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Array::Window - Calculate windows/subsets/pages of arrays. |
source_start()source_end()window_start()window_end()window_length()window_length_desired()previous_start()next_start()previous()next()required()
Array::Window - Calculate windows/subsets/pages of arrays.
# Your search routine returns 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 'Next' or 'Previous' windows? my $Next = $Window->next; my $Previous = $Window->previous;
Many applications require that a large set of results be broken down into a smaller set of 'windows', or 'pages' in web language. Array::Window implements an algorithm specifically for dealing with these windows. It is very flexible and permissive, making adjustments to the window as needed.
Note that this is NOT under Math:: for a reason. It doesn't implement in a pure fashion, it handles idiosyncracies and corner cases specifically relating to the presentation of data.
People will generally refer to the first value in a set as the 1st element, that is, a set containing 10 things will start at 1 and go up to 10. Computers refer to the first value as the '0th' element, with the same set starting at 0 and going up to 9.
The methods for this class return computer orientated values, so if you were to generate a message for a particular window, it might go as follows.
print 'Displaying Widgets ' . ($Window->window_start + 1)
. ' to ' . ($Window->window_end + 1)
. ' of ' . ($Window->source_end + 1);
The inconvenience of this may be addressed in a later version of the module.
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 treated as a range of integers. For a typical 100 element array
@array, you could use one of the following sets of options.
Either
Array::Window->new( source => \@array );
OR
Array::Window->new( source_start => 0, source_end => 99 );
The source value will ONLY be taken as an array reference.
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 be 0.
source_end()Returns the index of the last source value, which for array @array, will be the same as $#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.
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.
previous()This method returns an Array::Window object representing the previous
window, which you can then apply as needed. Returns 0 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 0 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 generate 'next' of 'previous' controls at all.
Applies the object to an array, extracting the subset of the array that the window represents.
Contact the author
- The first_window and last_window methods.
- Determine how many windows there are.
- human_values method to return human readable values.
Adam Kennedy ( maintainer )
cpan@ali.as
http://ali.as/
the Set::Window manpage - For more math orientated windows
Copyright (c) 2002 Adam Kennedy. All rights reserved. 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.
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Array::Window - Calculate windows/subsets/pages of arrays. |