indexing description: "Collections of items, where each item may occur zero or more times, and the number of occurrences is meaningful." names: bag, access access: membership contents: generic deferred class interface BAG [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 feature -- Measurement occurrences (v: G): INTEGER -- Number of times v appears in structure -- (Reference or object equality, -- based on object_comparison.) ensure non_negative_occurrences: Result >= 0 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) extendible: BOOLEAN -- May new items be added? -- (from COLLECTION) 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) 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 -- Element change extend (v: G) -- Add a new occurrence of v. require -- from COLLECTION extendible: extendible ensure -- from COLLECTION item_inserted: has (v) ensure then 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 put (v: G) -- Ensure that structure includes v. -- Was declared in COLLECTION as synonym of put and extend. -- (from COLLECTION) require -- from COLLECTION extendible: extendible ensure -- from COLLECTION item_inserted: has (v) feature -- Removal prune (v: G) -- Remove one occurrence of v if any. -- (Reference or object equality, -- based on object_comparison.) -- (from COLLECTION) require -- from COLLECTION prunable: prunable prune_all (v: G) -- Remove all occurrences of v. -- (Reference or object equality, -- based on object_comparison.) -- (from COLLECTION) require -- from COLLECTION prunable ensure -- from COLLECTION no_more_occurrences: not has (v) 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 CONTAINER) invariant -- from GENERAL reflexive_equality: standard_is_equal (Current); reflexive_conformance: conforms_to (Current); end -- class BAG