>.
Perl 6 makes considerable use of E<0d171> and E<0d187>.
Perl 6 makes considerable use of E<0xAB> and E<0xBB>.
If the E<> contains anything that is not a number, the contents are
interpreted as a Unicode character name (which is always uppercase), or
else as an HTML5 named character reference. For example:
Perl 6 makes considerable use of E<LEFT DOUBLE ANGLE BRACKET>
and E<RIGHT DOUBLE ANGLE BRACKET>.
or, equivalently:
Perl 6 makes considerable use of E<laquo> and E<raquo>.
Multiple consecutive entities (in any format) can be specified in a
single E<> code, separated by semicolons:
Perl 6 makes considerable use of E<LEFT DOUBLE ANGLE BRACKET;hellip;0xBB>.
Anything enclosed in an X<> code is an index entry. The contents
of the code are both formatted into the document and used as the
(case-insensitive) index entry:
An X<array> is an ordered list of scalars indexed by number,
starting with 0. A X<hash> is an unordered collection of scalar
values indexed by their associated string key.
You can specify an index entry in which the indexed text and the index entry are different, by separating the two with a vertical bar:
An X<array|arrays> is an ordered list of scalars indexed by number,
starting with 0. A X<hash|hashes> is an unordered collection of
scalar values indexed by their associated string key.
In the two-part form, the index entry comes after the bar and is case-sensitive.
You can specify hierarchical index entries by separating indexing levels with commas:
An X<array|B<arrays, definition of>> is an ordered list of scalars
indexed by number, starting with 0. A X<hash|B<hashes, definition of>>
is an unordered collection of scalar values indexed by their
associated string key.
You can specify two or more entries for a single indexed text, by separating the entries with semicolons:
A X<hash|B<hashes, definition of; associative arrays>>
is an unordered collection of scalar values indexed by their
associated string key.
The indexed text can be empty, creating a "zero-width" index entry:
X<|puns, deliberate>This is called the "Orcish Manoeuvre"
because you "OR" the "cache".
Anything enclosed in an N<> code is an inline note.
For example:
Use a C<for> loop instead.N<The Perl 6 C<for> loop is far more
powerful than its Perl 5 predecessor.> Preferably with an explicit
iterator variable.
Renderers may render such annotations in a variety of ways: as footnotes, as endnotes, as sidebars, as pop-ups, as tooltips, as expandable tags, etc. They are never, however, rendered as unmarked inline text. So the previous example might be rendered as:
Use a
forloop instead.† Preferably with an explicit iterator variable.
and later:
Footnotes
† The Perl 6
forloop is far more powerful than its Perl 5 predecessor.
Modules loaded with a DOC use
can define classes that implement new formatting codes, which can
then be specified using the M<> code. An M<> code must start with
a colon-terminated scheme specifier. The rest of the enclosed text is
treated as the (verbatim) contents of the formatting code. For example:
DOC use Pod6::TT;
=head1 Overview of the M<TT: $CLASSNAME > class
(version M<TT: $VERSION>)
M<TT: get_description($CLASSNAME) >
The M<> formatting code is the inline equivalent of a
named block.
Internally an M<> code is converted to an object derived from the
Pod6::FormattingCode::Named class. The name of the scheme becomes
the final component of the object's classname. For instance, the M<>
code in the previous example would be converted to a
Pod6::FormattingCode::Named::TT object, whose .typename
method retrieves the string "TT" and whose .contents
method retrieves a list of the formatting code's (verbatim,
unformatted) contents.
If the formatting code is unrecognized, the contents of the code (i.e. everything after the first colon) would normally be rendered as ordinary text.
By default, Pod assumes that documents are Unicode, encoded in one of the three common schemes (UTF-8, UTF-16, or UTF-32). The particular scheme a document uses is autodiscovered by examination of the first few bytes of the file (where possible). If the autodiscovery fails, UTF-8 is assumed, and parsers may treat any non-UTF-8 bytes later in the document as fatal errors.
At any point in a document, you can explicitly set or change the encoding
of its content using the =encoding directive:
=encoding ShiftJIS
=encoding Macintosh
=encoding KOI8-R
The specified encoding is used from the start of the next line in
the document. If a second =encoding directive is encountered, the
current encoding changes again after that line. Note, however, that
the second encoding directive must itself be encoded using the first
encoding scheme.
This requirement also applies to an =encoding directive at the very
beginning of the file. That is, it must itself be encoded in
the default UTF-8, -16, or -32. However, as a special case, the
autodiscovery mechanism will (as far as possible) also attempt to
recognize "self-encoded" =encoding directives that begin at the first
byte of the file. For example, at the start of a ShiftJIS-encoded file
you can specify =encoding ShiftJIS in the ShiftJIS encoding.
An =encoding directive affects any ambient code between the Pod
as well. That is, Perl 6 uses =encoding directives to determine the
encoding of its source code as well as that of any documentation.
Note that =encoding is a fundamental Pod directive, like =begin or
=for; it is not an instance of an abbreviated block. Hence there is no paragraph or delimited form of the =encoding
directive (just as there is no paragraph or delimited form of =begin).
The =config directive allows you to prespecify standard configuration
information that is applied to every block of a particular type.
For example, to specify particular formatting for different levels of heading, you could preconfigure all the heading blocks with appropriate formatting schemes:
=config head1 :formatted<B U> :numbered
=config head2 :like<head1> :formatted<I>
=config head3 :formatted<U>
=config head4 :like<head3> :formatted<I>
The general syntax for configuration directives is:
=config BLOCK_TYPE CONFIG OPTIONS
= OPTIONAL EXTRA CONFIG OPTIONS
Like =encoding, a =config is a directive, not a block. Hence,
there is no paragraph or delimited form of the =config directive.
Each =config specification is lexically scoped to the surrounding
block in which it is specified.
Note that, if a particular block later explicitly specifies a configuration option with the same key, that option overrides the pre-configured option. For example, given the heading configurations in the previous example, to specify a non-basic second-level heading:
=for head2 :formatted<I U>
Details
The :like option causes the current formatting options for the
named block type to be (lexically) replaced by the complete
formatting information of the block type specified as the :like's
value. That other block type must already have been preconfigured. Any
additional formatting specifications are subsequently added to that
config. For example:
=comment In the current scope make =head2 an "important" variant of =head1
=config head2 :like<head1> :formatted<I>
Incidentally, this also means you can arrange for an explicit :formatted
option to augment an existing =config, rather than replacing
it. Like so:
=comment Mark this =head3 (but only this one) as being important
(in addition to the normal formatting)...
=head3 :like<head3> :formatted<I>
You can also lexically preconfigure a formatting code, by naming it with a pair of angles as a suffix. For example:
=comment Always allow E<> codes in any (implicit or explicit) V<> code...
=config V<> :allow<E>
=comment All inline code to be marked as important...
=config C<> :formatted<I>
Note that, even though the formatting code is named using single-angles, the preconfiguration applies regardless of the actual delimiters used on subsequent instances of the code.
The =alias directive provides a way to define lexically scoped
synonyms for longer Pod sequences, (meta)object declarators from the
code, or even entire chunks of ambient source. These synonyms can then
be inserted into subsequent Pod using the
A<> formatting code.
Note that =alias is a fundamental Pod directive, like =begin or
=for; there are no equivalent paragraph or delimited forms.
There are two forms of =alias directive: macro aliases and contextual
aliases. Both forms are lexically scoped to the surrounding Pod block.
The simplest form of alias takes two arguments. The first is an identifier (which is usually specified in uppercase, though this is certainly not mandatory). The second argument consists of one or more lines of replacement text.
This creates a lexically scoped Perl 6 macro that can be invoked during
document generation by placing the identifier (i.e. the first argument
of the alias) in an A<> formatting code. This formatting code is then
replaced by the text returned by new macro.
The replacement text returned by the alias macro begins at the first
non-whitespace character after the alias's identifier, and continues to
the end of the line. You can extend the replacement text over multiple
lines by starting the following line(s) with an = (at the same level
of indentation as the =alias directive itself) followed by at least
one whitespace. Each addition line of replacement text uses the original
line's (virtual) left margin, as specified by the indentation of the
replacement text on the =alias line.
For example:
=alias PROGNAME Earl Irradiatem Evermore
=alias VENDOR 4D Kingdoms
=alias TERMS_URLS =item L<http://www.4dk.com/eie>
= =item L<http://www.4dk.co.uk/eie.io/>
= =item L<http://www.fordecay.ch/canttouchthis>
The use of A<PROGNAME> is subject to the terms and conditions
laid out by A<VENDOR>, as specified at:
A<TERMS_URL>
would produce:
The use of Earl Irradiatem Evermore is subject to the terms and conditions laid out by 4D Kingdoms Inc, as specified at:
=item http://www.4dk.com/eie =item http://www.4dk.co.uk/eie.io/ =item http://www.fordecay.ch/canttouchthis
The advantage of using aliases is, obviously, that the same alias can be reused in multiple places in the documentation. Then, if the replacement text ever has to be changed, it need only be modified in a single place:
=alias PROGNAME Count Krunchem Constantly
=alias VENDOR Last Chance Receivers Intl
=alias TERMS_URLS L<http://www.c11.com/generic_conditions>
If the =alias directive is specified with only a single argument
(that is, with only its identifier), a contextual alias is created. In
this form, the =alias directive must be followed immediately (on the
next non-blank line) by ambient code.
The single argument is then used as the name of the alias being created, and some portion of the following code is used as the value returned by the alias macro.
Note that the code block following the =alias line is still treated
as real code by the Perl 6 parser, but its contents are also used to
create the replacement macro of the alias. This allows the developer to
reproduce chunks of actual source code directly in the documentation,
without having to copy it.
If the code following the one-argument =alias directive begins with a
sequence of one or more repetitions of any opening bracket character,
the replacement macro returns a string containing everything from the
end of that opening sequence to just before the corresponding closing
bracket sequence. For example:
# This is actual code...
sub hash_function ($key)
=alias HASHCODE
{
my $hash = 0;
for $key.split("") -> $char {
$hash = $hash*33 + $char.ord;
}
return $hash;
}
=begin pod
An ancient (but fast) hashing algorithm is used:
=begin code :allow<A>
A<HASHCODE>
=end code
=end pod
This would produce:
An ancient (but fast) hashing algorithm is used:
my $hash = 0; for $key.split("") -> $char { $hash *= 33; $hash += $char.ord; } return $hash;
Alternatively, if the =alias directive is not followed by an
opening bracket, it must be followed by a declarator (such as my,
class, sub, etc.) The declared object then becomes the (read-only)
return value of the alias. For example:
=alias CLASSNAME
class Database::Handle {
=alias ATTR
has IO $!handle;
=alias OPEN
my Bool method open ($filename?) {...}
=alias DEFNAME
constant Str DEFAULT_FILENAME = 'db.log';
=for para
Note that the A<OPEN.name> method of class A<CLASSNAME>
stores the resulting low-level database handle
in its private A<ATTR.name> attribute. By default,
handles are opened to the file "A<DEFNAME>".
}
This would produce:
Note that the
openmethod of classDatabase::Handlestores the resulting low-level database handle in its private$!handleattribute. By default, handles are opened to the file "db.log".
Pod is just a collection of specialized forms of Perl 6 comment. Every Perl 6 implementation must provide a special command-line flag that locates, parses, and processes Pod to produce documentation. That flag is --doc.
Hence, to read Pod documentation you would type things like:
perl --doc perlrun
perl --doc DBI::DBD::Metadata
perl --doc ./lib/My/Module.pm
When the Perl 6 interpreter is run in this mode, it sets the compiler
hint $?DOC to true. If the --doc flag is given a value, that value
(with a but true added) is placed in $?DOC. This can be used to
specify, for example, the output format desired:
perl --doc=html perldelta > perldelta.html
Under --doc, the interpreter runs in a special mode, parsing the
source code (including the Pod, as it always does) during compilation
and building the program's syntax tree. However, during parsing and
initialization under --doc, the interpreter executes any
BEGIN, CHECK, and INIT blocks (and equivalents, such as use
statements and subroutine declarations) that are preceded by the special
prefix: DOC
When the --doc is not specified on the commandline, blocks and
statements that are preceded by the DOC prefix are not executed at all.
By default, once the DOC INIT phase is complete, the interpreter then
calls a special default DOC INIT block that walks the AST and
generates the documentation, guided by the content of the $?DOC hint,
the $=POD tree, and any DOC blocks that have loaded Pod-related
handler code.
Because the conversion of documentation is just a variation on the
standard Perl 6 compilation process, the processing of any given file of
Pod can be modified from within that file itself by the appropriate
insertion of DOC blocks. For example:
DOC use Pod6::Markovian;
or:
DOC BEGIN {
use Pod6::Literate;
if ($?DOC ~~ /short/) {
literate_sequence(<
NAME
AUTHOR
SYNOPSIS
COPYRIGHT
WARRANTY
DESCRIPTION
INTERFACE
DIAGNOSTICS
>);
}
else {
literate_sequence(:default);
}
You can even replace the standard Pod processor with your own, so
long as you remember to exit before the default DOC INIT can run:
DOC INIT {
use My::Pod::To::Text;
pod_to_text( $=POD );
exit(0);
}
The idea is that developers will be able to add their own documentation
mechanisms simply by loading a module (via a DOC use) to augment or
override the default documentation behaviour. Such mechanisms can then
be built using code written in standard Perl 6 that accesses $=POD,
as well as using the .WHY and .WHEREFORE introspection methods of
any constructs that have attached Pod blocks.
Note also that this mechanism means that, on many systems, you can create a self-converting documentation file like so:
#! /usr/bin/perl6 --doc
=begin pod
=head1 A document that can write itself
Executing this document from the commandline will automatically
convert it to a readable text representation.
=head2 Et cetera
...
=end pod
Directive Specifies _________ ____________________________________________________ =beginStart of an explicitly terminated block =configLexical modifications to a block or formatting code =encodingEncoding scheme for subsequent text =endExplicit termination of a =beginblock=forStart of an implicitly (blank-line) terminated block =aliasDefine a Pod macro
Block typename Specifies ______________ ___________________________________________________ =codeVerbatim pre-formatted sample source code =commentContent to be ignored by all renderers =defnDefinition of a term =headNNth-level heading =inputPre-formatted sample input =itemFirst-level list item =itemNNth-level list item =nestedNest block contents within the current context =outputPre-formatted sample output =paraOrdinary paragraph =podNo "ambient" blocks inside =tableSimple rectangular table =DATAPerl 6 data section =ENDNo ambient blocks after this point =RESERVEDSemantic blocks ( =SYNOPIS,=BUGS, etc.)=TypenameUser-defined block
Formatting code _______________ A<...>B<...>C<...>D<...>Specifies ___________________________________________________ Replaced by contents of specified macro/object Basis/focus of sentence (typically rendered bold) Code (typically rendered fixed-width) ...;...>> Definition ( D<R<defined term>>synonym;synonym;...>>) E<...;...>I<...>K<...>L<...>Entity names or numeric codepoints ( E<R<entity1>;R<entity2>;...>) Important (typically rendered in italics) Keyboard input (typically rendered fixed-width) ...>>Link ( L<R<display text>>destination URI>>) M<...:...>N<...>P<...>>R<...S<...>T<...>U<...>>V<...X<...>Module-defined code ( M<R<scheme>:R<contents>>) Note (not rendered inline) Placement link Replaceable component or metasyntax Space characters to be preserved Terminal output (typically rendered fixed-width) Unusual (typically rendered with underlining) Verbatim (internal formatting codes ignored) ..,..;...>>Index entry ( X<R<display text>>entry,subentry;...>>)
NOTES
1. as specified in Synopsis 2