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NAME
Array::Windowed - return a windowed slice of the array
SYNOPSIS
use Array::Windowed qw(windowed_array);
# from an array
my $new_array = array_window @old_array, $start_index, $count);
# from an arrayref
my $new_array2 = &array_window($array_ref, $start_index, $count);
DESCRIPTION
Simple module to return a slice of the passed array as specified by a
start position and a number of elements. Unlike the built in slicing
functions this does not populate the returned array with "undef"s for
out of bounds operations, but simply returns a smaller array.
FUNCTION
Exported on demand (or you can call it fully qualified)
array_windowed @old_array, $start_index, $count
Returns an array reference containing up to $count elements from the
@old_array starting at $start_index.
Unlike a traditional array slice elements outside the bounds of the
array are simply dropped. Negative indexes are treated as normal
indexes that occur before the 0th index (rather than indexes
counting backwards from the start of the array.)
This is probably best shown with a series of examples:
my @array = ['a'..'z'];
# ["a".."z"]
array_windowed(@array, 0, 26);
# ["a","b","c","d","e"]
array_windowed(@array, 0, 5);
# ["b","c","d","e","f"]
array_windowed(@array, 1, 5);
# []
array_windowed(@array, 26, 5);
# []
array_windowed(@array, -50, 5);
# ["x","y","z"]
array_windowed(@array, 23, 5);
# ["a","b","c"]
array_windowed(@array, -2, 5);
# ["a".."z"]
&array_windowed(\@array, 0, 26);
RATIONALLE
Why this module?
Why not simple array slices with @foo[ ... ]
Because the edge cases of indexes outside the bounds of the array
don't do the same thing (they return lots of "undef"s mainly)
Why not splice?
It's destructive on the original array.
Why not Array::Window
Because it tries too hard to DTRT, which isn't the RT for us. For
example, if you have a count bigger than the entire array then it
always returns the entire array irregardless of the start position.
This doesn't mean it's not the module for you, however.
Why not Data::Page
This concept of windowing we're using doesn't use pages, but rather
a start position and a count.
This doesn't mean it's not the module for you, however.
AUTHOR
Written by Mark Fowler <mark@twoshortplanks.com>
COPYRIGHT
Copyright Mark Fowler 2012. All Rights Reserved.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
BUGS
This module does no sanity checking on the values that are passed into
it (i.e. it does not check that $start or $count are integer numbers,
nor does it check that the first argument is an array reference if you
disable prototyping.)
Bugs should be reported via this distribution's CPAN RT queue. This can
be found at <https://rt.cpan.org/Dist/Display.html?Array-Windowed>
You can also address issues by forking this distribution on github and
sending pull requests. It can be found at
<http://github.com/2shortplanks/Array-Windowed>
SEE ALSO
Array::Window, Data::Page
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