indexing description: "Data structures whose items may be compared according to a total order relation" names: comparable_struct access: min, max contents: generic deferred class interface COMPARABLE_STRUCT [G -> COMPARABLE] feature -- Access has (v: like item): BOOLEAN -- Does structure include an occurrence of v? -- (Reference or object equality, -- based on object_comparison.) -- (from LINEAR) ensure -- from CONTAINER not_found_in_empty: Result implies not empty index_of (v: like item; i: INTEGER): INTEGER -- Index of i-th occurrence of v. -- 0 if none. -- (Reference or object equality, -- based on object_comparison.) -- (from LINEAR) require -- from LINEAR positive_occurrences: i > 0 ensure -- from LINEAR non_negative_result: Result >= 0 item: G -- Item at current position -- (from TRAVERSABLE) require -- from TRAVERSABLE not_off: not off require -- from TRAVERSABLE not_off: not off occurrences (v: G): INTEGER -- Number of times v appears. -- (Reference or object equality, -- based on object_comparison.) -- (from LINEAR) off: BOOLEAN -- Is there no current item? -- (from BILINEAR) feature -- Measurement max: like item -- Maximum item require min_max_available min: like item -- Minimum item require min_max_available min_max_available: BOOLEAN -- Can min and max be computed? ensure Result implies not empty feature -- Status report after: BOOLEAN -- Is there no valid position to the right of current one? -- (from LINEAR) changeable_comparison_criterion: BOOLEAN -- May object_comparison be changed? -- (Answer: yes by default.) -- (from CONTAINER) empty: BOOLEAN -- Is there no element? -- (from CONTAINER) exhausted: BOOLEAN -- Has structure been completely explored? -- (from LINEAR) ensure -- from LINEAR exhausted_when_off: off implies Result object_comparison: BOOLEAN -- Must search operations use equal rather than = -- for comparing references? (Default: no, use =.) -- (from CONTAINER) 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 back -- Move to previous position. -- (from BILINEAR) require -- from BILINEAR not_before: not before before: BOOLEAN -- Is there no valid position to the left of current one? -- (from BILINEAR) finish -- Move to last position. -- (from LINEAR) forth -- Move to next position; if no next position, -- ensure that exhausted will be true. -- (from LINEAR) require -- from LINEAR not_after: not after require -- from LINEAR not_after: not after search (v: like item) -- Move to first position (at or after current -- position) where item and v are equal. -- If structure does not include v ensure that -- exhausted will be true. -- (Reference or object equality, -- based on object_comparison.) -- (from BILINEAR) ensure -- from LINEAR object_found: (not exhausted and object_comparison) implies equal (v, item); item_found: (not exhausted and not object_comparison) implies v = item start -- Move to first position if any. -- (from TRAVERSABLE) feature -- Conversion linear_representation: LINEAR [G] -- Representation as a linear structure -- (from LINEAR) invariant -- from GENERAL reflexive_equality: standard_is_equal (Current); reflexive_conformance: conforms_to (Current); empty_constraint: min_max_available implies not empty; -- from BILINEAR not_both: not (after and before); empty_property: empty implies (after or before); before_constraint: before implies off; -- from LINEAR after_constraint: after implies off; -- from TRAVERSABLE empty_constraint: empty implies off; end -- class COMPARABLE_STRUCT