indexing description: "Hierarchical structures in which each item has zero or one immediate predecessor, and zero or more successors." names: hierarchical, traversing access: cursor contents: generic deferred class interface HIERARCHICAL [G] feature -- Access has (v: G): BOOLEAN -- Does structure include v? -- (Reference or object equality, -- based on object_comparison.) -- (from CONTAINER) ensure -- from CONTAINER not_found_in_empty: Result implies not empty item: G -- Item at current position -- (from TRAVERSABLE) require -- from TRAVERSABLE not_off: not off successor_count: INTEGER -- Number of successors of current element require not_off: not off feature -- Status report changeable_comparison_criterion: BOOLEAN -- May object_comparison be changed? -- (Answer: yes by default.) -- (from CONTAINER) empty: BOOLEAN -- Is there no element? -- (from CONTAINER) object_comparison: BOOLEAN -- Must search operations use equal rather than = -- for comparing references? (Default: no, use =.) -- (from CONTAINER) off: BOOLEAN -- Is there no current item? -- (from TRAVERSABLE) feature -- Status setting compare_objects -- Ensure that future search operations will use equal -- rather than = for comparing references. -- (from CONTAINER) require -- from CONTAINER changeable_comparison_criterion ensure -- from CONTAINER object_comparison compare_references -- Ensure that future search operations will use = -- rather than equal for comparing references. -- (from CONTAINER) require -- from CONTAINER changeable_comparison_criterion ensure -- from CONTAINER reference_comparison: not object_comparison feature -- Cursor movement down (i: INTEGER) -- Move to i-th successor. require not_off: not off; argument_within_bounds: i >= 1 and i <= successor_count start -- Move to first position if any. -- (from TRAVERSABLE) up -- Move to predecessor. require not_off: not off feature -- Conversion linear_representation: LINEAR [G] -- Representation as a linear structure -- (from CONTAINER) invariant -- from GENERAL reflexive_equality: standard_is_equal (Current); reflexive_conformance: conforms_to (Current); non_negative_successor_count: successor_count >= 0; -- from TRAVERSABLE empty_constraint: empty implies off; end -- class HIERARCHICAL