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 $VERSION = 1.35; ## Current version of this package
14 require 5.005; ## requires this Perl version or later
16 #############################################################################
20 Pod::Parser - base class for creating POD filters and translators
27 @ISA = qw(Pod::Parser);
30 my ($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 interpret 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<$line_num> is the
654 line number corresponding to the beginning of C<$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));
1070 if ((! length $paragraph) && ($textline =~ /^==/)) {
1071 ## '==' denotes a one-line command paragraph
1072 $paragraph = $textline;
1076 ## Append this line to the current paragraph
1077 $paragraph .= $textline;
1081 ## See if this line is blank and ends the current paragraph.
1082 ## If it isnt, then keep iterating until it is.
1083 next unless (($textline =~ /^([^\S\r\n]*)[\r\n]*$/)
1084 && (length $paragraph));
1086 ## Issue a warning about any non-empty blank lines
1087 if (length($1) > 0 and $myOpts{'-warnings'} and ! $myData{_CUTTING}) {
1088 my $errorsub = $self->errorsub();
1089 my $file = $self->input_file();
1090 my $errmsg = "*** WARNING: line containing nothing but whitespace".
1091 " in paragraph at line $nlines in file $file\n";
1092 (ref $errorsub) and &{$errorsub}($errmsg)
1093 or (defined $errorsub) and $self->$errorsub($errmsg)
1097 ## Now process the paragraph
1098 parse_paragraph($self, $paragraph, ($nlines - $plines) + 1);
1102 ## Dont forget about the last paragraph in the file
1103 if (length $paragraph) {
1104 parse_paragraph($self, $paragraph, ($nlines - $plines) + 1)
1107 ## Now pop the input stream off the top of the input stack.
1108 $self->_pop_input_stream();
1111 ##---------------------------------------------------------------------------
1113 =head1 B<parse_from_file()>
1115 $parser->parse_from_file($filename,$outfile);
1117 This method takes a filename and does the following:
1123 opens the input and output files for reading
1124 (creating the appropriate filehandles)
1128 invokes the B<parse_from_filehandle()> method passing it the
1129 corresponding input and output filehandles.
1133 closes the input and output files.
1137 If the special input filename "-" or "<&STDIN" is given then the STDIN
1138 filehandle is used for input (and no open or close is performed). If no
1139 input filename is specified then "-" is implied.
1141 If a second argument is given then it should be the name of the desired
1142 output file. If the special output filename "-" or ">&STDOUT" is given
1143 then the STDOUT filehandle is used for output (and no open or close is
1144 performed). If the special output filename ">&STDERR" is given then the
1145 STDERR filehandle is used for output (and no open or close is
1146 performed). If no output filehandle is currently in use and no output
1147 filename is specified, then "-" is implied.
1148 Alternatively, an L<IO::String> object is also accepted as an output
1151 This method does I<not> usually need to be overridden by subclasses.
1155 sub parse_from_file {
1157 my %opts = (ref $_[0] eq 'HASH') ? %{ shift() } : ();
1158 my ($infile, $outfile) = @_;
1159 my ($in_fh, $out_fh);
1161 ($in_fh, $out_fh) = (gensym(), gensym());
1163 my ($close_input, $close_output) = (0, 0);
1164 local *myData = $self;
1167 ## Is $infile a filename or a (possibly implied) filehandle
1168 if (defined $infile && ref $infile) {
1169 if (ref($infile) =~ /^(SCALAR|ARRAY|HASH|CODE|REF)$/) {
1170 croak "Input from $1 reference not supported!\n";
1172 ## Must be a filehandle-ref (or else assume its a ref to an object
1173 ## that supports the common IO read operations).
1174 $myData{_INFILE} = ${$infile};
1177 elsif (!defined($infile) || !length($infile) || ($infile eq '-')
1178 || ($infile =~ /^<&(?:STDIN|0)$/i))
1180 ## Not a filename, just a string implying STDIN
1182 $myData{_INFILE} = "<standard input>";
1186 ## We have a filename, open it for reading
1187 $myData{_INFILE} = $infile;
1188 open($in_fh, "< $infile") or
1189 croak "Can't open $infile for reading: $!\n";
1193 ## NOTE: we need to be *very* careful when "defaulting" the output
1194 ## file. We only want to use a default if this is the beginning of
1195 ## the entire document (but *not* if this is an included file). We
1196 ## determine this by seeing if the input stream stack has been set-up
1199 ## Is $outfile a filename, a (possibly implied) filehandle, maybe a ref?
1201 ## we need to check for ref() first, as other checks involve reading
1202 if (ref($outfile) =~ /^(ARRAY|HASH|CODE)$/) {
1203 croak "Output to $1 reference not supported!\n";
1205 elsif (ref($outfile) eq 'SCALAR') {
1206 # # NOTE: IO::String isn't a part of the perl distribution,
1207 # # so probably we shouldn't support this case...
1208 # require IO::String;
1209 # $myData{_OUTFILE} = "$outfile";
1210 # $out_fh = IO::String->new($outfile);
1211 croak "Output to SCALAR reference not supported!\n";
1214 ## Must be a filehandle-ref (or else assume its a ref to an
1215 ## object that supports the common IO write operations).
1216 $myData{_OUTFILE} = ${$outfile};
1220 elsif (!defined($outfile) || !length($outfile) || ($outfile eq '-')
1221 || ($outfile =~ /^>&?(?:STDOUT|1)$/i))
1223 if (defined $myData{_TOP_STREAM}) {
1224 $out_fh = $myData{_OUTPUT};
1227 ## Not a filename, just a string implying STDOUT
1229 $myData{_OUTFILE} = "<standard output>";
1233 elsif ($outfile =~ /^>&(STDERR|2)$/i) {
1234 ## Not a filename, just a string implying STDERR
1235 $myData{_OUTFILE} = "<standard error>";
1239 ## We have a filename, open it for writing
1240 $myData{_OUTFILE} = $outfile;
1241 (-d $outfile) and croak "$outfile is a directory, not POD input!\n";
1242 open($out_fh, "> $outfile") or
1243 croak "Can't open $outfile for writing: $!\n";
1247 ## Whew! That was a lot of work to set up reasonably/robust behavior
1248 ## in the case of a non-filename for reading and writing. Now we just
1249 ## have to parse the input and close the handles when we're finished.
1250 $self->parse_from_filehandle(\%opts, $in_fh, $out_fh);
1253 close($in_fh) || croak "Can't close $infile after reading: $!\n";
1255 close($out_fh) || croak "Can't close $outfile after writing: $!\n";
1258 #############################################################################
1260 =head1 ACCESSOR METHODS
1262 Clients of B<Pod::Parser> should use the following methods to access
1263 instance data fields:
1267 ##---------------------------------------------------------------------------
1269 =head1 B<errorsub()>
1271 $parser->errorsub("method_name");
1272 $parser->errorsub(\&warn_user);
1273 $parser->errorsub(sub { print STDERR, @_ });
1275 Specifies the method or subroutine to use when printing error messages
1276 about POD syntax. The supplied method/subroutine I<must> return TRUE upon
1277 successful printing of the message. If C<undef> is given, then the B<warn>
1278 builtin is used to issue error messages (this is the default behavior).
1280 my $errorsub = $parser->errorsub()
1281 my $errmsg = "This is an error message!\n"
1282 (ref $errorsub) and &{$errorsub}($errmsg)
1283 or (defined $errorsub) and $parser->$errorsub($errmsg)
1286 Returns a method name, or else a reference to the user-supplied subroutine
1287 used to print error messages. Returns C<undef> if the B<warn> builtin
1288 is used to issue error messages (this is the default behavior).
1293 return (@_ > 1) ? ($_[0]->{_ERRORSUB} = $_[1]) : $_[0]->{_ERRORSUB};
1296 ##---------------------------------------------------------------------------
1300 $boolean = $parser->cutting();
1302 Returns the current C<cutting> state: a boolean-valued scalar which
1303 evaluates to true if text from the input file is currently being "cut"
1304 (meaning it is I<not> considered part of the POD document).
1306 $parser->cutting($boolean);
1308 Sets the current C<cutting> state to the given value and returns the
1314 return (@_ > 1) ? ($_[0]->{_CUTTING} = $_[1]) : $_[0]->{_CUTTING};
1317 ##---------------------------------------------------------------------------
1319 ##---------------------------------------------------------------------------
1321 =head1 B<parseopts()>
1323 When invoked with no additional arguments, B<parseopts> returns a hashtable
1324 of all the current parsing options.
1326 ## See if we are parsing non-POD sections as well as POD ones
1327 my %opts = $parser->parseopts();
1328 $opts{'-want_nonPODs}' and print "-want_nonPODs\n";
1330 When invoked using a single string, B<parseopts> treats the string as the
1331 name of a parse-option and returns its corresponding value if it exists
1332 (returns C<undef> if it doesn't).
1334 ## Did we ask to see '=cut' paragraphs?
1335 my $want_cut = $parser->parseopts('-process_cut_cmd');
1336 $want_cut and print "-process_cut_cmd\n";
1338 When invoked with multiple arguments, B<parseopts> treats them as
1339 key/value pairs and the specified parse-option names are set to the
1340 given values. Any unspecified parse-options are unaffected.
1342 ## Set them back to the default
1343 $parser->parseopts(-warnings => 0);
1345 When passed a single hash-ref, B<parseopts> uses that hash to completely
1346 reset the existing parse-options, all previous parse-option values
1349 ## Reset all options to default
1350 $parser->parseopts( { } );
1352 See L<"PARSING OPTIONS"> for more information on the name and meaning of each
1353 parse-option currently recognized.
1358 local *myData = shift;
1359 local *myOpts = ($myData{_PARSEOPTS} ||= {});
1360 return %myOpts if (@_ == 0);
1363 return ref($_) ? $myData{_PARSEOPTS} = $_ : $myOpts{$_};
1365 my @newOpts = (%myOpts, @_);
1366 $myData{_PARSEOPTS} = { @newOpts };
1369 ##---------------------------------------------------------------------------
1371 =head1 B<output_file()>
1373 $fname = $parser->output_file();
1375 Returns the name of the output file being written.
1380 return $_[0]->{_OUTFILE};
1383 ##---------------------------------------------------------------------------
1385 =head1 B<output_handle()>
1387 $fhandle = $parser->output_handle();
1389 Returns the output filehandle object.
1394 return $_[0]->{_OUTPUT};
1397 ##---------------------------------------------------------------------------
1399 =head1 B<input_file()>
1401 $fname = $parser->input_file();
1403 Returns the name of the input file being read.
1408 return $_[0]->{_INFILE};
1411 ##---------------------------------------------------------------------------
1413 =head1 B<input_handle()>
1415 $fhandle = $parser->input_handle();
1417 Returns the current input filehandle object.
1422 return $_[0]->{_INPUT};
1425 ##---------------------------------------------------------------------------
1429 =head1 B<input_streams()>
1431 $listref = $parser->input_streams();
1433 Returns a reference to an array which corresponds to the stack of all
1434 the input streams that are currently in the middle of being parsed.
1436 While parsing an input stream, it is possible to invoke
1437 B<parse_from_file()> or B<parse_from_filehandle()> to parse a new input
1438 stream and then return to parsing the previous input stream. Each input
1439 stream to be parsed is pushed onto the end of this input stack
1440 before any of its input is read. The input stream that is currently
1441 being parsed is always at the end (or top) of the input stack. When an
1442 input stream has been exhausted, it is popped off the end of the
1445 Each element on this input stack is a reference to C<Pod::InputSource>
1446 object. Please see L<Pod::InputObjects> for more details.
1448 This method might be invoked when printing diagnostic messages, for example,
1449 to obtain the name and line number of the all input files that are currently
1457 return $_[0]->{_INPUT_STREAMS};
1460 ##---------------------------------------------------------------------------
1464 =head1 B<top_stream()>
1466 $hashref = $parser->top_stream();
1468 Returns a reference to the hash-table that represents the element
1469 that is currently at the top (end) of the input stream stack
1470 (see L<"input_streams()">). The return value will be the C<undef>
1471 if the input stack is empty.
1473 This method might be used when printing diagnostic messages, for example,
1474 to obtain the name and line number of the current input file.
1481 return $_[0]->{_TOP_STREAM} || undef;
1484 #############################################################################
1486 =head1 PRIVATE METHODS AND DATA
1488 B<Pod::Parser> makes use of several internal methods and data fields
1489 which clients should not need to see or use. For the sake of avoiding
1490 name collisions for client data and methods, these methods and fields
1491 are briefly discussed here. Determined hackers may obtain further
1492 information about them by reading the B<Pod::Parser> source code.
1494 Private data fields are stored in the hash-object whose reference is
1495 returned by the B<new()> constructor for this class. The names of all
1496 private methods and data-fields used by B<Pod::Parser> begin with a
1497 prefix of "_" and match the regular expression C</^_\w+$/>.
1501 ##---------------------------------------------------------------------------
1505 =head1 B<_push_input_stream()>
1507 $hashref = $parser->_push_input_stream($in_fh,$out_fh);
1509 This method will push the given input stream on the input stack and
1510 perform any necessary beginning-of-document or beginning-of-file
1511 processing. The argument C<$in_fh> is the input stream filehandle to
1512 push, and C<$out_fh> is the corresponding output filehandle to use (if
1513 it is not given or is undefined, then the current output stream is used,
1514 which defaults to standard output if it doesnt exist yet).
1516 The value returned will be reference to the hash-table that represents
1517 the new top of the input stream stack. I<Please Note> that it is
1518 possible for this method to use default values for the input and output
1519 file handles. If this happens, you will need to look at the C<INPUT>
1520 and C<OUTPUT> instance data members to determine their new values.
1526 sub _push_input_stream {
1527 my ($self, $in_fh, $out_fh) = @_;
1528 local *myData = $self;
1530 ## Initialize stuff for the entire document if this is *not*
1531 ## an included file.
1533 ## NOTE: we need to be *very* careful when "defaulting" the output
1534 ## filehandle. We only want to use a default value if this is the
1535 ## beginning of the entire document (but *not* if this is an included
1537 unless (defined $myData{_TOP_STREAM}) {
1538 $out_fh = \*STDOUT unless (defined $out_fh);
1539 $myData{_CUTTING} = 1; ## current "cutting" state
1540 $myData{_INPUT_STREAMS} = []; ## stack of all input streams
1543 ## Initialize input indicators
1544 $myData{_OUTFILE} = '(unknown)' unless (defined $myData{_OUTFILE});
1545 $myData{_OUTPUT} = $out_fh if (defined $out_fh);
1546 $in_fh = \*STDIN unless (defined $in_fh);
1547 $myData{_INFILE} = '(unknown)' unless (defined $myData{_INFILE});
1548 $myData{_INPUT} = $in_fh;
1549 my $input_top = $myData{_TOP_STREAM}
1550 = new Pod::InputSource(
1551 -name => $myData{_INFILE},
1553 -was_cutting => $myData{_CUTTING}
1555 local *input_stack = $myData{_INPUT_STREAMS};
1556 push(@input_stack, $input_top);
1558 ## Perform beginning-of-document and/or beginning-of-input processing
1559 $self->begin_pod() if (@input_stack == 1);
1560 $self->begin_input();
1565 ##---------------------------------------------------------------------------
1569 =head1 B<_pop_input_stream()>
1571 $hashref = $parser->_pop_input_stream();
1573 This takes no arguments. It will perform any necessary end-of-file or
1574 end-of-document processing and then pop the current input stream from
1575 the top of the input stack.
1577 The value returned will be reference to the hash-table that represents
1578 the new top of the input stream stack.
1584 sub _pop_input_stream {
1586 local *myData = $self;
1587 local *input_stack = $myData{_INPUT_STREAMS};
1589 ## Perform end-of-input and/or end-of-document processing
1590 $self->end_input() if (@input_stack > 0);
1591 $self->end_pod() if (@input_stack == 1);
1593 ## Restore cutting state to whatever it was before we started
1594 ## parsing this file.
1595 my $old_top = pop(@input_stack);
1596 $myData{_CUTTING} = $old_top->was_cutting();
1598 ## Dont forget to reset the input indicators
1599 my $input_top = undef;
1600 if (@input_stack > 0) {
1601 $input_top = $myData{_TOP_STREAM} = $input_stack[-1];
1602 $myData{_INFILE} = $input_top->name();
1603 $myData{_INPUT} = $input_top->handle();
1605 delete $myData{_TOP_STREAM};
1606 delete $myData{_INPUT_STREAMS};
1612 #############################################################################
1614 =head1 TREE-BASED PARSING
1616 If straightforward stream-based parsing wont meet your needs (as is
1617 likely the case for tasks such as translating PODs into structured
1618 markup languages like HTML and XML) then you may need to take the
1619 tree-based approach. Rather than doing everything in one pass and
1620 calling the B<interpolate()> method to expand sequences into text, it
1621 may be desirable to instead create a parse-tree using the B<parse_text()>
1622 method to return a tree-like structure which may contain an ordered
1623 list of children (each of which may be a text-string, or a similar
1624 tree-like structure).
1626 Pay special attention to L<"METHODS FOR PARSING AND PROCESSING"> and
1627 to the objects described in L<Pod::InputObjects>. The former describes
1628 the gory details and parameters for how to customize and extend the
1629 parsing behavior of B<Pod::Parser>. B<Pod::InputObjects> provides
1630 several objects that may all be used interchangeably as parse-trees. The
1631 most obvious one is the B<Pod::ParseTree> object. It defines the basic
1632 interface and functionality that all things trying to be a POD parse-tree
1633 should do. A B<Pod::ParseTree> is defined such that each "node" may be a
1634 text-string, or a reference to another parse-tree. Each B<Pod::Paragraph>
1635 object and each B<Pod::InteriorSequence> object also supports the basic
1636 parse-tree interface.
1638 The B<parse_text()> method takes a given paragraph of text, and
1639 returns a parse-tree that contains one or more children, each of which
1640 may be a text-string, or an InteriorSequence object. There are also
1641 callback-options that may be passed to B<parse_text()> to customize
1642 the way it expands or transforms interior-sequences, as well as the
1643 returned result. These callbacks can be used to create a parse-tree
1644 with custom-made objects (which may or may not support the parse-tree
1645 interface, depending on how you choose to do it).
1647 If you wish to turn an entire POD document into a parse-tree, that process
1648 is fairly straightforward. The B<parse_text()> method is the key to doing
1649 this successfully. Every paragraph-callback (i.e. the polymorphic methods
1650 for B<command()>, B<verbatim()>, and B<textblock()> paragraphs) takes
1651 a B<Pod::Paragraph> object as an argument. Each paragraph object has a
1652 B<parse_tree()> method that can be used to get or set a corresponding
1653 parse-tree. So for each of those paragraph-callback methods, simply call
1654 B<parse_text()> with the options you desire, and then use the returned
1655 parse-tree to assign to the given paragraph object.
1657 That gives you a parse-tree for each paragraph - so now all you need is
1658 an ordered list of paragraphs. You can maintain that yourself as a data
1659 element in the object/hash. The most straightforward way would be simply
1660 to use an array-ref, with the desired set of custom "options" for each
1661 invocation of B<parse_text>. Let's assume the desired option-set is
1662 given by the hash C<%options>. Then we might do something like the
1665 package MyPodParserTree;
1667 @ISA = qw( Pod::Parser );
1673 $self->{'-paragraphs'} = []; ## initialize paragraph list
1677 my ($parser, $command, $paragraph, $line_num, $pod_para) = @_;
1678 my $ptree = $parser->parse_text({%options}, $paragraph, ...);
1679 $pod_para->parse_tree( $ptree );
1680 push @{ $self->{'-paragraphs'} }, $pod_para;
1684 my ($parser, $paragraph, $line_num, $pod_para) = @_;
1685 push @{ $self->{'-paragraphs'} }, $pod_para;
1689 my ($parser, $paragraph, $line_num, $pod_para) = @_;
1690 my $ptree = $parser->parse_text({%options}, $paragraph, ...);
1691 $pod_para->parse_tree( $ptree );
1692 push @{ $self->{'-paragraphs'} }, $pod_para;
1699 my $parser = new MyPodParserTree(...);
1700 $parser->parse_from_file(...);
1701 my $paragraphs_ref = $parser->{'-paragraphs'};
1703 Of course, in this module-author's humble opinion, I'd be more inclined to
1704 use the existing B<Pod::ParseTree> object than a simple array. That way
1705 everything in it, paragraphs and sequences, all respond to the same core
1706 interface for all parse-tree nodes. The result would look something like:
1708 package MyPodParserTree2;
1714 $self->{'-ptree'} = new Pod::ParseTree; ## initialize parse-tree
1718 ## convenience method to get/set the parse-tree for the entire POD
1719 (@_ > 1) and $_[0]->{'-ptree'} = $_[1];
1720 return $_[0]->{'-ptree'};
1724 my ($parser, $command, $paragraph, $line_num, $pod_para) = @_;
1725 my $ptree = $parser->parse_text({<<options>>}, $paragraph, ...);
1726 $pod_para->parse_tree( $ptree );
1727 $parser->parse_tree()->append( $pod_para );
1731 my ($parser, $paragraph, $line_num, $pod_para) = @_;
1732 $parser->parse_tree()->append( $pod_para );
1736 my ($parser, $paragraph, $line_num, $pod_para) = @_;
1737 my $ptree = $parser->parse_text({<<options>>}, $paragraph, ...);
1738 $pod_para->parse_tree( $ptree );
1739 $parser->parse_tree()->append( $pod_para );
1746 my $parser = new MyPodParserTree2(...);
1747 $parser->parse_from_file(...);
1748 my $ptree = $parser->parse_tree;
1751 Now you have the entire POD document as one great big parse-tree. You
1752 can even use the B<-expand_seq> option to B<parse_text> to insert
1753 whole different kinds of objects. Just don't expect B<Pod::Parser>
1754 to know what to do with them after that. That will need to be in your
1755 code. Or, alternatively, you can insert any object you like so long as
1756 it conforms to the B<Pod::ParseTree> interface.
1758 One could use this to create subclasses of B<Pod::Paragraphs> and
1759 B<Pod::InteriorSequences> for specific commands (or to create your own
1760 custom node-types in the parse-tree) and add some kind of B<emit()>
1761 method to each custom node/subclass object in the tree. Then all you'd
1762 need to do is recursively walk the tree in the desired order, processing
1763 the children (most likely from left to right) by formatting them if
1764 they are text-strings, or by calling their B<emit()> method if they
1765 are objects/references.
1769 Please note that POD has the notion of "paragraphs": this is something
1770 starting I<after> a blank (read: empty) line, with the single exception
1771 of the file start, which is also starting a paragraph. That means that
1772 especially a command (e.g. C<=head1>) I<must> be preceded with a blank
1773 line; C<__END__> is I<not> a blank line.
1777 L<Pod::InputObjects>, L<Pod::Select>
1779 B<Pod::InputObjects> defines POD input objects corresponding to
1780 command paragraphs, parse-trees, and interior-sequences.
1782 B<Pod::Select> is a subclass of B<Pod::Parser> which provides the ability
1783 to selectively include and/or exclude sections of a POD document from being
1784 translated based upon the current heading, subheading, subsubheading, etc.
1787 B<Pod::Callbacks> is a subclass of B<Pod::Parser> which gives its users
1788 the ability the employ I<callback functions> instead of, or in addition
1789 to, overriding methods of the base class.
1792 B<Pod::Select> and B<Pod::Callbacks> do not override any
1793 methods nor do they define any new methods with the same name. Because
1794 of this, they may I<both> be used (in combination) as a base class of
1795 the same subclass in order to combine their functionality without
1796 causing any namespace clashes due to multiple inheritance.
1800 Please report bugs using L<http://rt.cpan.org>.
1802 Brad Appleton E<lt>bradapp@enteract.comE<gt>
1804 Based on code for B<Pod::Text> written by
1805 Tom Christiansen E<lt>tchrist@mox.perl.comE<gt>