note description: "SET data structure for both specification and implementation." author: "JSO and JW" class interface SET [G -> attached ANY] create make_empty, make_from_array, make_one convert make_from_array ({ARRAY [G]}), as_array: {ARRAY [G]} feature -- Constructor make_empty -- Initialize an empty set. ensure is_empty make_one (a_singleton: G) -- make a singleton set ensure count = 1 has (a_singleton) make_from_array (a: ARRAY [G]) ensure all_items_are_intended: across Current as it all a.has (it.item) end all_intended_items_added: across a as it all Current.has (it.item) end feature -- Conversion to array. -- as_array: ARRAY[G] -- do -- create Result.make_empty -- across -- Current as c -- loop -- Result.force (c.item, Result.upper + 1) -- end ---- Result.compare_objects -- ensure -- Current ~ create {SET[G]}.make_from_array (Result) -- -- why does this fail in {REL}.t8 -- end as_array: ARRAY [G] feature -- Iteration new_cursor: ITERATION_CURSOR [G] -- Fresh cursor associated with current structure feature -- Query and command for arbitrary set members chosen: BOOLEAN item: G -- Return an arbitrary member from the set. require not is_empty chosen ensure has (Result) choose_item -- Choose an arbitrary element of the -- set and store it in item require not is_empty ensure has (item) chosen remove_item -- Remove an arbitrary member (i.e., 'item') from the set. require not is_empty chosen ensure Current ~ old Current.deep_twin - old item not chosen feature -- Commands for implementation extend (g: G) -- Extend the current set by 'g'. ensure case_of_no_extension: (old Current.deep_twin).has (g) implies old Current.deep_twin ~ Current case_of_extension: not (old Current.deep_twin).has (g) implies old Current.deep_twin ~ Current - g union (other: like Current) -- Extend the current set by 'other'. ensure old Current.deep_twin |<: Current other |<: Current definition: hold_count (agent in_either_set (?, old Current.deep_twin, other)) = count subtract (g: G) -- Subtract the current set by 'g'. ensure case_of_subtraction: (old Current.deep_twin).has (g) implies old Current.deep_twin ~ Current + g case_of_no_subtraction: not (old Current.deep_twin).has (g) implies old Current.deep_twin ~ Current difference (other: like Current) -- Subtract the current set by 'other'. ensure definition: old Current.deep_twin ~ Current |\/| (old Current.deep_twin |/\| other) intersect (other: like Current) -- Intersect current set with 'other'. ensure Current |<: old Current.deep_twin Current |<: other definition: hold_count (agent in_both_set (?, old Current.deep_twin, other)) = count feature -- Queries for specification. count alias "#": INTEGER_32 -- Return the cardinality of the set. ensure current_set_unchanged: Current ~ old Current.deep_twin definition: Result = hold_count (agent g_to_true) is_empty: BOOLEAN -- Is the set empty? ensure current_set_unchanged: Current ~ old Current.deep_twin Result = (# Current = 0) has (g: G): BOOLEAN -- Does the set contain 'g'? ensure current_set_unchanged: Current ~ old Current.deep_twin definition_1: Result = (hold_count (agent eq (?, g)) = 1) definition_2: Result = across Current as it some it.item ~ g end is_subset_of alias "|<:" (other: like Current): BOOLEAN ensure current_set_unchanged: Current ~ old Current.deep_twin Result = across Current as cur all other.has (cur.item) end extended alias "+" (g: G): like Current -- Return a new set representing the addtion of current and 'g'. ensure current_set_unchanged: Current ~ old Current.deep_twin case_of_no_extension: has (g) implies Current ~ Result case_of_extension: not has (g) implies Current ~ Result - g unioned alias "|\/|" (other: like Current): like Current -- Return a new set representing the union of current and 'other'. ensure current_set_unchanged: Current ~ old Current.deep_twin items_from_either_set: across Result as it all Current.has (it.item) or other.has (it.item) end subtracted alias "-" (g: G): like Current -- Return a new set representing the difference between Current and 'other'. ensure current_set_unchanged: Current ~ old Current.deep_twin case_of_subtraction: has (g) implies Current ~ Result + g case_of_no_subtraction: not has (g) implies Current ~ Result differenced alias "|\" (other: like Current): like Current -- Return a new set representing the difference between Current and 'other'. ensure current_set_unchanged: Current ~ old Current.deep_twin definition: Current ~ Result |\/| (Current |/\| other) intersected alias "|/\|" (other: like Current): like Current -- Return a new set representing the intersection of current and 'other'. ensure current_set_unchanged: Current ~ old Current.deep_twin items_from_both_set: across Result as it all Current.has (it.item) and other.has (it.item) end feature -- Quantifiers hold_count (exp: PREDICATE [G]): INTEGER_32 -- How many items satisfying exp are in Current? ensure current_set_unchanged: Current ~ old Current.deep_twin maximum_result: Result <= count comprehension alias "|" (exp: PREDICATE [G]): like Current -- Largest subset of the current set whose elements satisfy exp -- e.g. for set: MSL_SET[STRING], -- (set | agent {STRING}.has_substring ("xy")) = {g:set | g.has_substring("xy")} ensure current_set_unchanged: Current ~ old Current.deep_twin is_subset: Result |<: Current all_satisfying_exp: Result.hold_count (exp) = # Result consistent_satisfying_items: Current.hold_count (exp) = # Result feature -- Equality is_equal (other: like Current): BOOLEAN -- Is curren set equal to 'other'? ensure then Result = (Current |<: other and then other |<: Current) feature -- Debug output debug_output: STRING_8 -- String that should be displayed in debugger to represent Current. out: STRING_8 -- New string containing terse printable representation -- of current object invariant imp.object_comparison no_duplicates: across imp.Lower |..| imp.upper as i all across imp.Lower |..| imp.upper as j all imp [i.item] ~ imp [j.item] implies i.item = j.item end end end -- class SET
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