SYNOPSIS
	mapping filter_indices(mapping, string func, object ob, ...)
	mapping filter_indices(mapping, closure cl, ...)

DESCRIPTION
	ob->func() is called resp. cl applied to every element in the
	mapping, with first argument being the key of the
	element, and then the extra args that were given to
	filter_mapping. If the function returns true, the element is
	added to the result mapping. ob can also be a file_name of an
	object. If the second arg is a string and the third is not an
	object, this_object() will be used as default.

HISTORY
        In LDMud 3.2.6 renamed from filter_mapping() and generalised
        by efun filter().

SEE ALSO
	filter(E), map(E), map_indices(E), walk_mapping(E), member(E),
	m_contains(E)
