Tie::Array::Lazy - Lazy -- but mutable -- arrays.
use Tie::Array::Lazy;
# 0..Inf
tie my @a, 'Tie::Array::Lazy', [], sub{ $_[0]->index };
print @a[0..9]; # 0123456789
$a[1] = 'one';
print @a[0..9]; # 0one23456789
print "$_\n" for @a; # prints forever
Tie::Array::Lazy implements a lazy array, an array that generates the element on demand. It is a lot like a lazy list but unlike lazy lists seen in many functional languages like Haskell, lazy arrays are mutable so you can assign values to their elements.
The example below explains how it works.
tie my @a, 'Tie::Array::Lazy', [3,2,1,0], sub{ 1 };
my @r = splice @a, 1, 2, qw/two one/
# @r is (2,1); tied(@a)->array is [3,'two','one',0];
pop @a; # 0; tied(@a)->array is [3,'two','one'];
shift @a; # 3; tied(@a)->array is ['two','one'];
shift @a; # 'two'; tied(@a)->array is ['one'];
pop @a; # 'one; tied(@a)->array is [];
pop @a; # 1; tied(@a)->array is [];
@a[3] = 3 # tied(@a)->array is [1,1,1,3];
You can think lazy arrays as arrays that auto-fills.
None.
makes @array a lazy array with its initial state with arrayref and element generator code with coderef. Here is an exmaple;
The coderef is a code reference which $_[0] is the
Tie::Array::Lazy object itself (tied(@array)) and $_[1] is the
index.
In addition to methods that Tie::Array provides, the object has methods below:
-
array
The reference to the internal array which stores values either generated or assigned.
# Fibonacci array tie my @a, 'Tie::Array::Lazy', [0, 1], sub{ $_[0]->array->[-2] + $_[0]->array->[-1] } -
index
Shorthand for
scalar @{ $self->array }.# 0..Inf tie my @a, 'Tie::Array::Lazy', [], sub{ $_[0]->index }; -
maker
The reference to the code reference to generate the value needed. Whenever the value is needed, Tie::Array::Lazy invokes the code below;
$self->maker($self, $index);
Using Tie::Array::Lazy as a base class
Like Tie::Array, you can use this module as a base class. See Tie::Array::Lazier for details.
Dan Kogai, <dankogai at cpan.org>
Please report any bugs or feature requests to
bug-tie-array-lazy at rt.cpan.org, or through the web interface at
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Tie-Array-Lazy.
I will be notified, and then you'll automatically be notified of progress on
your bug as I make changes.
You can find documentation for this module with the perldoc command.
perldoc Tie::Array::Lazy
You can also look for information at:
-
AnnoCPAN: Annotated CPAN documentation
-
CPAN Ratings
-
RT: CPAN's request tracker
-
Search CPAN
Nick Ing-Simmons for Tie::Array
Matsumoto Yukihiro (Matz) for teasing me into hacking this module.
Copyright 2007-2020 Dan Kogai, all rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.