indexing description: "Finite sequences: structures where existing items are arrangedand accessed sequentially, and new ones can be added at the end." names: sequence access: cursor, membership contents: generic deferred class interface SEQUENCE [G] 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: INTEGER -- Index of current position -- (from LINEAR) 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 ACTIVE readable: readable 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) ensure -- from BAG non_negative_occurrences: Result >= 0 off: BOOLEAN -- Is there no current item? -- (from BILINEAR) feature -- Measurement count: INTEGER -- Number of items -- (from FINITE) 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 structure empty? -- (from FINITE) exhausted: BOOLEAN -- Has structure been completely explored? -- (from LINEAR) ensure -- from LINEAR exhausted_when_off: off implies Result extendible: BOOLEAN -- May new items be added? -- (from COLLECTION) full: BOOLEAN -- Is structure filled to capacity? -- (from BOX) object_comparison: BOOLEAN -- Must search operations use equal rather than = -- for comparing references? (Default: no, use =.) -- (from CONTAINER) prunable: BOOLEAN -- May items be removed? -- (from COLLECTION) readable: BOOLEAN -- Is there a current item that may be read? writable: BOOLEAN -- Is there a current item that may be modified? 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 ensure then -- from BILINEAR moved_back: index = old index - 1 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 -- Element change append (s: SEQUENCE [G]) -- Append a copy of s. require argument_not_void: s /= void ensure new_count: count >= old count extend (v: G) -- Add a new occurrence of v. -- (from BAG) require -- from COLLECTION extendible: extendible ensure -- from COLLECTION item_inserted: has (v) ensure then -- from BAG one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1 fill (other: CONTAINER [G]) -- Fill with as many items of other as possible. -- The representations of other and current structure -- need not be the same. -- (from COLLECTION) require -- from COLLECTION other_not_void: other /= void; extendible force (v: like item) -- Add v to end. require extendible: extendible ensure then new_count: count = old count + 1; item_inserted: has (v) put (v: like item) -- Add v to end. require -- from COLLECTION extendible: extendible ensure -- from COLLECTION item_inserted: has (v) ensure then new_count: count = old count + 1 replace (v: G) -- Replace current item by v. -- (from ACTIVE) require -- from ACTIVE writable: writable ensure -- from ACTIVE item_replaced: item = v feature -- Removal prune (v: like item) -- Remove the first occurrence of v if any. -- If no such occurrence go off. require -- from COLLECTION prunable: prunable prune_all (v: like item) -- Remove all occurrences of v; go off. require -- from COLLECTION prunable ensure -- from COLLECTION no_more_occurrences: not has (v) remove -- Remove current item. -- (from ACTIVE) require -- from ACTIVE prunable: prunable; writable: writable wipe_out -- Remove all items. -- (from COLLECTION) require -- from COLLECTION prunable ensure -- from COLLECTION wiped_out: empty 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); -- from ACTIVE writable_constraint: writable implies readable; empty_constraint: empty implies (not readable) and (not writable); -- 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; -- from FINITE empty_definition: empty = (count = 0); non_negative_count: count >= 0; end -- class SEQUENCE