NAME

       PPI::Element - The abstract Element class, a base for all source objects

INHERITANCE

         PPI::Element is the root of the PDOM tree

DESCRIPTION

       The abstract "PPI::Element" serves as a base class for all source-related objects, from a
       single whitespace token to an entire document. It provides a basic set of methods to
       provide a common interface and basic implementations.

METHODS

   significant
       Because we treat whitespace and other non-code items as Tokens (in order to be able to
       "round trip" the PPI::Document back to a file) the "significant" method allows us to
       distinguish between tokens that form a part of the code, and tokens that aren't
       significant, such as whitespace, POD, or the portion of a file after (and including) the
       "__END__" token.

       Returns true if the Element is significant, or false it not.

   class
       The "class" method is provided as a convenience, and really does nothing more than
       returning "ref($self)". However, some people have found that they appreciate the laziness
       of "$Foo->class eq 'whatever'", so I have caved to popular demand and included it.

       Returns the class of the Element as a string

   tokens
       The "tokens" method returns a list of PPI::Token objects for the Element, essentially
       getting back that part of the document as if it had not been lexed.

       This also means there are no Statements and no Structures in the list, just the Token
       classes.

   content
       For any "PPI::Element", the "content" method will reconstitute the base code for it as a
       single string. This method is also the method used for overloading stringification. When
       an Element is used in a double-quoted string for example, this is the method that is
       called.

       WARNING:

       You should be aware that because of the way that here-docs are handled, any here-doc
       content is not included in "content", and as such you should not eval or execute the
       result if it contains any PPI::Token::HereDoc.

       The PPI::Document method "serialize" should be used to stringify a PDOM document into
       something that can be executed as expected.

       Returns the basic code as a string (excluding here-doc content).

   parent
       Elements themselves are not intended to contain other Elements, that is left to the
       PPI::Node abstract class, a subclass of "PPI::Element".  However, all Elements can be
       contained within a parent Node.

       If an Element is within a parent Node, the "parent" method returns the Node.

   descendant_of $element
       Answers whether a "PPI::Element" is contained within another one.

       "PPI::Element"s are considered to be descendants of themselves.

   ancestor_of $element
       Answers whether a "PPI::Element" is contains another one.

       "PPI::Element"s are considered to be ancestors of themselves.

   statement
       For a "PPI::Element" that is contained (at some depth) within a PPI::Statement, the
       "statement" method will return the first parent Statement object lexically 'above' the
       Element.

       Returns a PPI::Statement object, which may be the same Element if the Element is itself a
       PPI::Statement object.

       Returns false if the Element is not within a Statement and is not itself a Statement.

   top
       For a "PPI::Element" that is contained within a PDOM tree, the "top" method will return
       the top-level Node in the tree. Most of the time this should be a PPI::Document object,
       however this will not always be so. For example, if a subroutine has been removed from its
       Document, to be moved to another Document.

       Returns the top-most PDOM object, which may be the same Element, if it is not within any
       parent PDOM object.

   document
       For an Element that is contained within a PPI::Document object, the "document" method will
       return the top-level Document for the Element.

       Returns the PPI::Document for this Element, or false if the Element is not contained
       within a Document.

   next_sibling
       All PPI::Node objects (specifically, our parent Node) contain a number of "PPI::Element"
       objects. The "next_sibling" method returns the "PPI::Element" immediately after the
       current one, or false if there is no next sibling.

   snext_sibling
       As per the other 's' methods, the "snext_sibling" method returns the next significant
       sibling of the "PPI::Element" object.

       Returns a "PPI::Element" object, or false if there is no 'next' significant sibling.

   previous_sibling
       All PPI::Node objects (specifically, our parent Node) contain a number of "PPI::Element"
       objects. The "previous_sibling" method returns the Element immediately before the current
       one, or false if there is no 'previous' "PPI::Element" object.

   sprevious_sibling
       As per the other 's' methods, the "sprevious_sibling" method returns the previous
       significant sibling of the "PPI::Element" object.

       Returns a "PPI::Element" object, or false if there is no 'previous' significant sibling.

   first_token
       As a support method for higher-order algorithms that deal specifically with tokens and
       actual Perl content, the "first_token" method finds the first PPI::Token object within or
       equal to this one.

       That is, if called on a PPI::Node subclass, it will descend until it finds a PPI::Token.
       If called on a PPI::Token object, it will return the same object.

       Returns a PPI::Token object, or dies on error (which should be extremely rare and only
       occur if an illegal empty PPI::Statement exists below the current Element somewhere.)

   last_token
       As a support method for higher-order algorithms that deal specifically with tokens and
       actual Perl content, the "last_token" method finds the last PPI::Token object within or
       equal to this one.

       That is, if called on a PPI::Node subclass, it will descend until it finds a PPI::Token.
       If called on a PPI::Token object, it will return the itself.

       Returns a PPI::Token object, or dies on error (which should be extremely rare and only
       occur if an illegal empty PPI::Statement exists below the current Element somewhere.)

   next_token
       As a support method for higher-order algorithms that deal specifically with tokens and
       actual Perl content, the "next_token" method finds the PPI::Token object that is
       immediately after the current Element, even if it is not within the same parent PPI::Node
       as the one for which the method is being called.

       Note that this is not defined as a PPI::Token-specific method, because it can be useful to
       find the next token that is after, say, a PPI::Statement, although obviously it would be
       useless to want the next token after a PPI::Document.

       Returns a PPI::Token object, or false if there are no more tokens after the Element.

   previous_token
       As a support method for higher-order algorithms that deal specifically with tokens and
       actual Perl content, the "previous_token" method finds the PPI::Token object that is
       immediately before the current Element, even if it is not within the same parent PPI::Node
       as this one.

       Note that this is not defined as a PPI::Token-only method, because it can be useful to
       find the token is before, say, a PPI::Statement, although obviously it would be useless to
       want the next token before a PPI::Document.

       Returns a PPI::Token object, or false if there are no more tokens before the "Element".

   clone
       As per the Clone module, the "clone" method makes a perfect copy of an Element object. In
       the generic case, the implementation is done using the Clone module's mechanism itself. In
       higher-order cases, such as for Nodes, there is more work involved to keep the parent-
       child links intact.

   insert_before @Elements
       The "insert_before" method allows you to insert lexical perl content, in the form of
       "PPI::Element" objects, before the calling "Element". You need to be very careful when
       modifying perl code, as it's easy to break things.

       In its initial incarnation, this method allows you to insert a single Element, and will
       perform some basic checking to prevent you inserting something that would be structurally
       wrong (in PDOM terms).

       In future, this method may be enhanced to allow the insertion of multiple Elements,
       inline-parsed code strings or PPI::Document::Fragment objects.

       Returns true if the Element was inserted, false if it can not be inserted, or "undef" if
       you do not provide a "PPI::Element" object as a parameter.

   insert_after @Elements
       The "insert_after" method allows you to insert lexical perl content, in the form of
       "PPI::Element" objects, after the calling "Element". You need to be very careful when
       modifying perl code, as it's easy to break things.

       In its initial incarnation, this method allows you to insert a single Element, and will
       perform some basic checking to prevent you inserting something that would be structurally
       wrong (in PDOM terms).

       In future, this method may be enhanced to allow the insertion of multiple Elements,
       inline-parsed code strings or PPI::Document::Fragment objects.

       Returns true if the Element was inserted, false if it can not be inserted, or "undef" if
       you do not provide a "PPI::Element" object as a parameter.

   remove
       For a given "PPI::Element", the "remove" method will remove it from its parent intact,
       along with all of its children.

       Returns the "Element" itself as a convenience, or "undef" if an error occurs while trying
       to remove the "Element".

   delete
       For a given "PPI::Element", the "delete" method will remove it from its parent,
       immediately deleting the "Element" and all of its children (if it has any).

       Returns true if the "Element" was successfully deleted, or "undef" if an error occurs
       while trying to remove the "Element".

   replace $Element
       Although some higher level class support more exotic forms of replace, at the basic level
       the "replace" method takes a single "Element" as an argument and replaces the current
       "Element" with it.

       To prevent accidental damage to code, in this initial implementation the replacement
       element must be of the same class (or a subclass) as the one being replaced.

   location
       If the Element exists within a PPI::Document that has indexed the Element locations using
       "PPI::Document::index_locations", the "location" method will return the location of the
       first character of the Element within the Document.

       Returns the location as a reference to a five-element array in the form "[ $line,
       $rowchar, $col, $logical_line, $logical_file_name ]". The values are in a human format,
       with the first character of the file located at "[ 1, 1, 1, ?, 'something' ]".

       The second and third numbers are similar, except that the second is the literal horizontal
       character, and the third is the visual column, taking into account tabbing (see "tab_width
       [ $width ]" in PPI::Document).

       The fourth number is the line number, taking into account any "#line" directives.  The
       fifth element is the name of the file that the element was found in, if available, taking
       into account any "#line" directives.

       Returns "undef" on error, or if the PPI::Document object has not been indexed.

   line_number
       If the Element exists within a PPI::Document that has indexed the Element locations using
       "PPI::Document::index_locations", the "line_number" method will return the line number of
       the first character of the Element within the Document.

       Returns "undef" on error, or if the PPI::Document object has not been indexed.

   column_number
       If the Element exists within a PPI::Document that has indexed the Element locations using
       "PPI::Document::index_locations", the "column_number" method will return the column number
       of the first character of the Element within the Document.

       Returns "undef" on error, or if the PPI::Document object has not been indexed.

   visual_column_number
       If the Element exists within a PPI::Document that has indexed the Element locations using
       "PPI::Document::index_locations", the "visual_column_number" method will return the visual
       column number of the first character of the Element within the Document, according to the
       value of "tab_width [ $width ]" in PPI::Document.

       Returns "undef" on error, or if the PPI::Document object has not been indexed.

   logical_line_number
       If the Element exists within a PPI::Document that has indexed the Element locations using
       "PPI::Document::index_locations", the "logical_line_number" method will return the line
       number of the first character of the Element within the Document, taking into account any
       "#line" directives.

       Returns "undef" on error, or if the PPI::Document object has not been indexed.

   logical_filename
       If the Element exists within a PPI::Document that has indexed the Element locations using
       "PPI::Document::index_locations", the "logical_filename" method will return the logical
       file name containing the first character of the Element within the Document, taking into
       account any "#line" directives.

       Returns "undef" on error, or if the PPI::Document object has not been indexed.

TO DO

       It would be nice if "location" could be used in an ad-hoc manner. That is, if called on an
       Element within a Document that has not been indexed, it will do a one-off calculation to
       find the location. It might be very painful if someone started using it a lot, without
       remembering to index the document, but it would be handy for things that are only likely
       to use it once, such as error handlers.

SUPPORT

       See the support section in the main module.

AUTHOR

       Adam Kennedy <adamk@cpan.org>

COPYRIGHT

       Copyright 2001 - 2011 Adam Kennedy.

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

       The full text of the license can be found in the LICENSE file included with this module.