NAME

PerlX::Window - sliding windows on a string or array

SYNOPSIS

   use feature qw(say);
   use PerlX::Window;
   
   my $string = "Foobar";
   
   while (defined window $string, 3)
   {
      say $window;  # says "Foo"
                    # says "oob"
                    # says "oba"
                    # says "bar"
   }

DESCRIPTION

This module provides a sliding window over a long string or array. It exports two functions window and window_pos, and two variables $window and @window.

window $string, $length

Calling this function returns the current window onto the string, and increments the stored position. The window returned is an lvalue which means you can assign to it (like substr).

Once the string has been exhausted, it returns undef (or in list context, the empty list), and resets the stored position for the string.

window @array, $length

Like the string version, but instead of operating on a substring of a string, operates on a slice of an array.

window_pos $string

Returns the position of the most recent window onto the string; a zero-indexed integer.

window_pos @array

Returns the position of the most recent window onto the array; a zero-indexed integer.

window_pos

Called with no arguments, defaults to the string or array from the most recent call to window.

$window

An alias to the current window onto the string that has most recently had window called upon it.

$window is implemented using Variable::Magic if installed, and a tie otherwise.

@window

An alias to the current window onto the array that has most recently had window called upon it.

You may not assign to this in list context, nor perform pop, push, shift, unshift, or slice operations on it, nor any other operation that would change the length of the array. You may however assign to indexes within the array:

   $window[0] = "Fee" if $window[0] eq "Foo";

@window is implemented using a tie.

CAVEATS

window is prototyped (\[$@]$) which means that the first argument must be a literal scalar or array variable, and window will actually fetch a reference to that variable. This means the following are not the same:

   my $tmp = "Foobar";
   say $window
      while window $tmp, 3;

   say $window
      while window my $tmp = "Foobar", 3;

The second example says "Foo" infinitely because $tmp is redefined in each loop, so is a separate variable as far as window is concerned.

This module currently requires Perl 5.16, though I believe that backporting it to Perl 5.8 is feasible.

BUGS

Please report any bugs to http://rt.cpan.org/Dist/Display.html?Queue=PerlX-Window.

SEE ALSO

Data::Iterator::SlidingWindow.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2014 by Toby Inkster.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.