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#############################################################################

# Pod/Parser.pm -- package which defines a base class for parsing POD docs.

#

# Copyright (C) 1996-2000 by Bradford Appleton. All rights reserved.

# This file is part of "PodParser". PodParser is free software;

# you can redistribute it and/or modify it under the same terms

# as Perl itself.

#############################################################################

package Pod::Parser;

use strict;

## These "variables" are used as local "glob aliases" for performance

use vars qw($VERSION @ISA %myData %myOpts @input_stack);

use JatsError;

$VERSION = '1.37';  ## Current version of this package

require  5.005;    ## requires this Perl version or later

#############################################################################

=head1 NAME

Pod::Parser - base class for creating POD filters and translators

=head1 SYNOPSIS

    use Pod::Parser;

    package MyParser;

    @ISA = qw(Pod::Parser);

    sub command { 

        my ($parser, $command, $paragraph, $line_num) = @_;

        ## Interpret the command and its text; sample actions might be:

        if ($command eq 'head1') { ... }

        elsif ($command eq 'head2') { ... }

        ## ... other commands and their actions

        my $out_fh = $parser->output_handle();

        my $expansion = $parser->interpolate($paragraph, $line_num);

        print $out_fh $expansion;

    }

    sub verbatim { 

        my ($parser, $paragraph, $line_num) = @_;

        ## Format verbatim paragraph; sample actions might be:

        my $out_fh = $parser->output_handle();

        print $out_fh $paragraph;

    }

    sub textblock { 

        my ($parser, $paragraph, $line_num) = @_;

        ## Translate/Format this block of text; sample actions might be:

        my $out_fh = $parser->output_handle();

        my $expansion = $parser->interpolate($paragraph, $line_num);

        print $out_fh $expansion;

    }

    sub interior_sequence { 

        my ($parser, $seq_command, $seq_argument) = @_;

        ## Expand an interior sequence; sample actions might be:

        return "*$seq_argument*"     if ($seq_command eq 'B');

        return "`$seq_argument'"     if ($seq_command eq 'C');

        return "_${seq_argument}_'"  if ($seq_command eq 'I');

        ## ... other sequence commands and their resulting text

    }

    package main;

    ## Create a parser object and have it parse file whose name was

    ## given on the command-line (use STDIN if no files were given).

    $parser = new MyParser();

    $parser->parse_from_filehandle(\*STDIN)  if (@ARGV == 0);

    for (@ARGV) { $parser->parse_from_file($_); }

=head1 REQUIRES

perl5.005, Pod::InputObjects, Exporter, Symbol, Carp

=head1 EXPORTS

Nothing.

=head1 DESCRIPTION

B<Pod::Parser> is a base class for creating POD filters and translators.

It handles most of the effort involved with parsing the POD sections

from an input stream, leaving subclasses free to be concerned only with

performing the actual translation of text.

B<Pod::Parser> parses PODs, and makes method calls to handle the various

components of the POD. Subclasses of B<Pod::Parser> override these methods

to translate the POD into whatever output format they desire.

=head1 QUICK OVERVIEW

To create a POD filter for translating POD documentation into some other

format, you create a subclass of B<Pod::Parser> which typically overrides

just the base class implementation for the following methods:

=over 2

=item *

B<command()>

=item *

B<verbatim()>

=item *

B<textblock()>

=item *

B<interior_sequence()>

=back

You may also want to override the B<begin_input()> and B<end_input()>

methods for your subclass (to perform any needed per-file and/or

per-document initialization or cleanup).

If you need to perform any preprocessing of input before it is parsed

you may want to override one or more of B<preprocess_line()> and/or

B<preprocess_paragraph()>.

Sometimes it may be necessary to make more than one pass over the input

files. If this is the case you have several options. You can make the

first pass using B<Pod::Parser> and override your methods to store the

intermediate results in memory somewhere for the B<end_pod()> method to

process. You could use B<Pod::Parser> for several passes with an

appropriate state variable to control the operation for each pass. If

your input source can't be reset to start at the beginning, you can

store it in some other structure as a string or an array and have that

structure implement a B<getline()> method (which is all that

B<parse_from_filehandle()> uses to read input).

Feel free to add any member data fields you need to keep track of things

like current font, indentation, horizontal or vertical position, or

whatever else you like. Be sure to read L<"PRIVATE METHODS AND DATA">

to avoid name collisions.

For the most part, the B<Pod::Parser> base class should be able to

do most of the input parsing for you and leave you free to worry about

how to interpret the commands and translate the result.

Note that all we have described here in this quick overview is the

simplest most straightforward use of B<Pod::Parser> to do stream-based

parsing. It is also possible to use the B<Pod::Parser::parse_text> function

to do more sophisticated tree-based parsing. See L<"TREE-BASED PARSING">.

=head1 PARSING OPTIONS

A I<parse-option> is simply a named option of B<Pod::Parser> with a

value that corresponds to a certain specified behavior. These various

behaviors of B<Pod::Parser> may be enabled/disabled by setting

or unsetting one or more I<parse-options> using the B<parseopts()> method.

The set of currently accepted parse-options is as follows:

=over 3

=item B<-want_nonPODs> (default: unset)

Normally (by default) B<Pod::Parser> will only provide access to

the POD sections of the input. Input paragraphs that are not part

of the POD-format documentation are not made available to the caller

(not even using B<preprocess_paragraph()>). Setting this option to a

non-empty, non-zero value will allow B<preprocess_paragraph()> to see

non-POD sections of the input as well as POD sections. The B<cutting()>

method can be used to determine if the corresponding paragraph is a POD

paragraph, or some other input paragraph.

=item B<-process_cut_cmd> (default: unset)

Normally (by default) B<Pod::Parser> handles the C<=cut> POD directive

by itself and does not pass it on to the caller for processing. Setting

this option to a non-empty, non-zero value will cause B<Pod::Parser> to

pass the C<=cut> directive to the caller just like any other POD command

(and hence it may be processed by the B<command()> method).

B<Pod::Parser> will still interpret the C<=cut> directive to mean that

"cutting mode" has been (re)entered, but the caller will get a chance

to capture the actual C<=cut> paragraph itself for whatever purpose

it desires.

=item B<-warnings> (default: unset)

Normally (by default) B<Pod::Parser> recognizes a bare minimum of

pod syntax errors and warnings and issues diagnostic messages

for errors, but not for warnings. (Use B<Pod::Checker> to do more

thorough checking of POD syntax.) Setting this option to a non-empty,

non-zero value will cause B<Pod::Parser> to issue diagnostics for

the few warnings it recognizes as well as the errors.

=back

Please see L<"parseopts()"> for a complete description of the interface

for the setting and unsetting of parse-options.

=cut

#############################################################################

#use diagnostics;

use Pod::InputObjects;

use Carp;

use Exporter;

BEGIN {

   if ($] < 5.006) {

      require Symbol;

      import Symbol;

   }

}

@ISA = qw(Exporter);

#############################################################################

=head1 RECOMMENDED SUBROUTINE/METHOD OVERRIDES

B<Pod::Parser> provides several methods which most subclasses will probably

want to override. These methods are as follows:

=cut

##---------------------------------------------------------------------------

=head1 B<command()>

            $parser->command($cmd,$text,$line_num,$pod_para);

This method should be overridden by subclasses to take the appropriate

action when a POD command paragraph (denoted by a line beginning with

"=") is encountered. When such a POD directive is seen in the input,

this method is called and is passed:

=over 3

=item C<$cmd>

the name of the command for this POD paragraph

=item C<$text>

the paragraph text for the given POD paragraph command.

=item C<$line_num>

the line-number of the beginning of the paragraph

=item C<$pod_para>

a reference to a C<Pod::Paragraph> object which contains further

information about the paragraph command (see L<Pod::InputObjects>

for details).

=back

B<Note> that this method I<is> called for C<=pod> paragraphs.

The base class implementation of this method simply treats the raw POD

command as normal block of paragraph text (invoking the B<textblock()>

method with the command paragraph).

=cut

sub command {

    my ($self, $cmd, $text, $line_num, $pod_para)  = @_;

    ## Just treat this like a textblock

    $self->textblock($pod_para->raw_text(), $line_num, $pod_para);

}

##---------------------------------------------------------------------------

=head1 B<verbatim()>

            $parser->verbatim($text,$line_num,$pod_para);

This method may be overridden by subclasses to take the appropriate

action when a block of verbatim text is encountered. It is passed the

following parameters:

=over 3

=item C<$text>

the block of text for the verbatim paragraph

=item C<$line_num>

the line-number of the beginning of the paragraph

=item C<$pod_para>

a reference to a C<Pod::Paragraph> object which contains further

information about the paragraph (see L<Pod::InputObjects>

for details).

=back

The base class implementation of this method simply prints the textblock

(unmodified) to the output filehandle.

=cut

sub verbatim {

    my ($self, $text, $line_num, $pod_para) = @_;

    my $out_fh = $self->{_OUTPUT};

    print $out_fh $text;

}

##---------------------------------------------------------------------------

=head1 B<textblock()>

            $parser->textblock($text,$line_num,$pod_para);

This method may be overridden by subclasses to take the appropriate

action when a normal block of POD text is encountered (although the base

class method will usually do what you want). It is passed the following

parameters:

=over 3

=item C<$text>

the block of text for the a POD paragraph

=item C<$line_num>

the line-number of the beginning of the paragraph

=item C<$pod_para>

a reference to a C<Pod::Paragraph> object which contains further

information about the paragraph (see L<Pod::InputObjects>

for details).

=back

In order to process interior sequences, subclasses implementations of

this method will probably want to invoke either B<interpolate()> or

B<parse_text()>, passing it the text block C<$text>, and the corresponding

line number in C<$line_num>, and then perform any desired processing upon

the returned result.

The base class implementation of this method simply prints the text block

as it occurred in the input stream).

=cut

sub textblock {

    my ($self, $text, $line_num, $pod_para) = @_;

    my $out_fh = $self->{_OUTPUT};

    print $out_fh $self->interpolate($text, $line_num);

}

##---------------------------------------------------------------------------

=head1 B<interior_sequence()>

            $parser->interior_sequence($seq_cmd,$seq_arg,$pod_seq);

This method should be overridden by subclasses to take the appropriate

action when an interior sequence is encountered. An interior sequence is

an embedded command within a block of text which appears as a command

name (usually a single uppercase character) followed immediately by a

string of text which is enclosed in angle brackets. This method is

passed the sequence command C<$seq_cmd> and the corresponding text

C<$seq_arg>. It is invoked by the B<interpolate()> method for each interior

sequence that occurs in the string that it is passed. It should return

the desired text string to be used in place of the interior sequence.

The C<$pod_seq> argument is a reference to a C<Pod::InteriorSequence>

object which contains further information about the interior sequence.

Please see L<Pod::InputObjects> for details if you need to access this

additional information.

Subclass implementations of this method may wish to invoke the 

B<nested()> method of C<$pod_seq> to see if it is nested inside

some other interior-sequence (and if so, which kind).

The base class implementation of the B<interior_sequence()> method

simply returns the raw text of the interior sequence (as it occurred

in the input) to the caller.

=cut

sub interior_sequence {

    my ($self, $seq_cmd, $seq_arg, $pod_seq) = @_;

    ## Just return the raw text of the interior sequence

    return  $pod_seq->raw_text();

}

#############################################################################

=head1 OPTIONAL SUBROUTINE/METHOD OVERRIDES

B<Pod::Parser> provides several methods which subclasses may want to override

to perform any special pre/post-processing. These methods do I<not> have to

be overridden, but it may be useful for subclasses to take advantage of them.

=cut

##---------------------------------------------------------------------------

=head1 B<new()>

            my $parser = Pod::Parser->new();

This is the constructor for B<Pod::Parser> and its subclasses. You

I<do not> need to override this method! It is capable of constructing

subclass objects as well as base class objects, provided you use

any of the following constructor invocation styles:

    my $parser1 = MyParser->new();

    my $parser2 = new MyParser();

    my $parser3 = $parser2->new();

where C<MyParser> is some subclass of B<Pod::Parser>.

Using the syntax C<MyParser::new()> to invoke the constructor is I<not>

recommended, but if you insist on being able to do this, then the

subclass I<will> need to override the B<new()> constructor method. If

you do override the constructor, you I<must> be sure to invoke the

B<initialize()> method of the newly blessed object.

Using any of the above invocations, the first argument to the

constructor is always the corresponding package name (or object

reference). No other arguments are required, but if desired, an

associative array (or hash-table) my be passed to the B<new()>

constructor, as in:

    my $parser1 = MyParser->new( MYDATA => $value1, MOREDATA => $value2 );

    my $parser2 = new MyParser( -myflag => 1 );

All arguments passed to the B<new()> constructor will be treated as

key/value pairs in a hash-table. The newly constructed object will be

initialized by copying the contents of the given hash-table (which may

have been empty). The B<new()> constructor for this class and all of its

subclasses returns a blessed reference to the initialized object (hash-table).

=cut

sub new {

    ## Determine if we were called via an object-ref or a classname

    my ($this,%params) = @_;

    my $class = ref($this) || $this;

    ## Any remaining arguments are treated as initial values for the

    ## hash that is used to represent this object.

    my $self = { %params };

    ## Bless ourselves into the desired class and perform any initialization

    bless $self, $class;

    $self->initialize();

    return $self;

}

##---------------------------------------------------------------------------

=head1 B<initialize()>

            $parser->initialize();

This method performs any necessary object initialization. It takes no

arguments (other than the object instance of course, which is typically

copied to a local variable named C<$self>). If subclasses override this

method then they I<must> be sure to invoke C<$self-E<gt>SUPER::initialize()>.

=cut

sub initialize {

    #my $self = shift;

    #return;

}

##---------------------------------------------------------------------------

=head1 B<begin_pod()>

            $parser->begin_pod();

This method is invoked at the beginning of processing for each POD

document that is encountered in the input. Subclasses should override

this method to perform any per-document initialization.

=cut

sub begin_pod {

    #my $self = shift;

    #return;

}

##---------------------------------------------------------------------------

=head1 B<begin_input()>

            $parser->begin_input();

This method is invoked by B<parse_from_filehandle()> immediately I<before>

processing input from a filehandle. The base class implementation does

nothing, however, subclasses may override it to perform any per-file

initializations.

Note that if multiple files are parsed for a single POD document

(perhaps the result of some future C<=include> directive) this method

is invoked for every file that is parsed. If you wish to perform certain

initializations once per document, then you should use B<begin_pod()>.

=cut

sub begin_input {

    #my $self = shift;

    #return;

}

##---------------------------------------------------------------------------

=head1 B<end_input()>

            $parser->end_input();

This method is invoked by B<parse_from_filehandle()> immediately I<after>

processing input from a filehandle. The base class implementation does

nothing, however, subclasses may override it to perform any per-file

cleanup actions.

Please note that if multiple files are parsed for a single POD document

(perhaps the result of some kind of C<=include> directive) this method

is invoked for every file that is parsed. If you wish to perform certain

cleanup actions once per document, then you should use B<end_pod()>.

=cut

sub end_input {

    #my $self = shift;

    #return;

}

##---------------------------------------------------------------------------

=head1 B<end_pod()>

            $parser->end_pod();

This method is invoked at the end of processing for each POD document

that is encountered in the input. Subclasses should override this method

to perform any per-document finalization.

=cut

sub end_pod {

    #my $self = shift;

    #return;

}

##---------------------------------------------------------------------------

=head1 B<preprocess_line()>

          $textline = $parser->preprocess_line($text, $line_num);

This method should be overridden by subclasses that wish to perform

any kind of preprocessing for each I<line> of input (I<before> it has

been determined whether or not it is part of a POD paragraph). The

parameter C<$text> is the input line; and the parameter C<$line_num> is

the line number of the corresponding text line.

The value returned should correspond to the new text to use in its

place.  If the empty string or an undefined value is returned then no

further processing will be performed for this line.

Please note that the B<preprocess_line()> method is invoked I<before>

the B<preprocess_paragraph()> method. After all (possibly preprocessed)

lines in a paragraph have been assembled together and it has been

determined that the paragraph is part of the POD documentation from one

of the selected sections, then B<preprocess_paragraph()> is invoked.

The base class implementation of this method returns the given text.

=cut

sub preprocess_line {

    my ($self, $text, $line_num) = @_;

    return  $text;

}

##---------------------------------------------------------------------------

=head1 B<preprocess_paragraph()>

            $textblock = $parser->preprocess_paragraph($text, $line_num);

This method should be overridden by subclasses that wish to perform any

kind of preprocessing for each block (paragraph) of POD documentation

that appears in the input stream. The parameter C<$text> is the POD

paragraph from the input file; and the parameter C<$line_num> is the

line number for the beginning of the corresponding paragraph.

The value returned should correspond to the new text to use in its

place If the empty string is returned or an undefined value is

returned, then the given C<$text> is ignored (not processed).

This method is invoked after gathering up all the lines in a paragraph

and after determining the cutting state of the paragraph,

but before trying to further parse or interpret them. After

B<preprocess_paragraph()> returns, the current cutting state (which

is returned by C<$self-E<gt>cutting()>) is examined. If it evaluates

to true then input text (including the given C<$text>) is cut (not

processed) until the next POD directive is encountered.

Please note that the B<preprocess_line()> method is invoked I<before>

the B<preprocess_paragraph()> method. After all (possibly preprocessed)

lines in a paragraph have been assembled together and either it has been

determined that the paragraph is part of the POD documentation from one

of the selected sections or the C<-want_nonPODs> option is true,

then B<preprocess_paragraph()> is invoked.

The base class implementation of this method returns the given text.

=cut

sub preprocess_paragraph {

    my ($self, $text, $line_num) = @_;

    return  $text;

}

#############################################################################

=head1 METHODS FOR PARSING AND PROCESSING

B<Pod::Parser> provides several methods to process input text. These

methods typically won't need to be overridden (and in some cases they

can't be overridden), but subclasses may want to invoke them to exploit

their functionality.

=cut

##---------------------------------------------------------------------------

=head1 B<parse_text()>

            $ptree1 = $parser->parse_text($text, $line_num);

            $ptree2 = $parser->parse_text({%opts}, $text, $line_num);

            $ptree3 = $parser->parse_text(\%opts, $text, $line_num);

This method is useful if you need to perform your own interpolation 

of interior sequences and can't rely upon B<interpolate> to expand

them in simple bottom-up order.

The parameter C<$text> is a string or block of text to be parsed

for interior sequences; and the parameter C<$line_num> is the

line number corresponding to the beginning of C<$text>.

B<parse_text()> will parse the given text into a parse-tree of "nodes."

and interior-sequences.  Each "node" in the parse tree is either a

text-string, or a B<Pod::InteriorSequence>.  The result returned is a

parse-tree of type B<Pod::ParseTree>. Please see L<Pod::InputObjects>

for more information about B<Pod::InteriorSequence> and B<Pod::ParseTree>.

If desired, an optional hash-ref may be specified as the first argument

to customize certain aspects of the parse-tree that is created and

returned. The set of recognized option keywords are:

=over 3

=item B<-expand_seq> =E<gt> I<code-ref>|I<method-name>

Normally, the parse-tree returned by B<parse_text()> will contain an

unexpanded C<Pod::InteriorSequence> object for each interior-sequence

encountered. Specifying B<-expand_seq> tells B<parse_text()> to "expand"

every interior-sequence it sees by invoking the referenced function

(or named method of the parser object) and using the return value as the

expanded result.

If a subroutine reference was given, it is invoked as:

  &$code_ref( $parser, $sequence )

and if a method-name was given, it is invoked as:

  $parser->method_name( $sequence )

where C<$parser> is a reference to the parser object, and C<$sequence>

is a reference to the interior-sequence object.

[I<NOTE>: If the B<interior_sequence()> method is specified, then it is

invoked according to the interface specified in L<"interior_sequence()">].

=item B<-expand_text> =E<gt> I<code-ref>|I<method-name>

Normally, the parse-tree returned by B<parse_text()> will contain a

text-string for each contiguous sequence of characters outside of an

interior-sequence. Specifying B<-expand_text> tells B<parse_text()> to

"preprocess" every such text-string it sees by invoking the referenced

function (or named method of the parser object) and using the return value

as the preprocessed (or "expanded") result. [Note that if the result is

an interior-sequence, then it will I<not> be expanded as specified by the

B<-expand_seq> option; Any such recursive expansion needs to be handled by

the specified callback routine.]

If a subroutine reference was given, it is invoked as:

  &$code_ref( $parser, $text, $ptree_node )

and if a method-name was given, it is invoked as:

  $parser->method_name( $text, $ptree_node )

where C<$parser> is a reference to the parser object, C<$text> is the

text-string encountered, and C<$ptree_node> is a reference to the current

node in the parse-tree (usually an interior-sequence object or else the

top-level node of the parse-tree).

=item B<-expand_ptree> =E<gt> I<code-ref>|I<method-name>

Rather than returning a C<Pod::ParseTree>, pass the parse-tree as an

argument to the referenced subroutine (or named method of the parser

object) and return the result instead of the parse-tree object.

If a subroutine reference was given, it is invoked as:

  &$code_ref( $parser, $ptree )

and if a method-name was given, it is invoked as:

  $parser->method_name( $ptree )

where C<$parser> is a reference to the parser object, and C<$ptree>

is a reference to the parse-tree object.

=back

=cut

sub parse_text {

    my $self = shift;

    local $_ = '';

    ## Get options and set any defaults

    my %opts = (ref $_[0]) ? %{ shift() } : ();

    my $expand_seq   = $opts{'-expand_seq'}   || undef;

    my $expand_text  = $opts{'-expand_text'}  || undef;

    my $expand_ptree = $opts{'-expand_ptree'} || undef;

    my $text = shift;

    my $line = shift;

    my $file = $self->input_file();

    my $cmd  = "";

    ## Convert method calls into closures, for our convenience

    my $xseq_sub   = $expand_seq;

    my $xtext_sub  = $expand_text;

    my $xptree_sub = $expand_ptree;

    if (defined $expand_seq  and  $expand_seq eq 'interior_sequence') {

        ## If 'interior_sequence' is the method to use, we have to pass

        ## more than just the sequence object, we also need to pass the

        ## sequence name and text.

        $xseq_sub = sub {

            my ($sself, $iseq) = @_;

            my $args = join('', $iseq->parse_tree->children);

            return  $sself->interior_sequence($iseq->name, $args, $iseq);

        };

    }

    ref $xseq_sub    or  $xseq_sub   = sub { shift()->$expand_seq(@_) };

    ref $xtext_sub   or  $xtext_sub  = sub { shift()->$expand_text(@_) };

    ref $xptree_sub  or  $xptree_sub = sub { shift()->$expand_ptree(@_) };

    ## Keep track of the "current" interior sequence, and maintain a stack

    ## of "in progress" sequences.

    ##

    ## NOTE that we push our own "accumulator" at the very beginning of the

    ## stack. It's really a parse-tree, not a sequence; but it implements

    ## the methods we need so we can use it to gather-up all the sequences

    ## and strings we parse. Thus, by the end of our parsing, it should be

    ## the only thing left on our stack and all we have to do is return it!

    ##

    my $seq       = Pod::ParseTree->new();

    my @seq_stack = ($seq);

    my ($ldelim, $rdelim) = ('', '');

    ## Iterate over all sequence starts text (NOTE: split with

    ## capturing parens keeps the delimiters)

    $_ = $text;

    my @tokens = split /([A-Z]<(?:<+\s)?)/;

    while ( @tokens ) {

        $_ = shift @tokens;

        ## Look for the beginning of a sequence

        if ( /^([A-Z])(<(?:<+\s)?)$/ ) {

            ## Push a new sequence onto the stack of those "in-progress"

            my $ldelim_orig;

            ($cmd, $ldelim_orig) = ($1, $2);

            ($ldelim = $ldelim_orig) =~ s/\s+$//;

            ($rdelim = $ldelim) =~ tr/</>/;

            $seq = Pod::InteriorSequence->new(

                       -name   => $cmd,

                       -ldelim => $ldelim_orig,  -rdelim => $rdelim,

                       -file   => $file,    -line   => $line

                   );

            (@seq_stack > 1)  and  $seq->nested($seq_stack[-1]);

            push @seq_stack, $seq;

        }

        ## Look for sequence ending

        elsif ( @seq_stack > 1 ) {

            ## Make sure we match the right kind of closing delimiter

            my ($seq_end, $post_seq) = ('', '');

            if ( ($ldelim eq '<'   and  /\A(.*?)(>)/s)

                 or  /\A(.*?)(\s+$rdelim)/s )

            {

                ## Found end-of-sequence, capture the interior and the

                ## closing the delimiter, and put the rest back on the

                ## token-list

                $post_seq = substr($_, length($1) + length($2));

                ($_, $seq_end) = ($1, $2);

                (length $post_seq)  and  unshift @tokens, $post_seq;

            }

            if (length) {

                ## In the middle of a sequence, append this text to it, and

                ## dont forget to "expand" it if that's what the caller wanted

                $seq->append($expand_text ? &$xtext_sub($self,$_,$seq) : $_);

                $_ .= $seq_end;

            }

            if (length $seq_end) {

                ## End of current sequence, record terminating delimiter

                $seq->rdelim($seq_end);

                ## Pop it off the stack of "in progress" sequences

                pop @seq_stack;

                ## Append result to its parent in current parse tree

                $seq_stack[-1]->append($expand_seq ? &$xseq_sub($self,$seq)

                                                   : $seq);

                ## Remember the current cmd-name and left-delimiter

                if(@seq_stack > 1) {

                    $cmd = $seq_stack[-1]->name;

                    $ldelim = $seq_stack[-1]->ldelim;

                    $rdelim = $seq_stack[-1]->rdelim;

                } else {

                    $cmd = $ldelim = $rdelim = '';

                }

            }

        }

        elsif (length) {

            ## In the middle of a sequence, append this text to it, and

            ## dont forget to "expand" it if that's what the caller wanted

            $seq->append($expand_text ? &$xtext_sub($self,$_,$seq) : $_);

        }

        ## Keep track of line count

        $line += s/\r*\n//;

        ## Remember the "current" sequence

        $seq = $seq_stack[-1];

    }

    ## Handle unterminated sequences

    my $errorsub = (@seq_stack > 1) ? $self->errorsub() : undef;

    while (@seq_stack > 1) {

       ($cmd, $file, $line) = ($seq->name, $seq->file_line);

       $ldelim  = $seq->ldelim;

       ($rdelim = $ldelim) =~ tr/</>/;

       $rdelim  =~ s/^(\S+)(\s*)$/$2$1/;

       pop @seq_stack;

       my $errmsg = "*** ERROR: unterminated ${cmd}${ldelim}...${rdelim}".

                    " at line $line in file $file\n";

       (ref $errorsub) and &{$errorsub}($errmsg)

           or (defined $errorsub) and $self->$errorsub($errmsg)

               or  carp($errmsg);

       $seq_stack[-1]->append($expand_seq ? &$xseq_sub($self,$seq) : $seq);

       $seq = $seq_stack[-1];

    }

    ## Return the resulting parse-tree

    my $ptree = (pop @seq_stack)->parse_tree;

    return  $expand_ptree ? &$xptree_sub($self, $ptree) : $ptree;

}

##---------------------------------------------------------------------------

=head1 B<interpolate()>

            $textblock = $parser->interpolate($text, $line_num);

This method translates all text (including any embedded interior sequences)

in the given text string C<$text> and returns the interpolated result. The

parameter C<$line_num> is the line number corresponding to the beginning

of C<$text>.

B<interpolate()> merely invokes a private method to recursively expand

nested interior sequences in bottom-up order (innermost sequences are

expanded first). If there is a need to expand nested sequences in

some alternate order, use B<parse_text> instead.

=cut

sub interpolate {

    my($self, $text, $line_num) = @_;

    my %parse_opts = ( -expand_seq => 'interior_sequence' );

    my $ptree = $self->parse_text( \%parse_opts, $text, $line_num );

    return  join '', $ptree->children();

}

##---------------------------------------------------------------------------

=begin __PRIVATE__

=head1 B<parse_paragraph()>

            $parser->parse_paragraph($text, $line_num);

This method takes the text of a POD paragraph to be processed, along

with its corresponding line number, and invokes the appropriate method

(one of B<command()>, B<verbatim()>, or B<textblock()>).

For performance reasons, this method is invoked directly without any

dynamic lookup; Hence subclasses may I<not> override it!

=end __PRIVATE__

=cut

sub parse_paragraph {

    my ($self, $text, $line_num) = @_;

    local *myData = $self;  ## alias to avoid deref-ing overhead

    local *myOpts = ($myData{_PARSEOPTS} ||= {});  ## get parse-options

    local $_;

    ## See if we want to preprocess nonPOD paragraphs as well as POD ones.

    my $wantNonPods = $myOpts{'-want_nonPODs'};

    ## Update cutting status

    $myData{_CUTTING} = 0 if $text =~ /^={1,2}\S/;

    ## Perform any desired preprocessing if we wanted it this early

    $wantNonPods  and  $text = $self->preprocess_paragraph($text, $line_num);

    ## Ignore up until next POD directive if we are cutting

    return if $myData{_CUTTING};

    ## Now we know this is block of text in a POD section!

    ##-----------------------------------------------------------------

    ## This is a hook (hack ;-) for Pod::Select to do its thing without

    ## having to override methods, but also without Pod::Parser assuming

    ## $self is an instance of Pod::Select (if the _SELECTED_SECTIONS

    ## field exists then we assume there is an is_selected() method for

    ## us to invoke (calling $self->can('is_selected') could verify this

    ## but that is more overhead than I want to incur)

    ##-----------------------------------------------------------------

    ## Ignore this block if it isnt in one of the selected sections

    if (exists $myData{_SELECTED_SECTIONS}) {

        $self->is_selected($text)  or  return ($myData{_CUTTING} = 1);

    }

    ## If we havent already, perform any desired preprocessing and

    ## then re-check the "cutting" state

    unless ($wantNonPods) {

       $text = $self->preprocess_paragraph($text, $line_num);

       return 1  unless ((defined $text) and (length $text));

       return 1  if ($myData{_CUTTING});

    }

    ## Look for one of the three types of paragraphs

    my ($pfx, $cmd, $arg, $sep) = ('', '', '', '');

    my $pod_para = undef;

    if ($text =~ /^(={1,2})(?=\S)/) {

        ## Looks like a command paragraph. Capture the command prefix used

        ## ("=" or "=="), as well as the command-name, its paragraph text,

        ## and whatever sequence of characters was used to separate them

        $pfx = $1;

        $_ = substr($text, length $pfx);

        ($cmd, $sep, $text) = split /(\s+)/, $_, 2;

        ## If this is a "cut" directive then we dont need to do anything

        ## except return to "cutting" mode.

        if ($cmd eq 'cut') {

           $myData{_CUTTING} = 1;

           return  unless $myOpts{'-process_cut_cmd'};

        }

    }

    ## Save the attributes indicating how the command was specified.

    $pod_para = new Pod::Paragraph(

          -name      => $cmd,

          -text      => $text,

          -prefix    => $pfx,

          -separator => $sep,

          -file      => $myData{_INFILE},

          -line      => $line_num

    );

    # ## Invoke appropriate callbacks

    # if (exists $myData{_CALLBACKS}) {

    #    ## Look through the callback list, invoke callbacks,

    #    ## then see if we need to do the default actions

    #    ## (invoke_callbacks will return true if we do).

    #    return  1  unless $self->invoke_callbacks($cmd, $text, $line_num, $pod_para);

    # }

    # If the last paragraph ended in whitespace, and we're not between verbatim blocks, carp

    if ($myData{_WHITESPACE} and $myOpts{'-warnings'}

            and not ($text =~ /^\s+/ and ($myData{_PREVIOUS}||"") eq "verbatim")) {

        my $errorsub = $self->errorsub();

        my $line = $line_num - 1;

        my $errmsg = "*** WARNING: line containing nothing but whitespace".

                     " in paragraph at line $line in file $myData{_INFILE}\n";

        (ref $errorsub) and &{$errorsub}($errmsg)

            or (defined $errorsub) and $self->$errorsub($errmsg)

                or  carp($errmsg);

    }

    if (length $cmd) {

        ## A command paragraph

        $self->command($cmd, $text, $line_num, $pod_para);

        $myData{_PREVIOUS} = $cmd;

    }

    elsif ($text =~ /^\s+/) {

        ## Indented text - must be a verbatim paragraph

        $self->verbatim($text, $line_num, $pod_para);

        $myData{_PREVIOUS} = "verbatim";

    }

    else {

        ## Looks like an ordinary block of text

        $self->textblock($text, $line_num, $pod_para);

        $myData{_PREVIOUS} = "textblock";

    }

    # Update the whitespace for the next time around