NAME
    Array::Window - Calculate windows/subsets/pages of arrays.

SYNOPSIS
      # Your search routine returns an reference to an array
      # of sorted results of unknown quantity.
      my $results = SomeSearch->find( 'blah' );
  
      # We want to display 20 results at a time
      my $window = Array::Window->new( 
            source        => $results,
            window_start  => 0,
            window_length => 20,
            );
  
      # Do we need to split into pages at all?
      my $show_pages = $window->required;
  
      # Extract the subset from the array
      my $subset = $window->extract( $results );
  
      # Are there 'first', 'last', 'next' or 'previous' windows?
      my $first    = $window->first;
      my $last     = $window->last;
      my $next     = $window->next;
      my $previous = $window->previous;

DESCRIPTION
    Many applications require that a large set of results be broken down
    into a smaller set of 'windows', or 'pages' in web language.
    Array::Window implements an algorithm specifically for dealing with
    these windows. It is very flexible and permissive, making adjustments to
    the window as needed.

    Note that this is NOT under Math:: for a reason. It doesn't implement in
    a pure fashion, it handles idiosyncracies and corner cases specifically
    relating to the presentation of data.

  Values are not in human terms
    People will generally refer to the first value in a set as the 1st
    element, that is, a set containing 10 things will start at 1 and go up
    to 10. Computers refer to the first value as the '0th' element, with the
    same set starting at 0 and going up to 9.

    The normal methods for this class return computer orientated values. If
    you want to generate values for human messages, you should instead use
    the following.

      print 'Displaying Widgets ' . $window->human_window_start
            . ' to ' . $window->human_window_end
            . ' of ' . $window->human_source_end;

METHODS
  new %options
    The "new" constructor is very flexible with regards to the options that
    can be passed to it. However, this generally breaks down into deriving
    two things.

    Firstly, it needs know about the source, usually an array, but more
    generically handled as a range of integers. This means that although the
    "first" element of the array would typically be zero, "Array::Window"
    can handle ranges where the first element is something other than zero.

    For a typical 100 element array @array, you could use any of the
    following sets of options for defining the source array.

      Array::Window->new( source => \@array );
      Array::Window->new( source_length => 100 ); # Assume start at zero
      Array::Window->new( source_start => 0, source_end => 99  );
      Array::Window->new( source_start => 0, source_length => 100 );
      Array::Window->new( source_end => 99,  source_length => 100 );

    Secondly, the object needs to know information about Window it will be
    finding. Assuming a desired window size of 10, and assuming we use the
    first of the two options above, you would end up with the following.

      # EITHER
      Array::Window->new( source => \@array, 
            window_start => 0, window_length => 10 );
  
      # OR
      Array::Window->new( source => \@array,
            window_start => 0, window_end => 9 );

    Although the second option looks a little silly, bear in mind that
    Array::Window will not assume that just because you WANT a window from 0
    - 9, it's actually going to fit the size of the array.

    Please note that the object does NOT make a copy or otherwise retain
    information about the array, so if you change the array later, you will
    need to create a new object.

  source_start
    Returns the index of the first source value, which will usually be 0.

  source_end
    Returns the index of the last source value, which for array @array, will
    be the same as $#array.

  source_length
    Returns the number of elements in the source array.

  window_start
    Returns the index of the first value in the window.

  window_end
    Returns the index of the last value in the window.

  window_length
    Returns the length of the window. This is NOT guarenteed to be the same
    as you initially entered, as the value you entered may have not fit.
    Imagine trying to get a 100 element long window on a 10 element array.
    Something has to give.

  window_length_desired
    Returns the desired window length. i.e. The value you originally
    entered.

  human_window_start
    Returns the index of the first value in the window in human terms ( 1 ..
    n )

  human_window_end
    Returns the index of the last value in the window in human terms ( 1 ..
    n )

  previous_start
    If a 'previous' window can be calculated, this will return the index of
    the start of the previous window.

  next_start
    If a 'next' window can be calculated, this will return the index of the
    start of the next window.

  first
    This method returns an "Array::Window" object representing the first
    window, which you can then use as needed. Returns false if the current
    window is already the first window.

  last
    This method return an "Array::Window" object representing the last
    window, which you can then use as needed. Returns false if the current
    window is already the last window.

  previous
    This method returns an "Array::Window" object representing the previous
    window, which you can then apply as needed. Returns false if the window
    is already at the 'beginning' of the source, and no previous window
    exists.

  next
    This method returns an "Array::Window" object representing the next
    window, which you can apply as needed. Returns false if the window is
    already at the 'end' of the source, and no window exists after this one.

  required
    Looks at the window and source and tries to determine if the entire
    source can be shown without the need for windowing. This can be usefull
    for interface code, as you can avoid generating 'next' or 'previous'
    controls at all.

  extract \@array
    Applies the object to an array, extracting the subset of the array that
    the window represents.

SUPPORT
    Bugs should be reported via the CPAN bug tracker at

    <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Array-Window>

    For other issues, or commercial enhancement or support, contact the
    author.

TO DO
    - Determine how many windows there are.

    - Provide the option to only work at strict intervals

AUTHOR
    Adam Kennedy <adamk@cpan.org>

SEE ALSO
    Set::Window, <http://ali.as/>

COPYRIGHT
    Copyright 2002 - 2008 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.