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

SYNOPSIS
       [% USE ListOps %]

DESCRIPTION
    The ListOps plugin provides some nice list operations for use within
    templates. I wanted to use the Set::Array module directly, but it fails
    due to a weakness in the Want module. When/if this is fixed, I will
    probably replace the routines with calls to that module.

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

METHODS
    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) %]

        This returns the elements of the list sorted based on a method. The
        following methods are known:

           forward   : alphabetical order
           reverse   : reverse alphabetical order
           forw_num  : numerical order
           rev_num   : reverse numerical order
           random    : sorts them in random order

        The following methods are also available for specific data types:

           ip        : sort IPs
           dates     : sort dates in chronological order
           rev_dates : sort dates in reverse chronological order.

        If method is not given, it defaults to forward.

    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.

    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) %]

        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) %]

        This deletes all occurences of val 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.

AUTHOR
    Sullivan Beck (sbeck@cpan.org)

