NAME

       PPI::Structure - The base class for Perl braced structures

INHERITANCE

         PPI::Structure
         isa PPI::Node
             isa PPI::Element

DESCRIPTION

       PPI::Structure is the root class for all Perl bracing structures. This covers all forms of
       " [ ... ] ", " { ... } ", and " ( ... ) " brace types, and includes cases where only one
       half of the pair exist.

       The class PPI::Structure itself is full abstract and no objects of that type should
       actually exist in the tree.

   Elements vs Children
       A PPI::Structure has an unusual existence. Unlike a PPI::Document or PPI::Statement, which
       both simply contain other elements, a structure both contains and consists of content.

       That is, the brace tokens are not considered to be "children" of the structure, but are
       part of it.

       In practice, this will mean that while the ->elements and ->tokens methods (and related)
       will return a list with the brace tokens at either end, the ->children method explicitly
       will not return the brace.

STRUCTURE CLASSES

       Excluding the transient PPI::Structure::Unknown that exists briefly inside the parser,
       there are eight types of structure.

   PPI::Structure::List
       This covers all round braces used for function arguments, in "foreach" loops, literal
       lists, and braces used for precedence-ordering purposes.

   PPI::Structure::For
       Although not used for the "foreach" loop list, this is used for the special case of the
       round-brace three-part semicolon-separated "for" loop expression (the traditional C style
       for loop).

   PPI::Structure::Given
       This is for the expression being matched in switch statements.

   PPI::Structure::When
       This is for the matching expression in "when" statements.

   PPI::Structure::Condition
       This round-brace structure covers boolean conditional braces, such as for "if" and "while"
       blocks.

   PPI::Structure::Block
       This curly-brace and common structure is used for all form of code blocks. This includes
       those for "if", "do" and similar, as well as "grep", "map", "sort", "sub" and (labelled or
       anonymous) scoping blocks.

   PPI::Structure::Constructor
       This class covers brace structures used for the construction of anonymous "ARRAY" and
       "HASH" references.

   PPI::Structure::Subscript
       This class covers square-braces and curly-braces used after a -> pointer to access the
       subscript of an "ARRAY" or "HASH".

METHODS

       "PPI::Structure" itself has very few methods. Most of the time, you will be working with
       the more generic PPI::Element or PPI::Node methods, or one of the methods that are
       subclass-specific.

   start
       For lack of better terminology (like "open" and "close") that has not already in use for
       some other more important purpose, the two individual braces for the structure are known
       within PPI as the "start" and "finish" braces (at least for method purposes).

       The "start" method returns the start brace for the structure (i.e. the opening brace).

       Returns the brace as a PPI::Token::Structure or "undef" if the structure does not have a
       starting brace.

       Under normal parsing circumstances this should never occur, but may happen due to
       manipulation of the PDOM tree.

   finish
       The "finish" method returns the finish brace for the structure (i.e. the closing brace).

       Returns the brace as a PPI::Token::Structure or "undef" if the structure does not have a
       finishing brace. This can be quite common if the document is not complete (for example,
       from an editor where the user may be halfway through typeing a subroutine).

   braces
       The "braces" method is a utility method which returns the brace type, regardless of
       whether both or just one of the braces is defined.

       Returns one of the three strings '[]', '{}', or '()', or "undef" on error (primarily not
       having a start brace, as mentioned above).

complete

       The "complete" method is a convenience method that returns true if the both braces are
       defined for the structure, or false if only one brace is defined.

       Unlike the top level "complete" method which checks for completeness in depth, the
       structure complete method ONLY confirms completeness for the braces, and does not recurse
       downwards.

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.