    deferred class
    	BILINEAR [G]

    General
    	cluster: base
    	description: "Structures that may be traversed forward and backward"

    Ancestors
    	LINEAR* [G]
    	LINEAR* [G]

    Queries
    	after: BOOLEAN
    	before: BOOLEAN
    	changeable_comparison_criterion: BOOLEAN
    	exhausted: BOOLEAN
    	for_all (test: FUNCTION [ANY, TUPLE [G], BOOLEAN]): BOOLEAN
    	has (v: [like item] G): BOOLEAN
    	index: INTEGER_32
    	index_of (v: [like item] G; i: INTEGER_32): INTEGER_32
    	is_empty: BOOLEAN
    	item: G
    	linear_representation: LINEAR [G]
    	object_comparison: BOOLEAN
    	occurrences (v: [like item] G): INTEGER_32
    	off: BOOLEAN
    	there_exists (test: FUNCTION [ANY, TUPLE [G], BOOLEAN]): BOOLEAN

    Commands
    	back
    	compare_objects
    	compare_references
    	do_all (action: PROCEDURE [ANY, TUPLE [G]])
    	do_if (action: PROCEDURE [ANY, TUPLE [G]]; test: FUNCTION [ANY, TUPLE [G], BOOLEAN])
    	finish
    	forth
    	search (v: [like item] G)
    	start

    Constraints
    	not both
    	before constraint