Provided by: libarray-iterator-perl_0.11-2_all 
NAME
Array::Iterator - A simple class for iterating over Perl arrays
VERSION
version 0.11
SYNOPSIS
use Array::Iterator;
# create an iterator with an array
my $i = Array::Iterator->new(1 .. 100);
# create an iterator with an array reference
my $i = Array::Iterator->new(\@array);
# create an iterator with a hash reference
my $i = Array::Iterator->new({ __array__ => \@array });
# a base iterator example
while ($i->has_next()) {
if ($i->peek() < 50) {
# ... do something because
# the next element is over 50
}
my $current = $i->next();
# ... do something with current
}
# shortcut style
my @accumulation;
push @accumulation => { item => $iterator->next() } while $iterator->has_next();
# C++ ish style iterator
for (my $i = Array::Iterator->new(@array); $i->has_next(); $i->next()) {
my $current = $i->current();
# .. do something with current
}
# common perl iterator idiom
my $current;
while ($current = $i->get_next()) {
# ... do something with $current
}
DESCRIPTION
This class provides a very simple iterator interface. It is is uni-directional and can
only be used once. It provides no means of reverseing or reseting the iterator. It is not
recommended to alter the array during iteration, however no attempt is made to enforce
this (although I will if I can find an efficient means of doing so). This class only
intends to provide a clear and simple means of generic iteration, nothing more (yet).
METHODS
Public Methods
new (@array | $array_ref | $hash_ref)
The constructor can be passed either a plain perl array, an array reference, or a hash
reference (with the array specified as a single key off the hash, __array__). Single
element arrays are not supported by either of the first two calling conventions, since
it is not possible to distinguish between an array of a single element which happens
to be an array reference, and an array reference of a single element, thus previous
versions of the constructor would raise an exception. If you expect to pass arrays to
the constructor which may have only a single element, then the array can be passed as
the element of a HASH reference, with the key, __array__:
my $i = Array::Iterator->new({ __array__ => \@array });
has_next([$n])
This methods returns a boolean. True (1) if there are still more elements in the
iterator, false (0) if there are not.
Takes an optional positive integer (> 0) that specifies the position you want to
check. This allows you to check if there an element at arbitrary position. Think of
it as an ordinal number you want to check:
$i->has_next(2); # 2nd next element
$i->has_next(10); # 10th next element
Note that has_next(1) is the same as "has_next()".
Throws an exception if $n <= 0.
next
This method returns the next item in the iterator, be sure to only call this once per
iteration as it will advance the index pointer to the next item. If this method is
called after all elements have been exhausted, an exception will be thrown.
get_next
This method returns the next item in the iterator, be sure to only call this once per
iteration as it will advance the index pointer to the next item. If this method is
called after all elements have been exhausted, it will return undef.
This method was added to allow for a faily common perl iterator idiom of:
my $current;
while ($current = $i->get_next()) {
...
}
In this the loop terminates once $current is assigned to a false value. The only
problem with this idiom for me is that it does not allow for undefined or false values
in the iterator. Of course, if this fits your data, then there is no problem.
Otherwise I would recommend the "has_next"/"next" idiom instead.
peek([$n])
This method can be used to peek ahead at the next item in the iterator. It is non-
destructuve, meaning it does not advance the internal pointer. If this method is
called and attempts to reach beyond the bounds of the iterator, it will return undef.
Takes an optional positive integer (> 0) that specifies how far ahead you want to
peek:
$i->peek(2); # gives you 2nd next element
$i->peek(10); # gives you 10th next element
Note that peek(1) is the same as "peek()".
Throws an exception if $n <= 0.
NOTE: Prior to version 0.03 this method would throw an exception if called out of
bounds. I decided this was not a good practice, as it made it difficult to be able to
peek ahead effectively. This not the case when calling with an argument that is <= 0
though, as it's clearly a sign of incorrect usage.
current
This method can be used to get the current item in the iterator. It is non-
destructive, meaning that it does not advance the internal pointer. This value will
match the last value dispensed by "next" or "get_next".
current_index
This method can be used to get the current index in the iterator. It is non-
destructive, meaning that it does not advance the internal pointer. This value will
match the index of the last value dispensed by "next" or "get_next".
get_length
This is a basic accessor for getting the length of the array being iterated over.
Protected Methods
These methods are protected, in the Java/C++ sense of the word. They can only be called
internally by subclasses of Array::Iterator, an exception is thrown if that condition is
violated. They are documented here only for people interested in subclassing
Array::Iterator.
_current_index
An lvalue-ed subroutine which allows access to the iterator's internal pointer.
_iteratee
This returns the item being iteratated over, in our case an array.
_get_item ($iteratee, $index)
This method is used by all other routines to access items with. Given the iteratee and
an index, it will return the item being stored in the $iteratee at the index of
$index.
TO DO
Improve BiDirectional Test suite
I want to test the back and forth a little more, make sure they work well with one
another.
Other Iterators
Array::Iterator::BiDirectional::Circular, Array::Iterator::Skipable and
Array::Iterator::BiDirectional::Skipable are just a few ideas I have had. I am going
to hold off for now until I am sure they are actually useful.
BUGS
None that I am aware of. The code is pretty thoroughly tested (see "CODE COVERAGE" below)
and is based on an (non-publicly released) module which I had used in production systems
for about 2 years without incident. Of course, if you find a bug, let me know, and I will
be sure to fix it.
CODE COVERAGE
I use Devel::Cover to test the code coverage of my tests, below is the Devel::Cover report
on this module's test suite.
------------------------------- ------ ------ ------ ------ ------ ------ ------
File stmt bran cond sub pod time total
------------------------------- ------ ------ ------ ------ ------ ------ ------
Array/Iterator.pm 100.0 100.0 66.7 100.0 100.0 67.6 98.2
Array/Iterator/BiDirectional.pm 100.0 100.0 n/a 100.0 100.0 20.2 100.0
Array/Iterator/Circular.pm 100.0 100.0 n/a 100.0 100.0 7.1 100.0
Array/Iterator/Reusable.pm 100.0 n/a n/a 100.0 100.0 5.0 100.0
------------------------------- ------ ------ ------ ------ ------ ------ ------
Total 100.0 100.0 66.7 100.0 100.0 100.0 99.0
------------------------------- ------ ------ ------ ------ ------ ------ ------
SEE ALSO
This module now includes several subclasses of Array::Iterator which add certain behaviors
to Array::Iterator, they are:
Array::Iterator::BiDirectional
Adds the ability to move backwards and forwards through the array.
Array::Iterator::Circular
When this iterator reaches the end of its list, it will loop back to the start again.
Array::Iterator::Reusable
This iterator can be reset to its beginning and used again.
The Design Patterns book by the Gang of Four, specifically the Iterator pattern.
Some of the interface for this class is based upon the Java Iterator interface.
OTHER ITERATOR MODULES
There are a number of modules on CPAN with the word Iterator in them. Most of them are
actually iterators included inside other modules, and only really useful within that
parent modules context. There are however some other modules out there that are just for
pure iteration. I have provided a list below of the ones I have found, if perhaps you
don't happen to like the way I do it.
Tie::Array::Iterable
This module ties the array, something we do not do. But it also makes an attempt to
account for, and allow the array to be changed during iteration. It accomplishes this
control because the underlying array is tied. As we all know, tie-ing things can be a
performance issue, but if you need what this module provides, then it will likely be
an acceptable compromise. Array::Iterator makes no attempt to deal with this mid-
iteration manipulation problem. In fact it is recommened to not alter your array with
Array::Iterator, and if possible we will enforce this in later versions.
Data::Iter
This module allows for simple iteratation over both hashes and arrays. It does it by
importing several functions which can be used to loop over either type (hash or array)
in the same way. It is an interesting module, it differs from Array::Iterator in
paradigm (Array::Iterator is more OO) as well as in intent.
Class::Iterator
This is essentially a wrapper around a closure based iterator. This method can be very
flexible, but at times is difficult to manage due to the inherent complextity of using
closures. I actually was a closure-as-iterator fan for a while, but eventually moved
away from it in favor of the more plain vanilla means of iteration, like that found
Array::Iterator.
Class::Iter
This is part of the Class::Visitor module, and is a Visitor and Iterator extensions to
Class::Template. Array::Iterator is a standalone module not associated with others.
Data::Iterator::EasyObj
Data::Iterator::EasyObj makes your array of arrays into iterator objects. It also has
the ability to further nest additional data structures including
Data::Iterator::EasyObj objects. Array::Iterator is one dimensional only, and does not
attempt to do many of the more advanced features of this module.
ACKNOWLEDGEMENTS
Thanks to Hugo Cornelis for pointing out a bug in "peek()"
Thanks to Phillip Moore for providing the patch to allow single element iteration through
the hash-ref constructor parameter.
ORIGINAL AUTHOR
stevan little, <stevan@iinteractive.com>
ORIGINAL COPYRIGHT AND LICENSE
Copyright 2004, 2005 by Infinity Interactive, Inc.
<http://www.iinteractive.com>
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
AUTHOR
Steven Haryanto <stevenharyanto@gmail.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2013 by Steven Haryanto.
This is free software; you can redistribute it and/or modify it under the same terms as
the Perl 5 programming language system itself.