1 #############################################################################
2 # Pod/Parser.pm -- package which defines a base class for parsing POD docs.
4 # Copyright (C) 1996-2000 by Bradford Appleton. All rights reserved.
5 # This file is part of "PodParser". PodParser is free software;
6 # you can redistribute it and/or modify it under the same terms
8 #############################################################################
12 use vars qw($VERSION);
13 $VERSION = 1.14; ## Current version of this package
14 require 5.005; ## requires this Perl version or later
16 #############################################################################
20 Pod::Parser - base class for creating POD filters and translators
27 @ISA = qw(Pod::Parser);
30 my ($parser, $command, $paragraph, $line_num) = @_;
31 ## Interpret the command and its text; sample actions might be:
32 if ($command eq 'head1') { ... }
33 elsif ($command eq 'head2') { ... }
34 ## ... other commands and their actions
35 my $out_fh = $parser->output_handle();
36 my $expansion = $parser->interpolate($paragraph, $line_num);
37 print $out_fh $expansion;
41 my ($parser, $paragraph, $line_num) = @_;
42 ## Format verbatim paragraph; sample actions might be:
43 my $out_fh = $parser->output_handle();
44 print $out_fh $paragraph;
48 my ($parser, $paragraph, $line_num) = @_;
49 ## Translate/Format this block of text; sample actions might be:
50 my $out_fh = $parser->output_handle();
51 my $expansion = $parser->interpolate($paragraph, $line_num);
52 print $out_fh $expansion;
55 sub interior_sequence {
56 my ($parser, $seq_command, $seq_argument) = @_;
57 ## Expand an interior sequence; sample actions might be:
58 return "*$seq_argument*" if ($seq_command eq 'B');
59 return "`$seq_argument'" if ($seq_command eq 'C');
60 return "_${seq_argument}_'" if ($seq_command eq 'I');
61 ## ... other sequence commands and their resulting text
66 ## Create a parser object and have it parse file whose name was
67 ## given on the command-line (use STDIN if no files were given).
68 $parser = new MyParser();
69 $parser->parse_from_filehandle(\*STDIN) if (@ARGV == 0);
70 for (@ARGV) { $parser->parse_from_file($_); }
74 perl5.005, Pod::InputObjects, Exporter, Symbol, Carp
82 B<Pod::Parser> is a base class for creating POD filters and translators.
83 It handles most of the effort involved with parsing the POD sections
84 from an input stream, leaving subclasses free to be concerned only with
85 performing the actual translation of text.
87 B<Pod::Parser> parses PODs, and makes method calls to handle the various
88 components of the POD. Subclasses of B<Pod::Parser> override these methods
89 to translate the POD into whatever output format they desire.
93 To create a POD filter for translating POD documentation into some other
94 format, you create a subclass of B<Pod::Parser> which typically overrides
95 just the base class implementation for the following methods:
113 B<interior_sequence()>
117 You may also want to override the B<begin_input()> and B<end_input()>
118 methods for your subclass (to perform any needed per-file and/or
119 per-document initialization or cleanup).
121 If you need to perform any preprocesssing of input before it is parsed
122 you may want to override one or more of B<preprocess_line()> and/or
123 B<preprocess_paragraph()>.
125 Sometimes it may be necessary to make more than one pass over the input
126 files. If this is the case you have several options. You can make the
127 first pass using B<Pod::Parser> and override your methods to store the
128 intermediate results in memory somewhere for the B<end_pod()> method to
129 process. You could use B<Pod::Parser> for several passes with an
130 appropriate state variable to control the operation for each pass. If
131 your input source can't be reset to start at the beginning, you can
132 store it in some other structure as a string or an array and have that
133 structure implement a B<getline()> method (which is all that
134 B<parse_from_filehandle()> uses to read input).
136 Feel free to add any member data fields you need to keep track of things
137 like current font, indentation, horizontal or vertical position, or
138 whatever else you like. Be sure to read L<"PRIVATE METHODS AND DATA">
139 to avoid name collisions.
141 For the most part, the B<Pod::Parser> base class should be able to
142 do most of the input parsing for you and leave you free to worry about
143 how to intepret the commands and translate the result.
145 Note that all we have described here in this quick overview is the
146 simplest most straightforward use of B<Pod::Parser> to do stream-based
147 parsing. It is also possible to use the B<Pod::Parser::parse_text> function
148 to do more sophisticated tree-based parsing. See L<"TREE-BASED PARSING">.
150 =head1 PARSING OPTIONS
152 A I<parse-option> is simply a named option of B<Pod::Parser> with a
153 value that corresponds to a certain specified behavior. These various
154 behaviors of B<Pod::Parser> may be enabled/disabled by setting
155 or unsetting one or more I<parse-options> using the B<parseopts()> method.
156 The set of currently accepted parse-options is as follows:
160 =item B<-want_nonPODs> (default: unset)
162 Normally (by default) B<Pod::Parser> will only provide access to
163 the POD sections of the input. Input paragraphs that are not part
164 of the POD-format documentation are not made available to the caller
165 (not even using B<preprocess_paragraph()>). Setting this option to a
166 non-empty, non-zero value will allow B<preprocess_paragraph()> to see
167 non-POD sections of the input as well as POD sections. The B<cutting()>
168 method can be used to determine if the corresponding paragraph is a POD
169 paragraph, or some other input paragraph.
171 =item B<-process_cut_cmd> (default: unset)
173 Normally (by default) B<Pod::Parser> handles the C<=cut> POD directive
174 by itself and does not pass it on to the caller for processing. Setting
175 this option to a non-empty, non-zero value will cause B<Pod::Parser> to
176 pass the C<=cut> directive to the caller just like any other POD command
177 (and hence it may be processed by the B<command()> method).
179 B<Pod::Parser> will still interpret the C<=cut> directive to mean that
180 "cutting mode" has been (re)entered, but the caller will get a chance
181 to capture the actual C<=cut> paragraph itself for whatever purpose
184 =item B<-warnings> (default: unset)
186 Normally (by default) B<Pod::Parser> recognizes a bare minimum of
187 pod syntax errors and warnings and issues diagnostic messages
188 for errors, but not for warnings. (Use B<Pod::Checker> to do more
189 thorough checking of POD syntax.) Setting this option to a non-empty,
190 non-zero value will cause B<Pod::Parser> to issue diagnostics for
191 the few warnings it recognizes as well as the errors.
195 Please see L<"parseopts()"> for a complete description of the interface
196 for the setting and unsetting of parse-options.
200 #############################################################################
205 use Pod::InputObjects;
216 ## These "variables" are used as local "glob aliases" for performance
217 use vars qw(%myData %myOpts @input_stack);
219 #############################################################################
221 =head1 RECOMMENDED SUBROUTINE/METHOD OVERRIDES
223 B<Pod::Parser> provides several methods which most subclasses will probably
224 want to override. These methods are as follows:
228 ##---------------------------------------------------------------------------
232 $parser->command($cmd,$text,$line_num,$pod_para);
234 This method should be overridden by subclasses to take the appropriate
235 action when a POD command paragraph (denoted by a line beginning with
236 "=") is encountered. When such a POD directive is seen in the input,
237 this method is called and is passed:
243 the name of the command for this POD paragraph
247 the paragraph text for the given POD paragraph command.
251 the line-number of the beginning of the paragraph
255 a reference to a C<Pod::Paragraph> object which contains further
256 information about the paragraph command (see L<Pod::InputObjects>
261 B<Note> that this method I<is> called for C<=pod> paragraphs.
263 The base class implementation of this method simply treats the raw POD
264 command as normal block of paragraph text (invoking the B<textblock()>
265 method with the command paragraph).
270 my ($self, $cmd, $text, $line_num, $pod_para) = @_;
271 ## Just treat this like a textblock
272 $self->textblock($pod_para->raw_text(), $line_num, $pod_para);
275 ##---------------------------------------------------------------------------
279 $parser->verbatim($text,$line_num,$pod_para);
281 This method may be overridden by subclasses to take the appropriate
282 action when a block of verbatim text is encountered. It is passed the
283 following parameters:
289 the block of text for the verbatim paragraph
293 the line-number of the beginning of the paragraph
297 a reference to a C<Pod::Paragraph> object which contains further
298 information about the paragraph (see L<Pod::InputObjects>
303 The base class implementation of this method simply prints the textblock
304 (unmodified) to the output filehandle.
309 my ($self, $text, $line_num, $pod_para) = @_;
310 my $out_fh = $self->{_OUTPUT};
314 ##---------------------------------------------------------------------------
316 =head1 B<textblock()>
318 $parser->textblock($text,$line_num,$pod_para);
320 This method may be overridden by subclasses to take the appropriate
321 action when a normal block of POD text is encountered (although the base
322 class method will usually do what you want). It is passed the following
329 the block of text for the a POD paragraph
333 the line-number of the beginning of the paragraph
337 a reference to a C<Pod::Paragraph> object which contains further
338 information about the paragraph (see L<Pod::InputObjects>
343 In order to process interior sequences, subclasses implementations of
344 this method will probably want to invoke either B<interpolate()> or
345 B<parse_text()>, passing it the text block C<$text>, and the corresponding
346 line number in C<$line_num>, and then perform any desired processing upon
349 The base class implementation of this method simply prints the text block
350 as it occurred in the input stream).
355 my ($self, $text, $line_num, $pod_para) = @_;
356 my $out_fh = $self->{_OUTPUT};
357 print $out_fh $self->interpolate($text, $line_num);
360 ##---------------------------------------------------------------------------
362 =head1 B<interior_sequence()>
364 $parser->interior_sequence($seq_cmd,$seq_arg,$pod_seq);
366 This method should be overridden by subclasses to take the appropriate
367 action when an interior sequence is encountered. An interior sequence is
368 an embedded command within a block of text which appears as a command
369 name (usually a single uppercase character) followed immediately by a
370 string of text which is enclosed in angle brackets. This method is
371 passed the sequence command C<$seq_cmd> and the corresponding text
372 C<$seq_arg>. It is invoked by the B<interpolate()> method for each interior
373 sequence that occurs in the string that it is passed. It should return
374 the desired text string to be used in place of the interior sequence.
375 The C<$pod_seq> argument is a reference to a C<Pod::InteriorSequence>
376 object which contains further information about the interior sequence.
377 Please see L<Pod::InputObjects> for details if you need to access this
378 additional information.
380 Subclass implementations of this method may wish to invoke the
381 B<nested()> method of C<$pod_seq> to see if it is nested inside
382 some other interior-sequence (and if so, which kind).
384 The base class implementation of the B<interior_sequence()> method
385 simply returns the raw text of the interior sequence (as it occurred
386 in the input) to the caller.
390 sub interior_sequence {
391 my ($self, $seq_cmd, $seq_arg, $pod_seq) = @_;
392 ## Just return the raw text of the interior sequence
393 return $pod_seq->raw_text();
396 #############################################################################
398 =head1 OPTIONAL SUBROUTINE/METHOD OVERRIDES
400 B<Pod::Parser> provides several methods which subclasses may want to override
401 to perform any special pre/post-processing. These methods do I<not> have to
402 be overridden, but it may be useful for subclasses to take advantage of them.
406 ##---------------------------------------------------------------------------
410 my $parser = Pod::Parser->new();
412 This is the constructor for B<Pod::Parser> and its subclasses. You
413 I<do not> need to override this method! It is capable of constructing
414 subclass objects as well as base class objects, provided you use
415 any of the following constructor invocation styles:
417 my $parser1 = MyParser->new();
418 my $parser2 = new MyParser();
419 my $parser3 = $parser2->new();
421 where C<MyParser> is some subclass of B<Pod::Parser>.
423 Using the syntax C<MyParser::new()> to invoke the constructor is I<not>
424 recommended, but if you insist on being able to do this, then the
425 subclass I<will> need to override the B<new()> constructor method. If
426 you do override the constructor, you I<must> be sure to invoke the
427 B<initialize()> method of the newly blessed object.
429 Using any of the above invocations, the first argument to the
430 constructor is always the corresponding package name (or object
431 reference). No other arguments are required, but if desired, an
432 associative array (or hash-table) my be passed to the B<new()>
435 my $parser1 = MyParser->new( MYDATA => $value1, MOREDATA => $value2 );
436 my $parser2 = new MyParser( -myflag => 1 );
438 All arguments passed to the B<new()> constructor will be treated as
439 key/value pairs in a hash-table. The newly constructed object will be
440 initialized by copying the contents of the given hash-table (which may
441 have been empty). The B<new()> constructor for this class and all of its
442 subclasses returns a blessed reference to the initialized object (hash-table).
447 ## Determine if we were called via an object-ref or a classname
449 my $class = ref($this) || $this;
450 ## Any remaining arguments are treated as initial values for the
451 ## hash that is used to represent this object.
453 my $self = { %params };
454 ## Bless ourselves into the desired class and perform any initialization
460 ##---------------------------------------------------------------------------
462 =head1 B<initialize()>
464 $parser->initialize();
466 This method performs any necessary object initialization. It takes no
467 arguments (other than the object instance of course, which is typically
468 copied to a local variable named C<$self>). If subclasses override this
469 method then they I<must> be sure to invoke C<$self-E<gt>SUPER::initialize()>.
478 ##---------------------------------------------------------------------------
480 =head1 B<begin_pod()>
482 $parser->begin_pod();
484 This method is invoked at the beginning of processing for each POD
485 document that is encountered in the input. Subclasses should override
486 this method to perform any per-document initialization.
495 ##---------------------------------------------------------------------------
497 =head1 B<begin_input()>
499 $parser->begin_input();
501 This method is invoked by B<parse_from_filehandle()> immediately I<before>
502 processing input from a filehandle. The base class implementation does
503 nothing, however, subclasses may override it to perform any per-file
506 Note that if multiple files are parsed for a single POD document
507 (perhaps the result of some future C<=include> directive) this method
508 is invoked for every file that is parsed. If you wish to perform certain
509 initializations once per document, then you should use B<begin_pod()>.
518 ##---------------------------------------------------------------------------
520 =head1 B<end_input()>
522 $parser->end_input();
524 This method is invoked by B<parse_from_filehandle()> immediately I<after>
525 processing input from a filehandle. The base class implementation does
526 nothing, however, subclasses may override it to perform any per-file
529 Please note that if multiple files are parsed for a single POD document
530 (perhaps the result of some kind of C<=include> directive) this method
531 is invoked for every file that is parsed. If you wish to perform certain
532 cleanup actions once per document, then you should use B<end_pod()>.
541 ##---------------------------------------------------------------------------
547 This method is invoked at the end of processing for each POD document
548 that is encountered in the input. Subclasses should override this method
549 to perform any per-document finalization.
558 ##---------------------------------------------------------------------------
560 =head1 B<preprocess_line()>
562 $textline = $parser->preprocess_line($text, $line_num);
564 This method should be overridden by subclasses that wish to perform
565 any kind of preprocessing for each I<line> of input (I<before> it has
566 been determined whether or not it is part of a POD paragraph). The
567 parameter C<$text> is the input line; and the parameter C<$line_num> is
568 the line number of the corresponding text line.
570 The value returned should correspond to the new text to use in its
571 place. If the empty string or an undefined value is returned then no
572 further processing will be performed for this line.
574 Please note that the B<preprocess_line()> method is invoked I<before>
575 the B<preprocess_paragraph()> method. After all (possibly preprocessed)
576 lines in a paragraph have been assembled together and it has been
577 determined that the paragraph is part of the POD documentation from one
578 of the selected sections, then B<preprocess_paragraph()> is invoked.
580 The base class implementation of this method returns the given text.
584 sub preprocess_line {
585 my ($self, $text, $line_num) = @_;
589 ##---------------------------------------------------------------------------
591 =head1 B<preprocess_paragraph()>
593 $textblock = $parser->preprocess_paragraph($text, $line_num);
595 This method should be overridden by subclasses that wish to perform any
596 kind of preprocessing for each block (paragraph) of POD documentation
597 that appears in the input stream. The parameter C<$text> is the POD
598 paragraph from the input file; and the parameter C<$line_num> is the
599 line number for the beginning of the corresponding paragraph.
601 The value returned should correspond to the new text to use in its
602 place If the empty string is returned or an undefined value is
603 returned, then the given C<$text> is ignored (not processed).
605 This method is invoked after gathering up all the lines in a paragraph
606 and after determining the cutting state of the paragraph,
607 but before trying to further parse or interpret them. After
608 B<preprocess_paragraph()> returns, the current cutting state (which
609 is returned by C<$self-E<gt>cutting()>) is examined. If it evaluates
610 to true then input text (including the given C<$text>) is cut (not
611 processed) until the next POD directive is encountered.
613 Please note that the B<preprocess_line()> method is invoked I<before>
614 the B<preprocess_paragraph()> method. After all (possibly preprocessed)
615 lines in a paragraph have been assembled together and either it has been
616 determined that the paragraph is part of the POD documentation from one
617 of the selected sections or the C<-want_nonPODs> option is true,
618 then B<preprocess_paragraph()> is invoked.
620 The base class implementation of this method returns the given text.
624 sub preprocess_paragraph {
625 my ($self, $text, $line_num) = @_;
629 #############################################################################
631 =head1 METHODS FOR PARSING AND PROCESSING
633 B<Pod::Parser> provides several methods to process input text. These
634 methods typically won't need to be overridden (and in some cases they
635 can't be overridden), but subclasses may want to invoke them to exploit
640 ##---------------------------------------------------------------------------
642 =head1 B<parse_text()>
644 $ptree1 = $parser->parse_text($text, $line_num);
645 $ptree2 = $parser->parse_text({%opts}, $text, $line_num);
646 $ptree3 = $parser->parse_text(\%opts, $text, $line_num);
648 This method is useful if you need to perform your own interpolation
649 of interior sequences and can't rely upon B<interpolate> to expand
650 them in simple bottom-up order.
652 The parameter C<$text> is a string or block of text to be parsed
653 for interior sequences; and the parameter C<$line_num> is the
654 line number curresponding to the beginning of C<$text>.
656 B<parse_text()> will parse the given text into a parse-tree of "nodes."
657 and interior-sequences. Each "node" in the parse tree is either a
658 text-string, or a B<Pod::InteriorSequence>. The result returned is a
659 parse-tree of type B<Pod::ParseTree>. Please see L<Pod::InputObjects>
660 for more information about B<Pod::InteriorSequence> and B<Pod::ParseTree>.
662 If desired, an optional hash-ref may be specified as the first argument
663 to customize certain aspects of the parse-tree that is created and
664 returned. The set of recognized option keywords are:
668 =item B<-expand_seq> =E<gt> I<code-ref>|I<method-name>
670 Normally, the parse-tree returned by B<parse_text()> will contain an
671 unexpanded C<Pod::InteriorSequence> object for each interior-sequence
672 encountered. Specifying B<-expand_seq> tells B<parse_text()> to "expand"
673 every interior-sequence it sees by invoking the referenced function
674 (or named method of the parser object) and using the return value as the
677 If a subroutine reference was given, it is invoked as:
679 &$code_ref( $parser, $sequence )
681 and if a method-name was given, it is invoked as:
683 $parser->method_name( $sequence )
685 where C<$parser> is a reference to the parser object, and C<$sequence>
686 is a reference to the interior-sequence object.
687 [I<NOTE>: If the B<interior_sequence()> method is specified, then it is
688 invoked according to the interface specified in L<"interior_sequence()">].
690 =item B<-expand_text> =E<gt> I<code-ref>|I<method-name>
692 Normally, the parse-tree returned by B<parse_text()> will contain a
693 text-string for each contiguous sequence of characters outside of an
694 interior-sequence. Specifying B<-expand_text> tells B<parse_text()> to
695 "preprocess" every such text-string it sees by invoking the referenced
696 function (or named method of the parser object) and using the return value
697 as the preprocessed (or "expanded") result. [Note that if the result is
698 an interior-sequence, then it will I<not> be expanded as specified by the
699 B<-expand_seq> option; Any such recursive expansion needs to be handled by
700 the specified callback routine.]
702 If a subroutine reference was given, it is invoked as:
704 &$code_ref( $parser, $text, $ptree_node )
706 and if a method-name was given, it is invoked as:
708 $parser->method_name( $text, $ptree_node )
710 where C<$parser> is a reference to the parser object, C<$text> is the
711 text-string encountered, and C<$ptree_node> is a reference to the current
712 node in the parse-tree (usually an interior-sequence object or else the
713 top-level node of the parse-tree).
715 =item B<-expand_ptree> =E<gt> I<code-ref>|I<method-name>
717 Rather than returning a C<Pod::ParseTree>, pass the parse-tree as an
718 argument to the referenced subroutine (or named method of the parser
719 object) and return the result instead of the parse-tree object.
721 If a subroutine reference was given, it is invoked as:
723 &$code_ref( $parser, $ptree )
725 and if a method-name was given, it is invoked as:
727 $parser->method_name( $ptree )
729 where C<$parser> is a reference to the parser object, and C<$ptree>
730 is a reference to the parse-tree object.
740 ## Get options and set any defaults
741 my %opts = (ref $_[0]) ? %{ shift() } : ();
742 my $expand_seq = $opts{'-expand_seq'} || undef;
743 my $expand_text = $opts{'-expand_text'} || undef;
744 my $expand_ptree = $opts{'-expand_ptree'} || undef;
748 my $file = $self->input_file();
751 ## Convert method calls into closures, for our convenience
752 my $xseq_sub = $expand_seq;
753 my $xtext_sub = $expand_text;
754 my $xptree_sub = $expand_ptree;
755 if (defined $expand_seq and $expand_seq eq 'interior_sequence') {
756 ## If 'interior_sequence' is the method to use, we have to pass
757 ## more than just the sequence object, we also need to pass the
758 ## sequence name and text.
760 my ($self, $iseq) = @_;
761 my $args = join("", $iseq->parse_tree->children);
762 return $self->interior_sequence($iseq->name, $args, $iseq);
765 ref $xseq_sub or $xseq_sub = sub { shift()->$expand_seq(@_) };
766 ref $xtext_sub or $xtext_sub = sub { shift()->$expand_text(@_) };
767 ref $xptree_sub or $xptree_sub = sub { shift()->$expand_ptree(@_) };
769 ## Keep track of the "current" interior sequence, and maintain a stack
770 ## of "in progress" sequences.
772 ## NOTE that we push our own "accumulator" at the very beginning of the
773 ## stack. It's really a parse-tree, not a sequence; but it implements
774 ## the methods we need so we can use it to gather-up all the sequences
775 ## and strings we parse. Thus, by the end of our parsing, it should be
776 ## the only thing left on our stack and all we have to do is return it!
778 my $seq = Pod::ParseTree->new();
779 my @seq_stack = ($seq);
780 my ($ldelim, $rdelim) = ('', '');
782 ## Iterate over all sequence starts text (NOTE: split with
783 ## capturing parens keeps the delimiters)
785 my @tokens = split /([A-Z]<(?:<+\s)?)/;
788 ## Look for the beginning of a sequence
789 if ( /^([A-Z])(<(?:<+\s)?)$/ ) {
790 ## Push a new sequence onto the stack of those "in-progress"
792 ($cmd, $ldelim_orig) = ($1, $2);
793 ($ldelim = $ldelim_orig) =~ s/\s+$//;
794 ($rdelim = $ldelim) =~ tr/</>/;
795 $seq = Pod::InteriorSequence->new(
797 -ldelim => $ldelim_orig, -rdelim => $rdelim,
798 -file => $file, -line => $line
800 (@seq_stack > 1) and $seq->nested($seq_stack[-1]);
801 push @seq_stack, $seq;
803 ## Look for sequence ending
804 elsif ( @seq_stack > 1 ) {
805 ## Make sure we match the right kind of closing delimiter
806 my ($seq_end, $post_seq) = ("", "");
807 if ( ($ldelim eq '<' and /\A(.*?)(>)/s)
808 or /\A(.*?)(\s+$rdelim)/s )
810 ## Found end-of-sequence, capture the interior and the
811 ## closing the delimiter, and put the rest back on the
813 $post_seq = substr($_, length($1) + length($2));
814 ($_, $seq_end) = ($1, $2);
815 (length $post_seq) and unshift @tokens, $post_seq;
818 ## In the middle of a sequence, append this text to it, and
819 ## dont forget to "expand" it if that's what the caller wanted
820 $seq->append($expand_text ? &$xtext_sub($self,$_,$seq) : $_);
823 if (length $seq_end) {
824 ## End of current sequence, record terminating delimiter
825 $seq->rdelim($seq_end);
826 ## Pop it off the stack of "in progress" sequences
828 ## Append result to its parent in current parse tree
829 $seq_stack[-1]->append($expand_seq ? &$xseq_sub($self,$seq)
831 ## Remember the current cmd-name and left-delimiter
833 $cmd = $seq_stack[-1]->name;
834 $ldelim = $seq_stack[-1]->ldelim;
835 $rdelim = $seq_stack[-1]->rdelim;
837 $cmd = $ldelim = $rdelim = '';
842 ## In the middle of a sequence, append this text to it, and
843 ## dont forget to "expand" it if that's what the caller wanted
844 $seq->append($expand_text ? &$xtext_sub($self,$_,$seq) : $_);
846 ## Keep track of line count
848 ## Remember the "current" sequence
849 $seq = $seq_stack[-1];
852 ## Handle unterminated sequences
853 my $errorsub = (@seq_stack > 1) ? $self->errorsub() : undef;
854 while (@seq_stack > 1) {
855 ($cmd, $file, $line) = ($seq->name, $seq->file_line);
856 $ldelim = $seq->ldelim;
857 ($rdelim = $ldelim) =~ tr/</>/;
858 $rdelim =~ s/^(\S+)(\s*)$/$2$1/;
860 my $errmsg = "*** ERROR: unterminated ${cmd}${ldelim}...${rdelim}".
861 " at line $line in file $file\n";
862 (ref $errorsub) and &{$errorsub}($errmsg)
863 or (defined $errorsub) and $self->$errorsub($errmsg)
865 $seq_stack[-1]->append($expand_seq ? &$xseq_sub($self,$seq) : $seq);
866 $seq = $seq_stack[-1];
869 ## Return the resulting parse-tree
870 my $ptree = (pop @seq_stack)->parse_tree;
871 return $expand_ptree ? &$xptree_sub($self, $ptree) : $ptree;
874 ##---------------------------------------------------------------------------
876 =head1 B<interpolate()>
878 $textblock = $parser->interpolate($text, $line_num);
880 This method translates all text (including any embedded interior sequences)
881 in the given text string C<$text> and returns the interpolated result. The
882 parameter C<$line_num> is the line number corresponding to the beginning
885 B<interpolate()> merely invokes a private method to recursively expand
886 nested interior sequences in bottom-up order (innermost sequences are
887 expanded first). If there is a need to expand nested sequences in
888 some alternate order, use B<parse_text> instead.
893 my($self, $text, $line_num) = @_;
894 my %parse_opts = ( -expand_seq => 'interior_sequence' );
895 my $ptree = $self->parse_text( \%parse_opts, $text, $line_num );
896 return join "", $ptree->children();
899 ##---------------------------------------------------------------------------
903 =head1 B<parse_paragraph()>
905 $parser->parse_paragraph($text, $line_num);
907 This method takes the text of a POD paragraph to be processed, along
908 with its corresponding line number, and invokes the appropriate method
909 (one of B<command()>, B<verbatim()>, or B<textblock()>).
911 For performance reasons, this method is invoked directly without any
912 dynamic lookup; Hence subclasses may I<not> override it!
918 sub parse_paragraph {
919 my ($self, $text, $line_num) = @_;
920 local *myData = $self; ## alias to avoid deref-ing overhead
921 local *myOpts = ($myData{_PARSEOPTS} ||= {}); ## get parse-options
924 ## See if we want to preprocess nonPOD paragraphs as well as POD ones.
925 my $wantNonPods = $myOpts{'-want_nonPODs'};
927 ## Update cutting status
928 $myData{_CUTTING} = 0 if $text =~ /^={1,2}\S/;
930 ## Perform any desired preprocessing if we wanted it this early
931 $wantNonPods and $text = $self->preprocess_paragraph($text, $line_num);
933 ## Ignore up until next POD directive if we are cutting
934 return if $myData{_CUTTING};
936 ## Now we know this is block of text in a POD section!
938 ##-----------------------------------------------------------------
939 ## This is a hook (hack ;-) for Pod::Select to do its thing without
940 ## having to override methods, but also without Pod::Parser assuming
941 ## $self is an instance of Pod::Select (if the _SELECTED_SECTIONS
942 ## field exists then we assume there is an is_selected() method for
943 ## us to invoke (calling $self->can('is_selected') could verify this
944 ## but that is more overhead than I want to incur)
945 ##-----------------------------------------------------------------
947 ## Ignore this block if it isnt in one of the selected sections
948 if (exists $myData{_SELECTED_SECTIONS}) {
949 $self->is_selected($text) or return ($myData{_CUTTING} = 1);
952 ## If we havent already, perform any desired preprocessing and
953 ## then re-check the "cutting" state
954 unless ($wantNonPods) {
955 $text = $self->preprocess_paragraph($text, $line_num);
956 return 1 unless ((defined $text) and (length $text));
957 return 1 if ($myData{_CUTTING});
960 ## Look for one of the three types of paragraphs
961 my ($pfx, $cmd, $arg, $sep) = ('', '', '', '');
962 my $pod_para = undef;
963 if ($text =~ /^(={1,2})(?=\S)/) {
964 ## Looks like a command paragraph. Capture the command prefix used
965 ## ("=" or "=="), as well as the command-name, its paragraph text,
966 ## and whatever sequence of characters was used to separate them
968 $_ = substr($text, length $pfx);
969 ($cmd, $sep, $text) = split /(\s+)/, $_, 2;
970 ## If this is a "cut" directive then we dont need to do anything
971 ## except return to "cutting" mode.
973 $myData{_CUTTING} = 1;
974 return unless $myOpts{'-process_cut_cmd'};
977 ## Save the attributes indicating how the command was specified.
978 $pod_para = new Pod::Paragraph(
983 -file => $myData{_INFILE},
986 # ## Invoke appropriate callbacks
987 # if (exists $myData{_CALLBACKS}) {
988 # ## Look through the callback list, invoke callbacks,
989 # ## then see if we need to do the default actions
990 # ## (invoke_callbacks will return true if we do).
991 # return 1 unless $self->invoke_callbacks($cmd, $text, $line_num, $pod_para);
994 ## A command paragraph
995 $self->command($cmd, $text, $line_num, $pod_para);
997 elsif ($text =~ /^\s+/) {
998 ## Indented text - must be a verbatim paragraph
999 $self->verbatim($text, $line_num, $pod_para);
1002 ## Looks like an ordinary block of text
1003 $self->textblock($text, $line_num, $pod_para);
1008 ##---------------------------------------------------------------------------
1010 =head1 B<parse_from_filehandle()>
1012 $parser->parse_from_filehandle($in_fh,$out_fh);
1014 This method takes an input filehandle (which is assumed to already be
1015 opened for reading) and reads the entire input stream looking for blocks
1016 (paragraphs) of POD documentation to be processed. If no first argument
1017 is given the default input filehandle C<STDIN> is used.
1019 The C<$in_fh> parameter may be any object that provides a B<getline()>
1020 method to retrieve a single line of input text (hence, an appropriate
1021 wrapper object could be used to parse PODs from a single string or an
1024 Using C<$in_fh-E<gt>getline()>, input is read line-by-line and assembled
1025 into paragraphs or "blocks" (which are separated by lines containing
1026 nothing but whitespace). For each block of POD documentation
1027 encountered it will invoke a method to parse the given paragraph.
1029 If a second argument is given then it should correspond to a filehandle where
1030 output should be sent (otherwise the default output filehandle is
1031 C<STDOUT> if no output filehandle is currently in use).
1033 B<NOTE:> For performance reasons, this method caches the input stream at
1034 the top of the stack in a local variable. Any attempts by clients to
1035 change the stack contents during processing when in the midst executing
1036 of this method I<will not affect> the input stream used by the current
1037 invocation of this method.
1039 This method does I<not> usually need to be overridden by subclasses.
1043 sub parse_from_filehandle {
1045 my %opts = (ref $_[0] eq 'HASH') ? %{ shift() } : ();
1046 my ($in_fh, $out_fh) = @_;
1047 $in_fh = \*STDIN unless ($in_fh);
1048 local *myData = $self; ## alias to avoid deref-ing overhead
1049 local *myOpts = ($myData{_PARSEOPTS} ||= {}); ## get parse-options
1052 ## Put this stream at the top of the stack and do beginning-of-input
1053 ## processing. NOTE that $in_fh might be reset during this process.
1054 my $topstream = $self->_push_input_stream($in_fh, $out_fh);
1055 (exists $opts{-cutting}) and $self->cutting( $opts{-cutting} );
1057 ## Initialize line/paragraph
1058 my ($textline, $paragraph) = ('', '');
1059 my ($nlines, $plines) = (0, 0);
1061 ## Use <$fh> instead of $fh->getline where possible (for speed)
1063 my $tied_fh = (/^(?:GLOB|FileHandle|IO::\w+)$/ or tied $in_fh);
1065 ## Read paragraphs line-by-line
1066 while (defined ($textline = $tied_fh ? <$in_fh> : $in_fh->getline)) {
1067 $textline = $self->preprocess_line($textline, ++$nlines);
1068 next unless ((defined $textline) && (length $textline));
1069 $_ = $paragraph; ## save previous contents
1071 if ((! length $paragraph) && ($textline =~ /^==/)) {
1072 ## '==' denotes a one-line command paragraph
1073 $paragraph = $textline;
1077 ## Append this line to the current paragraph
1078 $paragraph .= $textline;
1082 ## See if this line is blank and ends the current paragraph.
1083 ## If it isnt, then keep iterating until it is.
1084 next unless (($textline =~ /^([^\S\r\n]*)[\r\n]*$/)
1085 && (length $paragraph));
1087 ## Issue a warning about any non-empty blank lines
1088 if (length($1) > 0 and $myOpts{'-warnings'} and ! $myData{_CUTTING}) {
1089 my $errorsub = $self->errorsub();
1090 my $file = $self->input_file();
1091 my $errmsg = "*** WARNING: line containing nothing but whitespace".
1092 " in paragraph at line $nlines in file $file\n";
1093 (ref $errorsub) and &{$errorsub}($errmsg)
1094 or (defined $errorsub) and $self->$errorsub($errmsg)
1098 ## Now process the paragraph
1099 parse_paragraph($self, $paragraph, ($nlines - $plines) + 1);
1103 ## Dont forget about the last paragraph in the file
1104 if (length $paragraph) {
1105 parse_paragraph($self, $paragraph, ($nlines - $plines) + 1)
1108 ## Now pop the input stream off the top of the input stack.
1109 $self->_pop_input_stream();
1112 ##---------------------------------------------------------------------------
1114 =head1 B<parse_from_file()>
1116 $parser->parse_from_file($filename,$outfile);
1118 This method takes a filename and does the following:
1124 opens the input and output files for reading
1125 (creating the appropriate filehandles)
1129 invokes the B<parse_from_filehandle()> method passing it the
1130 corresponding input and output filehandles.
1134 closes the input and output files.
1138 If the special input filename "-" or "<&STDIN" is given then the STDIN
1139 filehandle is used for input (and no open or close is performed). If no
1140 input filename is specified then "-" is implied.
1142 If a second argument is given then it should be the name of the desired
1143 output file. If the special output filename "-" or ">&STDOUT" is given
1144 then the STDOUT filehandle is used for output (and no open or close is
1145 performed). If the special output filename ">&STDERR" is given then the
1146 STDERR filehandle is used for output (and no open or close is
1147 performed). If no output filehandle is currently in use and no output
1148 filename is specified, then "-" is implied.
1150 This method does I<not> usually need to be overridden by subclasses.
1154 sub parse_from_file {
1156 my %opts = (ref $_[0] eq 'HASH') ? %{ shift() } : ();
1157 my ($infile, $outfile) = @_;
1158 my ($in_fh, $out_fh) = (gensym, gensym) if ($] < 5.6);
1159 my ($close_input, $close_output) = (0, 0);
1160 local *myData = $self;
1163 ## Is $infile a filename or a (possibly implied) filehandle
1164 $infile = '-' unless ((defined $infile) && (length $infile));
1165 if (($infile eq '-') || ($infile =~ /^<&(STDIN|0)$/i)) {
1166 ## Not a filename, just a string implying STDIN
1167 $myData{_INFILE} = "<standard input>";
1170 elsif (ref $infile) {
1171 ## Must be a filehandle-ref (or else assume its a ref to an object
1172 ## that supports the common IO read operations).
1173 $myData{_INFILE} = ${$infile};
1177 ## We have a filename, open it for reading
1178 $myData{_INFILE} = $infile;
1179 open($in_fh, "< $infile") or
1180 croak "Can't open $infile for reading: $!\n";
1184 ## NOTE: we need to be *very* careful when "defaulting" the output
1185 ## file. We only want to use a default if this is the beginning of
1186 ## the entire document (but *not* if this is an included file). We
1187 ## determine this by seeing if the input stream stack has been set-up
1190 unless ((defined $outfile) && (length $outfile)) {
1191 (defined $myData{_TOP_STREAM}) && ($out_fh = $myData{_OUTPUT})
1192 || ($outfile = '-');
1194 ## Is $outfile a filename or a (possibly implied) filehandle
1195 if ((defined $outfile) && (length $outfile)) {
1196 if (($outfile eq '-') || ($outfile =~ /^>&?(?:STDOUT|1)$/i)) {
1197 ## Not a filename, just a string implying STDOUT
1198 $myData{_OUTFILE} = "<standard output>";
1201 elsif ($outfile =~ /^>&(STDERR|2)$/i) {
1202 ## Not a filename, just a string implying STDERR
1203 $myData{_OUTFILE} = "<standard error>";
1206 elsif (ref $outfile) {
1207 ## Must be a filehandle-ref (or else assume its a ref to an
1208 ## object that supports the common IO write operations).
1209 $myData{_OUTFILE} = ${$outfile};
1213 ## We have a filename, open it for writing
1214 $myData{_OUTFILE} = $outfile;
1215 (-d $outfile) and croak "$outfile is a directory, not POD input!\n";
1216 open($out_fh, "> $outfile") or
1217 croak "Can't open $outfile for writing: $!\n";
1222 ## Whew! That was a lot of work to set up reasonably/robust behavior
1223 ## in the case of a non-filename for reading and writing. Now we just
1224 ## have to parse the input and close the handles when we're finished.
1225 $self->parse_from_filehandle(\%opts, $in_fh, $out_fh);
1228 close($in_fh) || croak "Can't close $infile after reading: $!\n";
1230 close($out_fh) || croak "Can't close $outfile after writing: $!\n";
1233 #############################################################################
1235 =head1 ACCESSOR METHODS
1237 Clients of B<Pod::Parser> should use the following methods to access
1238 instance data fields:
1242 ##---------------------------------------------------------------------------
1244 =head1 B<errorsub()>
1246 $parser->errorsub("method_name");
1247 $parser->errorsub(\&warn_user);
1248 $parser->errorsub(sub { print STDERR, @_ });
1250 Specifies the method or subroutine to use when printing error messages
1251 about POD syntax. The supplied method/subroutine I<must> return TRUE upon
1252 successful printing of the message. If C<undef> is given, then the B<warn>
1253 builtin is used to issue error messages (this is the default behavior).
1255 my $errorsub = $parser->errorsub()
1256 my $errmsg = "This is an error message!\n"
1257 (ref $errorsub) and &{$errorsub}($errmsg)
1258 or (defined $errorsub) and $parser->$errorsub($errmsg)
1261 Returns a method name, or else a reference to the user-supplied subroutine
1262 used to print error messages. Returns C<undef> if the B<warn> builtin
1263 is used to issue error messages (this is the default behavior).
1268 return (@_ > 1) ? ($_[0]->{_ERRORSUB} = $_[1]) : $_[0]->{_ERRORSUB};
1271 ##---------------------------------------------------------------------------
1275 $boolean = $parser->cutting();
1277 Returns the current C<cutting> state: a boolean-valued scalar which
1278 evaluates to true if text from the input file is currently being "cut"
1279 (meaning it is I<not> considered part of the POD document).
1281 $parser->cutting($boolean);
1283 Sets the current C<cutting> state to the given value and returns the
1289 return (@_ > 1) ? ($_[0]->{_CUTTING} = $_[1]) : $_[0]->{_CUTTING};
1292 ##---------------------------------------------------------------------------
1294 ##---------------------------------------------------------------------------
1296 =head1 B<parseopts()>
1298 When invoked with no additional arguments, B<parseopts> returns a hashtable
1299 of all the current parsing options.
1301 ## See if we are parsing non-POD sections as well as POD ones
1302 my %opts = $parser->parseopts();
1303 $opts{'-want_nonPODs}' and print "-want_nonPODs\n";
1305 When invoked using a single string, B<parseopts> treats the string as the
1306 name of a parse-option and returns its corresponding value if it exists
1307 (returns C<undef> if it doesn't).
1309 ## Did we ask to see '=cut' paragraphs?
1310 my $want_cut = $parser->parseopts('-process_cut_cmd');
1311 $want_cut and print "-process_cut_cmd\n";
1313 When invoked with multiple arguments, B<parseopts> treats them as
1314 key/value pairs and the specified parse-option names are set to the
1315 given values. Any unspecified parse-options are unaffected.
1317 ## Set them back to the default
1318 $parser->parseopts(-warnings => 0);
1320 When passed a single hash-ref, B<parseopts> uses that hash to completely
1321 reset the existing parse-options, all previous parse-option values
1324 ## Reset all options to default
1325 $parser->parseopts( { } );
1327 See L<"PARSING OPTIONS"> for more information on the name and meaning of each
1328 parse-option currently recognized.
1333 local *myData = shift;
1334 local *myOpts = ($myData{_PARSEOPTS} ||= {});
1335 return %myOpts if (@_ == 0);
1338 return ref($_) ? $myData{_PARSEOPTS} = $_ : $myOpts{$_};
1340 my @newOpts = (%myOpts, @_);
1341 $myData{_PARSEOPTS} = { @newOpts };
1344 ##---------------------------------------------------------------------------
1346 =head1 B<output_file()>
1348 $fname = $parser->output_file();
1350 Returns the name of the output file being written.
1355 return $_[0]->{_OUTFILE};
1358 ##---------------------------------------------------------------------------
1360 =head1 B<output_handle()>
1362 $fhandle = $parser->output_handle();
1364 Returns the output filehandle object.
1369 return $_[0]->{_OUTPUT};
1372 ##---------------------------------------------------------------------------
1374 =head1 B<input_file()>
1376 $fname = $parser->input_file();
1378 Returns the name of the input file being read.
1383 return $_[0]->{_INFILE};
1386 ##---------------------------------------------------------------------------
1388 =head1 B<input_handle()>
1390 $fhandle = $parser->input_handle();
1392 Returns the current input filehandle object.
1397 return $_[0]->{_INPUT};
1400 ##---------------------------------------------------------------------------
1404 =head1 B<input_streams()>
1406 $listref = $parser->input_streams();
1408 Returns a reference to an array which corresponds to the stack of all
1409 the input streams that are currently in the middle of being parsed.
1411 While parsing an input stream, it is possible to invoke
1412 B<parse_from_file()> or B<parse_from_filehandle()> to parse a new input
1413 stream and then return to parsing the previous input stream. Each input
1414 stream to be parsed is pushed onto the end of this input stack
1415 before any of its input is read. The input stream that is currently
1416 being parsed is always at the end (or top) of the input stack. When an
1417 input stream has been exhausted, it is popped off the end of the
1420 Each element on this input stack is a reference to C<Pod::InputSource>
1421 object. Please see L<Pod::InputObjects> for more details.
1423 This method might be invoked when printing diagnostic messages, for example,
1424 to obtain the name and line number of the all input files that are currently
1432 return $_[0]->{_INPUT_STREAMS};
1435 ##---------------------------------------------------------------------------
1439 =head1 B<top_stream()>
1441 $hashref = $parser->top_stream();
1443 Returns a reference to the hash-table that represents the element
1444 that is currently at the top (end) of the input stream stack
1445 (see L<"input_streams()">). The return value will be the C<undef>
1446 if the input stack is empty.
1448 This method might be used when printing diagnostic messages, for example,
1449 to obtain the name and line number of the current input file.
1456 return $_[0]->{_TOP_STREAM} || undef;
1459 #############################################################################
1461 =head1 PRIVATE METHODS AND DATA
1463 B<Pod::Parser> makes use of several internal methods and data fields
1464 which clients should not need to see or use. For the sake of avoiding
1465 name collisions for client data and methods, these methods and fields
1466 are briefly discussed here. Determined hackers may obtain further
1467 information about them by reading the B<Pod::Parser> source code.
1469 Private data fields are stored in the hash-object whose reference is
1470 returned by the B<new()> constructor for this class. The names of all
1471 private methods and data-fields used by B<Pod::Parser> begin with a
1472 prefix of "_" and match the regular expression C</^_\w+$/>.
1476 ##---------------------------------------------------------------------------
1480 =head1 B<_push_input_stream()>
1482 $hashref = $parser->_push_input_stream($in_fh,$out_fh);
1484 This method will push the given input stream on the input stack and
1485 perform any necessary beginning-of-document or beginning-of-file
1486 processing. The argument C<$in_fh> is the input stream filehandle to
1487 push, and C<$out_fh> is the corresponding output filehandle to use (if
1488 it is not given or is undefined, then the current output stream is used,
1489 which defaults to standard output if it doesnt exist yet).
1491 The value returned will be reference to the hash-table that represents
1492 the new top of the input stream stack. I<Please Note> that it is
1493 possible for this method to use default values for the input and output
1494 file handles. If this happens, you will need to look at the C<INPUT>
1495 and C<OUTPUT> instance data members to determine their new values.
1501 sub _push_input_stream {
1502 my ($self, $in_fh, $out_fh) = @_;
1503 local *myData = $self;
1505 ## Initialize stuff for the entire document if this is *not*
1506 ## an included file.
1508 ## NOTE: we need to be *very* careful when "defaulting" the output
1509 ## filehandle. We only want to use a default value if this is the
1510 ## beginning of the entire document (but *not* if this is an included
1512 unless (defined $myData{_TOP_STREAM}) {
1513 $out_fh = \*STDOUT unless (defined $out_fh);
1514 $myData{_CUTTING} = 1; ## current "cutting" state
1515 $myData{_INPUT_STREAMS} = []; ## stack of all input streams
1518 ## Initialize input indicators
1519 $myData{_OUTFILE} = '(unknown)' unless (defined $myData{_OUTFILE});
1520 $myData{_OUTPUT} = $out_fh if (defined $out_fh);
1521 $in_fh = \*STDIN unless (defined $in_fh);
1522 $myData{_INFILE} = '(unknown)' unless (defined $myData{_INFILE});
1523 $myData{_INPUT} = $in_fh;
1524 my $input_top = $myData{_TOP_STREAM}
1525 = new Pod::InputSource(
1526 -name => $myData{_INFILE},
1528 -was_cutting => $myData{_CUTTING}
1530 local *input_stack = $myData{_INPUT_STREAMS};
1531 push(@input_stack, $input_top);
1533 ## Perform beginning-of-document and/or beginning-of-input processing
1534 $self->begin_pod() if (@input_stack == 1);
1535 $self->begin_input();
1540 ##---------------------------------------------------------------------------
1544 =head1 B<_pop_input_stream()>
1546 $hashref = $parser->_pop_input_stream();
1548 This takes no arguments. It will perform any necessary end-of-file or
1549 end-of-document processing and then pop the current input stream from
1550 the top of the input stack.
1552 The value returned will be reference to the hash-table that represents
1553 the new top of the input stream stack.
1559 sub _pop_input_stream {
1561 local *myData = $self;
1562 local *input_stack = $myData{_INPUT_STREAMS};
1564 ## Perform end-of-input and/or end-of-document processing
1565 $self->end_input() if (@input_stack > 0);
1566 $self->end_pod() if (@input_stack == 1);
1568 ## Restore cutting state to whatever it was before we started
1569 ## parsing this file.
1570 my $old_top = pop(@input_stack);
1571 $myData{_CUTTING} = $old_top->was_cutting();
1573 ## Dont forget to reset the input indicators
1574 my $input_top = undef;
1575 if (@input_stack > 0) {
1576 $input_top = $myData{_TOP_STREAM} = $input_stack[-1];
1577 $myData{_INFILE} = $input_top->name();
1578 $myData{_INPUT} = $input_top->handle();
1580 delete $myData{_TOP_STREAM};
1581 delete $myData{_INPUT_STREAMS};
1587 #############################################################################
1589 =head1 TREE-BASED PARSING
1591 If straightforward stream-based parsing wont meet your needs (as is
1592 likely the case for tasks such as translating PODs into structured
1593 markup languages like HTML and XML) then you may need to take the
1594 tree-based approach. Rather than doing everything in one pass and
1595 calling the B<interpolate()> method to expand sequences into text, it
1596 may be desirable to instead create a parse-tree using the B<parse_text()>
1597 method to return a tree-like structure which may contain an ordered
1598 list of children (each of which may be a text-string, or a similar
1599 tree-like structure).
1601 Pay special attention to L<"METHODS FOR PARSING AND PROCESSING"> and
1602 to the objects described in L<Pod::InputObjects>. The former describes
1603 the gory details and parameters for how to customize and extend the
1604 parsing behavior of B<Pod::Parser>. B<Pod::InputObjects> provides
1605 several objects that may all be used interchangeably as parse-trees. The
1606 most obvious one is the B<Pod::ParseTree> object. It defines the basic
1607 interface and functionality that all things trying to be a POD parse-tree
1608 should do. A B<Pod::ParseTree> is defined such that each "node" may be a
1609 text-string, or a reference to another parse-tree. Each B<Pod::Paragraph>
1610 object and each B<Pod::InteriorSequence> object also supports the basic
1611 parse-tree interface.
1613 The B<parse_text()> method takes a given paragraph of text, and
1614 returns a parse-tree that contains one or more children, each of which
1615 may be a text-string, or an InteriorSequence object. There are also
1616 callback-options that may be passed to B<parse_text()> to customize
1617 the way it expands or transforms interior-sequences, as well as the
1618 returned result. These callbacks can be used to create a parse-tree
1619 with custom-made objects (which may or may not support the parse-tree
1620 interface, depending on how you choose to do it).
1622 If you wish to turn an entire POD document into a parse-tree, that process
1623 is fairly straightforward. The B<parse_text()> method is the key to doing
1624 this successfully. Every paragraph-callback (i.e. the polymorphic methods
1625 for B<command()>, B<verbatim()>, and B<textblock()> paragraphs) takes
1626 a B<Pod::Paragraph> object as an argument. Each paragraph object has a
1627 B<parse_tree()> method that can be used to get or set a corresponding
1628 parse-tree. So for each of those paragraph-callback methods, simply call
1629 B<parse_text()> with the options you desire, and then use the returned
1630 parse-tree to assign to the given paragraph object.
1632 That gives you a parse-tree for each paragraph - so now all you need is
1633 an ordered list of paragraphs. You can maintain that yourself as a data
1634 element in the object/hash. The most straightforward way would be simply
1635 to use an array-ref, with the desired set of custom "options" for each
1636 invocation of B<parse_text>. Let's assume the desired option-set is
1637 given by the hash C<%options>. Then we might do something like the
1640 package MyPodParserTree;
1642 @ISA = qw( Pod::Parser );
1648 $self->{'-paragraphs'} = []; ## initialize paragraph list
1652 my ($parser, $command, $paragraph, $line_num, $pod_para) = @_;
1653 my $ptree = $parser->parse_text({%options}, $paragraph, ...);
1654 $pod_para->parse_tree( $ptree );
1655 push @{ $self->{'-paragraphs'} }, $pod_para;
1659 my ($parser, $paragraph, $line_num, $pod_para) = @_;
1660 push @{ $self->{'-paragraphs'} }, $pod_para;
1664 my ($parser, $paragraph, $line_num, $pod_para) = @_;
1665 my $ptree = $parser->parse_text({%options}, $paragraph, ...);
1666 $pod_para->parse_tree( $ptree );
1667 push @{ $self->{'-paragraphs'} }, $pod_para;
1674 my $parser = new MyPodParserTree(...);
1675 $parser->parse_from_file(...);
1676 my $paragraphs_ref = $parser->{'-paragraphs'};
1678 Of course, in this module-author's humble opinion, I'd be more inclined to
1679 use the existing B<Pod::ParseTree> object than a simple array. That way
1680 everything in it, paragraphs and sequences, all respond to the same core
1681 interface for all parse-tree nodes. The result would look something like:
1683 package MyPodParserTree2;
1689 $self->{'-ptree'} = new Pod::ParseTree; ## initialize parse-tree
1693 ## convenience method to get/set the parse-tree for the entire POD
1694 (@_ > 1) and $_[0]->{'-ptree'} = $_[1];
1695 return $_[0]->{'-ptree'};
1699 my ($parser, $command, $paragraph, $line_num, $pod_para) = @_;
1700 my $ptree = $parser->parse_text({<<options>>}, $paragraph, ...);
1701 $pod_para->parse_tree( $ptree );
1702 $parser->parse_tree()->append( $pod_para );
1706 my ($parser, $paragraph, $line_num, $pod_para) = @_;
1707 $parser->parse_tree()->append( $pod_para );
1711 my ($parser, $paragraph, $line_num, $pod_para) = @_;
1712 my $ptree = $parser->parse_text({<<options>>}, $paragraph, ...);
1713 $pod_para->parse_tree( $ptree );
1714 $parser->parse_tree()->append( $pod_para );
1721 my $parser = new MyPodParserTree2(...);
1722 $parser->parse_from_file(...);
1723 my $ptree = $parser->parse_tree;
1726 Now you have the entire POD document as one great big parse-tree. You
1727 can even use the B<-expand_seq> option to B<parse_text> to insert
1728 whole different kinds of objects. Just don't expect B<Pod::Parser>
1729 to know what to do with them after that. That will need to be in your
1730 code. Or, alternatively, you can insert any object you like so long as
1731 it conforms to the B<Pod::ParseTree> interface.
1733 One could use this to create subclasses of B<Pod::Paragraphs> and
1734 B<Pod::InteriorSequences> for specific commands (or to create your own
1735 custom node-types in the parse-tree) and add some kind of B<emit()>
1736 method to each custom node/subclass object in the tree. Then all you'd
1737 need to do is recursively walk the tree in the desired order, processing
1738 the children (most likely from left to right) by formatting them if
1739 they are text-strings, or by calling their B<emit()> method if they
1740 are objects/references.
1744 L<Pod::InputObjects>, L<Pod::Select>
1746 B<Pod::InputObjects> defines POD input objects corresponding to
1747 command paragraphs, parse-trees, and interior-sequences.
1749 B<Pod::Select> is a subclass of B<Pod::Parser> which provides the ability
1750 to selectively include and/or exclude sections of a POD document from being
1751 translated based upon the current heading, subheading, subsubheading, etc.
1754 B<Pod::Callbacks> is a subclass of B<Pod::Parser> which gives its users
1755 the ability the employ I<callback functions> instead of, or in addition
1756 to, overriding methods of the base class.
1759 B<Pod::Select> and B<Pod::Callbacks> do not override any
1760 methods nor do they define any new methods with the same name. Because
1761 of this, they may I<both> be used (in combination) as a base class of
1762 the same subclass in order to combine their functionality without
1763 causing any namespace clashes due to multiple inheritance.
1767 Please report bugs using L<http://rt.cpan.org>.
1769 Brad Appleton E<lt>bradapp@enteract.comE<gt>
1771 Based on code for B<Pod::Text> written by
1772 Tom Christiansen E<lt>tchrist@mox.perl.comE<gt>