indexing
	description: "Cursors for structure traversals"
	library: "Gobo Eiffel Structure Library"
	author: "Eric Bezault <ericb@gobo.demon.co.uk>"
	copyright: "Copyright (c) 1997, Eric Bezault"

deferred class interface
	DS_CURSOR [G]

feature -- Access

	container: DS_TRAVERSABLE [G]
			-- Structure traversed

	item: G
			-- Item at cursor position
		require
			valid_cursor: is_valid;
			not_off: not off
	
feature -- Status report

	is_valid: BOOLEAN
			-- Is cursor valid?
			-- (A cursor might become invalid if container
			-- has been modified during traversal.)

	off: BOOLEAN
			-- Is there no item at cursor position?
		require
			valid_cursor: is_valid
	
invariant

		-- from GENERAL
	reflexive_equality: standard_is_equal (Current);
	reflexive_conformance: conforms_to (Current);
	container_not_void: container /= void;
	empty_constraint: container.is_empty implies off;

end -- class DS_CURSOR