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 . SEE ALSO Data::Iterator::SlidingWindow. AUTHOR Toby Inkster . 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.