SYNOPSIS
        mixed unique_array(object *obarr, string|closure fun)
        mixed unique_array(object *obarr, string|closure fun, mixed skip)
        mixed unique_array(object *obarr, string|closure fun, mixed extra...
                                        , mixed skip)

DESCRIPTION
        Groups objects together for which the separator function returns the
        same value. obarr should be an array of objects, other types are
        ignored.
        
        If the separator function is defined by name, it is searched and
        called in the objects from <obarr>. If <extra> arguments are given,
        they are passed to the function as arguments.
        
        If the separator function is defined as a closure, it will be passed
        the objects from <obarr> as first argument, with the <extra> arguments
        (if any) passed following.
        
        If the <skip> argument is given (it is required when <extra> arguments
        are to be used), and the return value from the separator function call
        matches this value, the object in question will _not_ be included in
        the returned array. Default value for <skip> is the number 0.

        The returned array is an array of arrays of objects in the form:

        ({ ({ Same1:1, Same1:2, ... Same1:N }),
           ({ Same2:1, Same2:2, ... Same2:N }),
              ....
           ({ SameM:1, SameM:2, ... SameM:N }) })

EXAMPLES
        mixed *arr;
        arr=unique_array(users(), "_query_level", -1);

        This will return an array of arrays holding all user objects
        grouped together by their user levels. Wizards have a user
        level of -1 so they will not appear in the the returned array.

HISTORY
        LDMud 3.3 added the possibility to call closures, and to
          pass extra arguments to the separator function.

SEE ALSO
        filter(E), map(E)