NAME

List::Haystack - A immutable list utility to find element

SYNOPSIS

Basic (not lazy mode)

    use List::Haystack;

    my $haystack = List::Haystack->new([qw/foo bar foo/]); # <= create internal structure here

    $haystack->find('foo'); # <= 1 (true value)
    $haystack->find('bar'); # <= 1 (true value)
    $haystack->find('xxx'); # <= 0 (false value)

    $haystack->cnt('foo'); # <= 2 (number of occurrences)
    $haystack->cnt('bar'); # <= 1 (number of occurrences)
    $haystack->cnt('xxx'); # <= 0 (number of occurrences)

Lazy

    use List::Haystack;

    my $haystack = List::Haystack->new([qw/foo bar foo/], {lazy => 1});

    $haystack->find('foo'); # <= 1 (true value, create internal structure here)
    $haystack->find('bar'); # <= 1 (true value)
    $haystack->find('xxx'); # <= 0 (false value)

    $haystack->cnt('foo'); # <= 2 (number of occurrences)
    $haystack->cnt('bar'); # <= 1 (number of occurrences)
    $haystack->cnt('xxx'); # <= 0 (number of occurrences)

DESCRIPTION

List::Haystack is a utility to find element for list. This module works immutably.

This module converts the given list to internal structure to find the element fast. This conversion runs only at once. That is to say, if you want to modify the target of list, you must create new instance of this module.

METHODS

new($list: ArrayRef|undef, $option: HashRef): List::Haystack

A constructor. $list is a target of list to find. It must be ArrayRef or undef; if undef is given, find and cnt always return 0.

$option is an HashRef argument of option. If you specify lazy, it puts off creation the internal structure until instance method is called (i.e. constructor doesn't create internal structure).

e.g. List::Haystack->new([...], {lazy => 1}

haystack(): HashRef

A getter method. This method returns a HashRef that contains element as key and number of occurrences as value.

find($element: Any): Bool

This method returns whether given list contains $element or not.

cnt($element: Any): Int

This method returns number of occurrences of given $element.

LICENSE

Copyright (C) moznion.

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

AUTHOR

moznion <moznion@gmail.com>