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use v5.10;
use warnings;
use Parse::RecDescent;
$RD_TRACE = 1;
my $parser = Parse::RecDescent->new(<<'EOGRAMMAR');
<autotree>
file: element(s)
element: command | literal
command: '\\' literal options(?) args(?)
options: '[' option(s? /,/) ']'
args: '{' element(s?) '}'
option: /[^][\\$&%#_{}~^ \t\n,]+/
literal: /[^][\\$&%#_{}~^ \t\n]+/
EOGRAMMAR
local $/;
my $tree = $parser->file(<DATA>);
$tree->explain(0);
sub file::explain
{
my ($self, $level) = @_;
for (@{$self->{'element(s)'}})
{
$_->explain($level);
print "\n";
}
}
sub element::explain
{
my ($self, $level) = @_;
($self->{command}||$self->{literal})->explain($level)
}
sub command::explain
{
my ($self, $level) = @_;
print "\t"x$level, "Command: $self->{literal}{__VALUE__}\n";
print "\t"x$level, "\tOptions:\n";
$self->{'options(?)'}[0]->explain($level+2) if @{$self->{'options(?)'}};
print "\t"x$level, "\tArgs:\n";
$self->{'args(?)'}[0]->explain($level+2) if @{$self->{'args(?)'}};
}
sub options::explain
{
my ($self, $level) = @_;
$_->explain($level) foreach @{$self->{'option(s?)'}};
}
sub args::explain
{
my ($self, $level) = @_;
$_->explain($level) foreach @{$self->{'element(s?)'}};
}
sub option::explain
{
my ($self, $level) = @_;
print "\t"x$level, "Option: $self->{__VALUE__}\n";
}
sub literal::explain
{
my ($self, $level) = @_;
print "\t"x$level, "Literal: $self->{__VALUE__}\n";
}
__DATA__
\documentclass[a4paper,11pt]{article}
\usepackage{latexsym}
\author{D. Conway}
\title{Parsing \LaTeX{}}
\begin{document}
\maketitle
\tableofcontents
\section{Description}
...is easy \footnote{But not \emph{necessarily} simple}.
\end{document}