NAME
   LaTeX::TOM - A module for parsing, analyzing, and manipulating LaTeX
   documents.

SYNOPSIS
    use LaTeX::TOM;

    $parser = LaTeX::TOM->new;

    $document = $parser->parseFile('mypaper.tex');

    $latex = $document->toLaTeX;

    $specialnodes = $document->getNodesByCondition(sub {
        my $node = shift;
        return (
          $node->getNodeType eq 'TEXT'
            && $node->getNodeText =~ /magic string/
        );
    });

    $sections = $document->getNodesByCondition(sub {
        my $node = shift;
        return (
          $node->getNodeType eq 'COMMAND'
            && $node->getCommandName =~ /section$/
        );
    });

    $indexme = $document->getIndexableText;

    $document->print;

DESCRIPTION
   This module provides a parser which parses and interprets (though not
   fully) LaTeX documents and returns a tree-based representation of what
   it finds. This tree is a `LaTeX::TOM::Tree'. The tree contains
   `LaTeX::TOM::Node' nodes.

   This module should be especially useful to anyone who wants to do
   processing of LaTeX documents that requires extraction of plain-text
   information, or altering of the plain-text components (or alternatively,
   the math-text components).

COMPONENTS
 LaTeX::TOM::Parser
   The parser recognizes 3 parameters upon creation. The parameters, in
   order, are

   parse error handling (= 0 || 1 || 2)
       Determines what happens when a parse error is encountered. `0'
       results in a warning. `1' results in a die. `2' results in silence.
       Note that particular groupings in LaTeX (i.e. newcommands and the
       like) contain invalid TeX or LaTeX, so you nearly always need this
       parameter to be `0' or `2' to completely parse the document.

   read inputs flag (= 0 || 1)
       This flag determines whether a scan for `\input' and `\input-like'
       commands is performed, and the resulting called files parsed and
       added to the parent parse tree. `0' means no, `1' means do it. Note
       that this will happen recursively if it is turned on. Also,
       bibliographies (.bbl files) are detected and included.

   apply mappings flag (= 0 || 1)
       This flag determines whether (most) user-defined mappings are
       applied. This means `\defs', `\newcommands', and `\newenvironments'.
       This is critical for properly analyzing the content of the document,
       as this must be phrased in terms of the semantics of the original
       TeX and LaTeX commands, not ad hoc user macros. So, for instance, do
       not expect plain-text extraction to work properly with this option
       off.

   The parser returns a `LaTeX::TOM::Tree' ($document in the SYNOPSIS).

 LaTeX::TOM::Node
   Nodes may be of the following types:

   TEXT
       `TEXT' nodes can be thought of as representing the plain-text
       portions of the LaTeX document. This includes math and anything else
       that is not a recognized TeX or LaTeX command, or user-defined
       command. In reality, `TEXT' nodes contain commands that this parser
       does not yet recognize the semantics of.

   COMMAND
       A `COMMAND' node represents a TeX command. It always has child nodes
       in a tree, though the tree might be empty if the command operates on
       zero parameters. An example of a command is

        \textbf{blah}

       This would parse into a `COMMAND' node for `textbf', which would
       have a subtree containing the `TEXT' node with text ``blah.''

   ENVIRONMENT
       Similarly, TeX environments parse into `ENVIRONMENT' nodes, which
       have metadata about the environment, along with a subtree
       representing what is contained in the environment. For example,

        \begin{equation}
          r = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
        \end{equation}

       Would parse into an `ENVIRONMENT' node of the class ``equation''
       with a child tree containing the result of parsing ```r = \frac{-b
       \pm \sqrt{b^2 - 4ac}}{2a}.'''

   GROUP
       A `GROUP' is like an anonymous `COMMAND'. Since you can put whatever
       you want in curly-braces (`{}') in TeX in order to make semantically
       isolated regions, this separation is preserved by the parser. A
       `GROUP' is just the subtree of the parsed contents of plain
       curly-braces.

       It is important to note that currently only the first `GROUP' in a
       series of `GROUP's following a LaTeX command will actually be parsed
       into a `COMMAND' node. The reason is that, for the initial purposes
       of this module, it was not necessary to recognize additional
       `GROUP's as additional parameters to the `COMMAND'. However, this is
       something that this module really should do eventually. Currently if
       you want all the parameters to a multi-parametered command, you'll
       need to pick out all the following `GROUP' nodes yourself.

       Eventually this will become something like a list which is stored in
       the `COMMAND' node, much like XML::DOM's treatment of attributes.
       These are, in a sense, apart from the rest of the document tree.
       Then `GROUP' nodes will become much more rare.

   COMMENT
       A `COMMENT' node is very similar to a `TEXT' node, except it is
       specifically for lines beginning with ```%''' (the TeX comment
       delimeter) or the right-hand portion of a line that has ```%''' at
       some internal point.

 LaTeX::TOM::Trees
   As mentioned before, the Tree is the return result of a parse.

   The tree is nothing more than an arrayref of Nodes, some of which may
   contain their own trees. This is useful knowledge at this point, since
   the user isn't provided with a full suite of convenient
   tree-modification methods. However, Trees do already have some very
   convenient methods, described in the next section.

METHODS
 LaTeX::TOM
   new
       Instantiate a new parser object.

   In this section all of the methods for each of the components are listed
   and described.

 LaTeX::TOM::Parser
   The methods for the parser (aside from the constructor, discussed above)
   are :

   parseFile (filename)
       Read in the contents of *filename* and parse them, returning a
       `LaTeX::TOM::Tree'.

   parse (string)
       Parse the string *string* and return a `LaTeX::TOM::Tree'.

 LaTeX::TOM::Tree
   This section contains methods for the Trees returned by the parser.

   copy
       Duplicate a tree into new memory.

   print
       A debug print of the structure of the tree.

   plainText
       Returns an arrayref which is a list of strings representing the text
       of all `getNodePlainTextFlag = 1' `TEXT' nodes, in an inorder
       traversal.

   indexableText
       A method like the above but which goes one step further; it cleans
       all of the returned text and concatenates it into a single string
       which one could consider having all of the standard information
       retrieval value for the document, making it useful for indexing.

   toLaTeX
       Return a string representing the LaTeX encoded by the tree. This is
       especially useful to get a normal document again, after modifying
       nodes of the tree.

   getTopLevelNodes
       Return a list of `LaTeX::TOM::Nodes' at the top level of the Tree.

   getAllNodes
       Return an arrayref with all nodes of the tree. This "flattens" the
       tree.

   getCommandNodesByName (name)
       Return an arrayref with all `COMMAND' nodes in the tree which have a
       name matching *name*.

   getEnvironmentsByName (name)
       Return an arrayref with all `ENVIRONMENT' nodes in the tree which
       have a class matching *name*.

   getNodesByCondition (code reference)
       This is a catch-all search method which can be used to pull out
       nodes that match pretty much any perl expression, without manually
       having to traverse the tree. *code reference* is a perl code
       reference which receives as its first argument the node of the tree
       that is currently scrutinized and is expected to return a boolean
       value. See the SYNOPSIS for examples.

   getFirstNode
       Returns the first node of the tree. This is useful if you want to
       walk the tree yourself, starting with the first node.

 LaTeX::TOM::Node
   This section contains the methods for nodes of the parsed Trees.

   getNodeType
       Returns the type, one of `TEXT', `COMMAND', `ENVIRONMENT', `GROUP',
       or `COMMENT', as described above.

   getNodeText
       Applicable for `TEXT' or `COMMENT' nodes; this returns the document
       text they contain. This is undef for other node types.

   setNodeText
       Set the node text, also for `TEXT' and `COMMENT' nodes.

   getNodeStartingPosition
       Get the starting character position in the document of this node.
       For `TEXT' and `COMMENT' nodes, this will be where the text begins.
       For `ENVIRONMENT', `COMMAND', or `GROUP' nodes, this will be the
       position of the *last* character of the opening identifier.

   getNodeEndingPosition
       Same as above, but for last character. For `GROUP', `ENVIRONMENT',
       or `COMMAND' nodes, this will be the *first* character of the
       closing identifier.

   getNodeOuterStartingPosition
       Same as getNodeStartingPosition, but for `GROUP', `ENVIRONMENT', or
       `COMMAND' nodes, this returns the *first* character of the opening
       identifier.

   getNodeOuterEndingPosition
       Same as getNodeEndingPosition, but for `GROUP', `ENVIRONMENT', or
       `COMMAND' nodes, this returns the *last* character of the closing
       identifier.

   getNodeMathFlag
       This applies to any node type. It is `1' if the node sets, or is
       contained within, a math mode region. `0' otherwise. `TEXT' nodes
       which have this flag as `1' can be assumed to be the actual
       mathematics contained in the document.

   getNodePlainTextFlag
       This applies only to `TEXT' nodes. It is `1' if the node is non-math
       and is visible (in other words, will end up being a part of the
       output document). One would only want to index `TEXT' nodes with
       this property, for information retrieval purposes.

   getEnvironmentClass
       This applies only to `ENVIRONMENT' nodes. Returns what class of
       environment the node represents (the `X' in `\begin{X}' and
       `\end{X}').

   getCommandName
       This applies only to `COMMAND' nodes. Returns the name of the
       command (the `X' in `\X{...}').

   getChildTree
       This applies only to `COMMAND', `ENVIRONMENT', and `GROUP' nodes: it
       returns the `LaTeX::TOM::Tree' which is ``under'' the calling node.

   getFirstChild
       This applies only to `COMMAND', `ENVIRONMENT', and `GROUP' nodes: it
       returns the first node from the first level of the child subtree.

   getLastChild
       Same as above, but for the last node of the first level.

   getPreviousSibling
       Return the prior node on the same level of the tree.

   getNextSibling
       Same as above, but for following node.

   getParent
       Get the parent node of this node in the tree.

   getNextGroupNode
       This is an interesting function, and kind of a hack because of the
       way the parser makes the current tree. Basically it will give you
       the next sibling that is a `GROUP' node, until it either hits the
       end of the tree level, a `TEXT' node which doesn't match `/^\s*$/',
       or a `COMMAND' node.

       This is useful for finding all `GROUP'ed parameters after a
       `COMMAND' node (see comments for `GROUP' in the `COMPONENTS' /
       `LaTeX::TOM::Node' section). You can just have a while loop that
       calls this method until it gets `undef', and you'll know you've
       found all the parameters to a command.

       Note: this may be bad, but `TEXT' Nodes matching `/^\s*\[[0-9]+\]$/'
       (optional parameter groups) are treated as if they were 'blank'.

CAVEATS
   Due to the lack of tree-modification methods, currently this module is
   mostly useful for minor modifications to the parsed document, for
   instance, altering the text of `TEXT' nodes but not deleting the nodes.
   Of course, the user can still do this by breaking abstraction and
   directly modifying the Tree.

   Also note that the parsing is not complete. This module was not written
   with the intention of being able to produce output documents the way
   ``latex'' does. The intent was instead to be able to analyze and modify
   the document on a logical level with regards to the content; it doesn't
   care about the document formatting and outputting side of TeX/LaTeX.

   There is much work still to be done. See the TODO list in the TOM.pm
   source.

BUGS
   Probably plenty. However, this module has performed fairly well on a set
   of ~1000 research publications from the Computing Research Repository,
   so I deemed it ``good enough'' to use for purposes similar to mine.

   Please let the maintainer know of parser errors if you discover any.

CREDITS
   Thanks to (in order of appearance) who have contributed valuable
   suggestions and patches:

    Otakar Smrz
    Moritz Lenz
    James Bowlin
    Jesse S. Bangs

AUTHORS
   Written by Aaron Krowne <[email protected]>

   Maintained by Steven Schubiger <[email protected]>

LICENSE
   This program is free software; you may redistribute it and/or modify it
   under the same terms as Perl itself.

   See http://dev.perl.org/licenses/

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