indexing description: "Sequential lists whose items are sorted in ascending order according to the relational operators of PART_COMPARABLE" names: sorted_list, sorted_struct, sequence access: index, cursor, membership, min, max contents: generic deferred class interface PART_SORTED_LIST [G -> PART_COMPARABLE] feature -- Access cursor: CURSOR -- Current cursor position -- (from CURSOR_STRUCTURE) first: like item -- Item at first position -- (from CHAIN) require -- from CHAIN not_empty: not empty has (v: G): BOOLEAN -- Does structure include v? -- (Reference or object equality, -- based on object_comparison.) ensure -- from CONTAINER not_found_in_empty: Result implies not empty i_th (i: INTEGER): like item -- Item at i-th position -- Was declared in CHAIN as synonym of i_th and @. -- (from CHAIN) require -- from TABLE valid_key: valid_index (k) index: INTEGER -- Current cursor index -- (from CHAIN) index_of (v: like item; i: INTEGER): INTEGER -- Index of i-th occurrence of item identical to v. -- (Reference or object equality, -- based on object_comparison.) -- 0 if none. -- (from CHAIN) 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 last: like item -- Item at last position -- (from CHAIN) require -- from CHAIN not_empty: not empty occurrences (v: like item): INTEGER -- Number of times v appears. -- (Reference or object equality, -- based on object_comparison.) -- (from CHAIN) ensure -- from BAG non_negative_occurrences: Result >= 0 occurrences (v: like item): INTEGER -- Number of times v appears. -- (Reference or object equality, -- based on object_comparison.) -- (from CHAIN) ensure -- from BAG non_negative_occurrences: Result >= 0 sequential_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 search_after (v: like item) -- Go to first position with item greater -- than or equal to v. ensure argument_less_than_item: (not after) implies (v <= item) search_before (v: like item) -- Go to last position with item less -- than or equal to v. ensure (not off) implies (item <= v) infix "@" (i: INTEGER): like item -- Item at i-th position -- Was declared in CHAIN as synonym of i_th and @. -- (from CHAIN) require -- from TABLE valid_key: valid_index (k) feature -- Measurement count: INTEGER -- Number of items -- (from FINITE) feature -- Status report after: BOOLEAN -- Is there no valid cursor position to the right of cursor? -- (from LIST) before: BOOLEAN -- Is there no valid cursor position to the left of cursor? -- (from LIST) 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) isfirst: BOOLEAN -- Is cursor at first position? -- (from CHAIN) ensure -- from CHAIN valid_position: Result implies not empty islast: BOOLEAN -- Is cursor at last position? -- (from CHAIN) ensure -- from CHAIN valid_position: Result implies not empty 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 CHAIN) prunable: BOOLEAN -- May items be removed? -- (from COLLECTION) readable: BOOLEAN -- Is there a current item that may be read? -- (from SEQUENCE) sorted: BOOLEAN valid_cursor (p: CURSOR): BOOLEAN -- Can the cursor be moved to position p? -- (from CURSOR_STRUCTURE) valid_cursor_index (i: INTEGER): BOOLEAN -- Is i correctly bounded for cursor movement? -- (from CHAIN) ensure -- from CHAIN valid_cursor_index_definition: Result = ((i >= 0) and (i <= count + 1)) valid_index (i: INTEGER): BOOLEAN -- Is i within allowable bounds? -- (from CHAIN) ensure then -- from CHAIN valid_index_definition: Result = ((i >= 1) and (i <= count)) writable: BOOLEAN -- Is there a current item that may be modified? -- (from SEQUENCE) 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 require -- from BILINEAR not_before: not before ensure then -- from BILINEAR moved_back: index = old index - 1 ensure then -- from BILINEAR moved_back: index = old index - 1 finish -- Move cursor to last position. -- (No effect if empty) -- (from CHAIN) ensure then -- from CHAIN at_last: not empty implies islast forth -- Move to next position; if no next position, -- ensure that exhausted will be true. -- (from LIST) require -- from LINEAR not_after: not after ensure then -- from LIST moved_forth: index = old index + 1 go_i_th (i: INTEGER) -- Move cursor to i-th position. -- (from CHAIN) require -- from CHAIN valid_cursor_index: valid_cursor_index (i) ensure -- from CHAIN position_expected: index = i go_to (p: CURSOR) -- Move cursor to position p. -- (from CURSOR_STRUCTURE) require -- from CURSOR_STRUCTURE cursor_position_valid: valid_cursor (p) move (i: INTEGER) -- Move cursor i positions. The cursor -- may end up off if the absolute value of i -- is too big. -- (from CHAIN) ensure -- from CHAIN too_far_right: (old index + i > count) implies exhausted; too_far_left: (old index + i < 1) implies exhausted; expected_index: (not exhausted) implies (index = old index + i) 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 cursor to first position. -- (No effect if empty) -- (from CHAIN) ensure then -- from CHAIN at_first: not empty implies isfirst feature -- Element change append (s: SEQUENCE [G]) -- Append a copy of s. -- (from SEQUENCE) require -- from SEQUENCE argument_not_void: s /= void ensure -- from SEQUENCE new_count: count >= old count extend (v: like item) -- Put v at proper position in list. -- The cursor ends up on the newly inserted -- item. 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 ensure then remains_sorted: (old sorted) implies sorted; item_inserted: item = v 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. -- (from SEQUENCE) require -- from SEQUENCE extendible: extendible ensure then -- from SEQUENCE new_count: count = old count + 1; item_inserted: has (v) merge (other: LINEAR [G]) -- Add all items from other at their proper positions. ensure then remains_sorted: (old sorted) implies sorted put (v: like item) -- Replace current item by v. -- (Synonym for replace) -- (from CHAIN) require -- from COLLECTION extendible: extendible ensure -- from COLLECTION item_inserted: has (v) ensure then -- from CHAIN same_count: count = old count put_i_th (v: like item; i: INTEGER) -- Put v at i-th position. -- (from CHAIN) require -- from TABLE valid_key: valid_index (k) ensure then -- from INDEXABLE insertion_done: i_th (k) = v replace (v: G) -- Replace current item by v. -- (from ACTIVE) require -- from ACTIVE writable: writable require -- from ACTIVE writable: writable ensure -- from ACTIVE item_replaced: item = v 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. -- (from SEQUENCE) require -- from COLLECTION prunable: prunable prune_all (v: like item) -- Remove all occurrences of v; go off. -- (from SEQUENCE) require -- from COLLECTION prunable ensure -- from COLLECTION no_more_occurrences: not has (v) wipe_out -- Remove all items. -- (from COLLECTION) require -- from COLLECTION prunable require -- from COLLECTION prunable ensure -- from COLLECTION wiped_out: empty ensure -- from COLLECTION wiped_out: empty feature -- Transformation swap (i: INTEGER) -- Exchange item at i-th position with item -- at cursor position. -- (from CHAIN) require -- from CHAIN not_off: not off; valid_index: valid_index (i) ensure -- from CHAIN swapped_to_item: item = old i_th (i); swapped_from_item: i_th (i) = old item feature -- Conversion linear_representation: LINEAR [G] -- Representation as a linear structure -- (from LINEAR) feature -- Duplication duplicate (n: INTEGER): like Current -- Copy of sub-chain beginning at current position -- and having min (n, from_here) items, -- where from_here is the number of items -- at or to the right of current position. -- (from CHAIN) require -- from CHAIN not_off_unless_after: off implies after; valid_subchain: n >= 0 invariant -- from GENERAL reflexive_equality: standard_is_equal (Current); reflexive_conformance: conforms_to (Current); -- from LIST before_definition: before = (index = 0); after_definition: after = (index = count + 1); -- from CHAIN non_negative_index: index >= 0; index_small_enough: index <= count + 1; off_definition: off = ((index = 0) or (index = count + 1)); isfirst_definition: isfirst = ((not empty) and (index = 1)); islast_definition: islast = ((not empty) and (index = count)); item_corresponds_to_index: (not off) implies (item = i_th (index)); -- 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 PART_SORTED_LIST