NAME

Template::Plugin::ListOps - Plugin interface to list operations

SYNOPSIS

[% USE ListOps %]

DESCRIPTION

The ListOps plugin attempts to provide a complete set of list operations for use within templates. Initially, I intended this to be a wrapper around the Set::Array module, so much of it's functionality and the naming of the functions come from that. However, the Set::Array module fails due to a weakness in the Want module, so I ended up not using that module at all.

I realize that many of these methods already exist partially as list virtual methods, but this is an attempt to have all of the common (or not so common) list operations in one place. Also, these also have a much more complete handling of duplicate list elements than those in the virtual methods.

METHODS

Unless otherwise stated, the lists that are passed in to the methods are not modified.

Template::Plugin::ListOps makes the following methods available:

unique

[% list = ListOps.unique(list) %]

This removes any duplicates in a list and returns a list containing only unique elements.

compact

[% list = ListOps.compact(list) %]

This removes any undefs from a list and returns a list containing only defined elements.

union

[% list = ListOps.union(list1,list2) %]
[% list = ListOps.union(list1,list2,op) %]

This takes two lists and combines them depending on what "op" is. If op is not given, it defaults to "unique".

If op is "unique", the two lists are combined, but all duplicates are removed.

If op is "duplicates", the lists are strictly added to each other and all duplicates are preserved.

difference

[% list = ListOps.difference(list1,list2) %]
[% list = ListOps.difference(list1,list2,op) %]

This takes two lists and removes the second list from the first. The exact method of this happending depending on what op is. If op is not given, it defaults to "unique".

If op is "unique", every occurence of each of it's elements is removed from the first list.

difference([a a b c],[a],"unique") => (b c)

If op is "duplicates", duplicates are allowed, and the first occurence of each element in the second list is removed from the first list.

difference([a a b c],[a],"duplicates")  => (a b c)

intersection

[% list = ListOps.intersection(list1,list2) %]
[% list = ListOps.intersection(list1,list2,op) %]

This takes two lists and finds the intersection of the two. The intersection are elements that are in both lists. The manner of treating duplicates depends on the value of op. If op is not given, it defaults to "unique".

If op is "unique", a single instance is returned for each value in both lists.

intersection([a a b c],[a a a b],"unique") => (a b)

If op is "duplicates", a single instance is returned for each instance of a value that appears in both lists.

intersection([a a b c],[a a a b],"duplicates") => (a a b)

symmetric_difference

[% list = ListOps.symmetric_difference(list1,list2) %]
[% list = ListOps.symmetric_difference(list1,list2,op) %]

This takes two lists and finds the symmetric difference of the two. The symmetric difference are elements that are in either list, but not both. The manner of treating duplicates depends on the value of op. If op is not given, it defaults to "unique".

If op is "unique", any instance of a value negates all values in the other list.

symmetric_difference([a a b c],[a a a b],"unique") => (c)

If op is "duplicates", a single instance of a value only negates a single value in the other list.

symmetric_difference([a a b c],[a a a b],"duplicates") => (a c)

at

[% ele = ListOps.at(list,pos) %]

This returns the elements at the specified position. Positions are numbered starting at 0.

sorted

[% list = ListOps.sorted(list) %]
[% list = ListOps.sorted(list,method [,arg,arg,...]) %]

This returns the elements of the list sorted based on a method. Sorting is done using the methods defined in the Sort::DataTypes module, refer to that manual for a list of methods, and the description of the method. For example, to use the sort_domain method, use the call:

[% list = ListOps.sorted(list,'domain') %]

All methods are available.

The following methods are available for backwards compatibility:

forward   : same as alphabetic
reverse   : same as rev_alphabetic
forw_num  : same as numerical
rev_num   : same as rev_numerical
dates     : same as date
rev_dates : same as rev_date

If method is not given, it defaults to alphabetic.

join

[% out = ListOps.join(list,string) %]

This returns the elements joined into a string using the given string as a separator.

first, last

[% ele = ListOps.first(list) %]
[% ele = ListOps.last(list) %]

These return the first or last elements of the list.

shiftval, popval

[% ele = ListOps.shiftval(list) %]
[% ele = ListOps.popval(list) %]

These remove the first or last elements of the list and return it.

The lists passed in ARE modified.

unshiftval, pushval

[% list = ListOps.unshiftval(list,vals) %]
[% list = ListOps.pushval(list,vals) %]

These add the vals (which can be a single value or a list of values) to either the start or end of the list.

minval, maxval, minalph, maxalph

[% ele = ListOps.minval(list) %]
[% ele = ListOps.maxval(list) %]
[% ele = ListOps.minalph(list) %]
[% ele = ListOps.maxalph(list) %]

These return the minimum or maximum numerical value in list or the first and last values in an alphabetically sorted list.

impose

[% list = ListOps.impose(list,string,placement) %]

This appends or prepends a string to every element in the list. placement can be "append" or "prepend" (if it is absent, it defaults to "append").

reverse

[% list = ListOps.reverse(list) %]

This reverses the list.

rotate

[% list = ListOps.rotate(list,direction,num) %]

This rotates the list. Each rotation depends on the value of direction which can be ftol or ltof. If it is ftol (the default direction), the first element is removed from the list and added to the end. If it is ltof, the last element is removed and moved to the front of the list.

This will happen num number of times (which defaults to 1).

count

[% num = ListOps.count(list,val) %]

This counts the number of times val appears in the list.

delete

[% list = ListOps.delete(list,val) %]
[% list = ListOps.delete(list,val,op) %]

This deletes occurences of val from the list.

If op is not given, it defaults to "unique".

If op is "unique", every occurence of val is removed from the list.

If op is "duplicates", duplicates are allowed and only the first occurence of val is removed from the list.

is_equal, not_equal

[% flag = ListOps.is_equal(list1,list2) %]
[% flag = ListOps.is_equal(list1,list2,op) %]

[% flag = ListOps.not_equal(list1,list2) %]
[% flag = ListOps.not_equal(list1,list2,op) %]

This takes two lists and tests to see if they are equal or not. The order of the elements is ignored, so (a,b) = (b,a).

If op is not given, it defaults to "unique".

If "op" is "unique", duplicates are ignored, so (a,a,b) = (a,b).

If "op" is "duplicates", the lists are strictly evaluated, and all duplicates are kept.

clear

[% list = ListOps.clear(list) %]

This returns an empty list.

fill

[% list = ListOps.fill(list,val,start,length) %]

This sets elements of a list to be val.

If val is not passed in, it defaults to "". If start is not passed in, it defaults to 0. If length is not passed in, it default to the end of the list. If length refers past the end of the list, new values are added to the end of the list.

splice

[% list = ListOps.splice(list,start,length,vals) %]

This performs the perl splice command on a list.

indexval, rindexval

[% num = ListOps.indexval(list,val) %]
[% num = ListOps.rindexval(list,val) %]

This returns the index of the first/last occurence of val in the list (or undef if the value doesn't occur).

set

[% list = ListOps.set(list,index,val) %]

This sets a specific index to a value.

KNOWN PROBLEMS

None at this point.

LICENSE

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

AUTHOR

Sullivan Beck (sbeck@cpan.org)