note description: "RELATION data structure for both specification and implementation." author: "JSO and JW" date: "$Date$" revision: "$Revision$" class REL [G -> attached ANY, H -> attached ANY] create make_empty, make_from_tuple_array convert make_from_tuple_array ({attached ARRAY [TUPLE [G, H]]}) feature {NONE} -- Initialization default_create -- Process instances of classes with no creation clause. -- (Default: do nothing.) -- (from ANY) do end feature -- Access generating_type: TYPE [detachable REL [G, H]] -- Type of current object -- (type of which it is a direct instance) -- (from ANY) external "built_in" ensure -- from ANY generating_type_not_void: Result /= Void end generator: STRING_8 -- Name of current object's generating class -- (base class of the type of which it is a direct instance) -- (from ANY) external "built_in" ensure -- from ANY generator_not_void: Result /= Void generator_not_empty: not Result.is_empty end feature -- Comparison frozen deep_equal (a: detachable ANY; b: like arg #1): BOOLEAN -- Are a and b either both void -- or attached to isomorphic object structures? -- (from ANY) do if a = Void then Result := b = Void else Result := b /= Void and then a.is_deep_equal (b) end ensure -- from ANY instance_free: class shallow_implies_deep: standard_equal (a, b) implies Result both_or_none_void: (a = Void) implies (Result = (b = Void)) same_type: (Result and (a /= Void)) implies (b /= Void and then a.same_type (b)) symmetric: Result implies deep_equal (b, a) end frozen equal (a: detachable ANY; b: like arg #1): BOOLEAN -- Are a and b either both void or attached -- to objects considered equal? -- (from ANY) do if a = Void then Result := b = Void else Result := b /= Void and then a.is_equal (b) end ensure -- from ANY instance_free: class definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.is_equal (b)) end frozen is_deep_equal (other: REL [G, H]): BOOLEAN -- Are Current and other attached to isomorphic object structures? -- (from ANY) require -- from ANY other_not_void: other /= Void external "built_in" ensure -- from ANY shallow_implies_deep: standard_is_equal (other) implies Result same_type: Result implies same_type (other) symmetric: Result implies other.is_deep_equal (Current) end frozen standard_equal (a: detachable ANY; b: like arg #1): BOOLEAN -- Are a and b either both void or attached to -- field-by-field identical objects of the same type? -- Always uses default object comparison criterion. -- (from ANY) do if a = Void then Result := b = Void else Result := b /= Void and then a.standard_is_equal (b) end ensure -- from ANY instance_free: class definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.standard_is_equal (b)) end frozen standard_is_equal (other: REL [G, H]): BOOLEAN -- Is other attached to an object of the same type -- as current object, and field-by-field identical to it? -- (from ANY) require -- from ANY other_not_void: other /= Void external "built_in" ensure -- from ANY same_type: Result implies same_type (other) symmetric: Result implies other.standard_is_equal (Current) end feature -- Status report conforms_to (other: ANY): BOOLEAN -- Does type of current object conform to type -- of other (as per Eiffel: The Language, chapter 13)? -- (from ANY) require -- from ANY other_not_void: other /= Void external "built_in" end same_type (other: ANY): BOOLEAN -- Is type of current object identical to type of other? -- (from ANY) require -- from ANY other_not_void: other /= Void external "built_in" ensure -- from ANY definition: Result = (conforms_to (other) and other.conforms_to (Current)) end feature -- Duplication frozen clone (other: detachable ANY): like other obsolete "Use `twin' instead. [2017-05-31]" -- Void if other is void; otherwise new object -- equal to other -- -- For non-void other, clone calls copy; -- to change copying/cloning semantics, redefine copy. -- (from ANY) do if other /= Void then Result := other.twin end ensure -- from ANY instance_free: class equal: Result ~ other end copy (other: REL [G, H]) -- Update current object using fields of object attached -- to other, so as to yield equal objects. -- (from ANY) require -- from ANY other_not_void: other /= Void type_identity: same_type (other) external "built_in" ensure -- from ANY is_equal: Current ~ other end frozen deep_clone (other: detachable ANY): like other obsolete "Use `deep_twin' instead. [2017-05-31]" -- Void if other is void: otherwise, new object structure -- recursively duplicated from the one attached to other -- (from ANY) do if other /= Void then Result := other.deep_twin end ensure -- from ANY instance_free: class deep_equal: deep_equal (other, Result) end frozen deep_copy (other: REL [G, H]) -- Effect equivalent to that of: -- copy (other . deep_twin) -- (from ANY) require -- from ANY other_not_void: other /= Void do copy (other.deep_twin) ensure -- from ANY deep_equal: deep_equal (Current, other) end frozen deep_twin: REL [G, H] -- New object structure recursively duplicated from Current. -- (from ANY) external "built_in" ensure -- from ANY deep_twin_not_void: Result /= Void deep_equal: deep_equal (Current, Result) end frozen standard_clone (other: detachable ANY): like other obsolete "Use `standard_twin' instead. [2017-05-31]" -- Void if other is void; otherwise new object -- field-by-field identical to other. -- Always uses default copying semantics. -- (from ANY) do if other /= Void then Result := other.standard_twin end ensure -- from ANY instance_free: class equal: standard_equal (Result, other) end frozen standard_copy (other: REL [G, H]) -- Copy every field of other onto corresponding field -- of current object. -- (from ANY) require -- from ANY other_not_void: other /= Void type_identity: same_type (other) external "built_in" ensure -- from ANY is_standard_equal: standard_is_equal (other) end frozen standard_twin: REL [G, H] -- New object field-by-field identical to other. -- Always uses default copying semantics. -- (from ANY) external "built_in" ensure -- from ANY standard_twin_not_void: Result /= Void equal: standard_equal (Result, Current) end frozen twin: REL [G, H] -- New object equal to Current -- twin calls copy; to change copying/twinning semantics, redefine copy. -- (from ANY) external "built_in" ensure -- from ANY twin_not_void: Result /= Void is_equal: Result ~ Current end feature -- Basic operations frozen as_attached: attached REL [G, H] obsolete "Remove calls to this feature. [2017-05-31]" -- Attached version of Current. -- (Can be used during transitional period to convert -- non-void-safe classes to void-safe ones.) -- (from ANY) do Result := Current end frozen default: detachable REL [G, H] -- Default value of object's type -- (from ANY) do end frozen default_pointer: POINTER -- Default value of type POINTER -- (Avoid the need to write p.default for -- some p of type POINTER.) -- (from ANY) do ensure -- from ANY instance_free: class end default_rescue -- Process exception for routines with no Rescue clause. -- (Default: do nothing.) -- (from ANY) do end frozen do_nothing -- Execute a null action. -- (from ANY) do ensure -- from ANY instance_free: class end feature {SET} -- Implementation imp: ARRAYED_LIST [PAIR [G, H]] -- (from SET) item_imp: detachable CELL [PAIR [G, H]] -- (from SET) set_imp (other_imp: like imp) -- (from SET) do imp := other_imp if not imp.object_comparison then imp.compare_objects end end Void_item -- (from SET) once item_imp := Void end feature -- Agent functions in_domain (g: G; dom: SET [G]): BOOLEAN do if dom.has (g) then Result := True end end in_range (h: H; ran: SET [H]): BOOLEAN do if ran.has (h) then Result := True end end singleton_g (g: G): SET [G] do create Result.make_from_array (<<g>>) ensure # Result = 1 Result.has (g) end singleton_gh (g: G; h: H): REL [G, H] do create Result.make_from_tuple_array (<<[g, h]>>) ensure # Result = 1 end singleton_h (h: H): SET [H] do create Result.make_from_array (<<h>>) ensure # Result = 1 Result.has (h) end feature -- Commands for implementation difference (other: REL [G, H]) -- Subtract the current set by 'other'. -- (from SET) do across other as it loop subtract (it.item) end Void_item ensure -- from SET definition: old Current.deep_twin ~ Current |\/| (old Current.deep_twin |/\| other) end extend (g: PAIR [G, H]) -- Extend the current set by 'g'. -- (from SET) do if not has (g) then imp.extend (g) end Void_item ensure -- from SET 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 end intersect (other: REL [G, H]) -- Intersect current set with 'other'. -- (from SET) do from imp.start until imp.after loop if not other.has (imp.item) then imp.remove else imp.forth end end Void_item ensure -- from SET Current |<: old Current.deep_twin Current |<: other definition: hold_count (agent in_both_set (?, old Current.deep_twin, other)) = count end subtract (g: PAIR [G, H]) -- Subtract the current set by 'g'. -- (from SET) do from imp.start until imp.after loop if imp.item ~ g then imp.remove else imp.forth end end Void_item ensure -- from SET 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 end union (other: REL [G, H]) -- Extend the current set by 'other'. -- (from SET) do across other as it loop extend (it.item) end Void_item ensure -- from SET old Current.deep_twin |<: Current other |<: Current definition: hold_count (agent in_either_set (?, old Current.deep_twin, other)) = count end feature -- Commands for relational operations domain_restrict (ds: SET [G]) -- Keep all pairs whose first values are members of 'ds'. do domain_subtract (domain |\ ds) ensure new_rel_is_a_subset: Current |<: (old Current.deep_twin) only_ds_in_new_rel: ((old Current.deep_twin) |\ (Current)).domain ~ (old Current.deep_twin.domain |\ ds) end domain_restrict_by (g: G) -- Keep pairs whose first values are 'd'. do domain_subtract (domain - g) ensure new_rel_is_a_subset: Current |<: (old Current.deep_twin) only_g_in_new_rel: ((old Current.deep_twin) |\ (Current)).domain ~ (old Current.deep_twin.domain |\ singleton_g (g)) end domain_subtract (ds: SET [G]) -- Subtract all pairs whose first values are members of 'ds'. local g: G do from imp.start until imp.after loop g := imp.item.first if ds.has (g) then imp.remove else imp.forth end end ensure new_rel_is_a_subset: Current |<: (old Current.deep_twin) no_ds_in_new_rel: ((old Current.deep_twin) |\ (Current)).domain ~ ds.comprehension (agent in_domain (?, (old Current.deep_twin).domain)) end domain_subtract_by (g: G) -- Subtract pairs whose first values are 'g'. do domain_subtract (create {SET [G]}.make_from_array (<<g>>)) ensure new_rel_is_a_subset: Current |<: (old Current.deep_twin) no_g_in_new_rel: ((old Current.deep_twin) |\ (Current)).domain ~ singleton_g (g).comprehension (agent in_domain (?, (old Current.deep_twin).domain)) end override (r: like Current) -- Update current relation such that it aggres on 'r'. do domain_subtract (r.domain) union (r) ensure Current ~ ((old Current.deep_twin |<< r.domain) |\/| r) end override_by (t: TUPLE [g: G; h: H]) -- Update current relation such that it aggres on 'g |-> h'. do domain_subtract_by (t.g) extend (create {PAIR [G, H]}.make_from_tuple (t)) ensure Current ~ ((old Current.deep_twin @<< t.g) |\/| singleton_gh (t.g, t.h)) end range_restrict (rs: SET [H]) -- Keep all pairs whose second values are members of 'rs'. do range_subtract (range |\ rs) ensure new_rel_is_a_subset: Current |<: (old Current.deep_twin) only_rs_in_new_rel: ((old Current.deep_twin) |\ (Current)).range ~ (old Current.deep_twin.range |\ rs) end range_restrict_by (h: H) -- Keep all pairs whose second values are 'h'. do range_subtract (range |\ singleton_h (h)) ensure new_rel_is_a_subset: Current |<: (old Current.deep_twin) only_h_in_new_rel: ((old Current.deep_twin) |\ (Current)).range ~ (old Current.deep_twin.range |\ singleton_h (h)) end range_subtract (rs: SET [H]) -- Subtract all pairs whose second values are members of 'rs'. local h: H do from imp.start until imp.after loop h := imp.item.second if rs.has (h) then imp.remove else imp.forth end end ensure new_rel_is_a_subset: Current |<: (old Current.deep_twin) no_rs_in_new_rel: ((old Current.deep_twin) |\ (Current)).range ~ rs.comprehension (agent in_range (?, (old Current.deep_twin).range)) end range_subtract_by (h: H) -- Subtract pairs whose second values are 'h'. do range_subtract (create {SET [H]}.make_from_array (<<h>>)) ensure new_rel_is_a_subset: Current |<: (old Current.deep_twin) no_h_in_new_rel: ((old Current.deep_twin) |\ (Current)).range ~ singleton_h (h).comprehension (agent in_range (?, (old Current.deep_twin).range)) end feature -- Constructor make_empty -- Initialize an empty set. -- (from SET) do create imp.make (0) imp.compare_objects ensure -- from SET is_empty end make_from_array (a: ARRAY [PAIR [G, H]]) -- (from SET) do make_empty across a as it loop extend (it.item) end imp.compare_objects ensure -- from SET 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 end make_from_tuple_array (a: ARRAY [TUPLE [fst: G; snd: H]]) do make_empty across a as tup loop extend (create {PAIR [G, H]}.make_from_tuple (tup.item)) end end make_one (a_singleton: PAIR [G, H]) -- make a singleton set -- (from SET) do make_empty extend (a_singleton) ensure -- from SET count = 1 has (a_singleton) end feature -- Conversion to array. as_array: ARRAY [TUPLE [G, H]] do create Result.make_empty across Current as c loop Result.force (c.item.as_tuple, Result.upper + 1) end Result.compare_objects ensure Current ~ create {REL [G, H]}.make_from_tuple_array (Result) 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 set_as_array: ARRAY [PAIR [G, H]] -- (from SET) do create Result.make_from_array (imp.to_array) Result.compare_objects end feature -- Debug output debug_output: STRING_8 -- String that should be displayed in debugger to represent Current. -- (from SET) do Result := out ensure -- from DEBUG_OUTPUT result_not_void: Result /= Void end out: STRING_8 -- New string containing terse printable representation -- of current object -- (from SET) local i: INTEGER_32 do create Result.make_empty Result.append ("{ ") from i := imp.Lower until i > imp.upper loop check attached {PAIR [G, H]} imp [i] as e then Result.append (e.out) end if i < imp.upper then Result.append (", ") end i := i + 1 end Result.append (" }") ensure -- from ANY out_not_void: Result /= Void end feature -- Equality is_equal (other: REL [G, H]): BOOLEAN -- Is curren set equal to 'other'? -- (from SET) require -- from ANY other_not_void: other /= Void do Result := # Current = # other and then other |<: Current and then Current |<: other ensure -- from ANY symmetric: Result implies other ~ Current consistent: standard_is_equal (other) implies Result ensure then -- from SET Result = (Current |<: other and then other |<: Current) end feature -- Iteration new_cursor: ITERATION_CURSOR [PAIR [G, H]] -- Fresh cursor associated with current structure -- (from SET) do Result := imp.new_cursor ensure -- from ITERABLE result_attached: Result /= Void end feature -- Output Io: STD_FILES -- Handle to standard file setup -- (from ANY) once create Result Result.set_output_default ensure -- from ANY instance_free: class io_not_void: Result /= Void end print (o: detachable ANY) -- Write terse external representation of o -- on standard output. -- (from ANY) do if o /= Void then Io.put_string (o.out) end ensure -- from ANY instance_free: class end frozen tagged_out: STRING_8 -- New string containing terse printable representation -- of current object -- (from ANY) external "built_in" ensure -- from ANY tagged_out_not_void: Result /= Void end feature -- Platform Operating_environment: OPERATING_ENVIRONMENT -- Objects available from the operating system -- (from ANY) once create Result ensure -- from ANY instance_free: class operating_environment_not_void: Result /= Void end feature -- Quantifiers comprehension alias "|" (exp: PREDICATE [PAIR [G, H]]): REL [G, H] -- 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")} -- (from SET) local i: INTEGER_32 imp_item: PAIR [G, H] do create Result.make_empty from i := imp.Lower until i > imp.upper loop imp_item := imp [i] if exp.item ([imp_item]) then Result.extend (imp_item) end i := i + 1 end Result.Void_item ensure -- from SET 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 end hold_count (exp: PREDICATE [PAIR [G, H]]): INTEGER_32 -- How many items satisfying exp are in Current? -- (from SET) local i: INTEGER_32 do from i := imp.Lower until i > imp.upper loop if exp.item ([imp [i]]) then Result := Result + 1 end i := i + 1 end ensure -- from SET current_set_unchanged: Current ~ old Current.deep_twin maximum_result: Result <= count end feature -- Queries for relational operations domain_restricted alias "|<" (ds: SET [G]): like Current -- Return a copy of current relation with -- all pairs whose first values are members of 'ds' kept. do Result := Current.deep_twin Result.domain_restrict (ds) ensure current_rel_unchanged: Current ~ old Current.deep_twin new_rel_is_a_subset: Result |<: Current only_ds_in_new_rel: (Current |\ Result).domain ~ (domain |\ ds) end domain_restricted_by alias "@<" (g: G): like Current -- Return a copy of current relation with -- all pairs whose first values are 'g' kept. do Result := Current.deep_twin Result.domain_restrict_by (g) ensure current_rel_unchanged: Current ~ old Current.deep_twin new_rel_is_a_subset: Result |<: Current only_g_in_new_rel: (Current |\ Result).domain ~ (domain |\ singleton_g (g)) end domain_subtracted alias "|<<" (ds: SET [G]): like Current -- Return a new copy of current relation with -- all pairs whose first values are members of 'ds' subtracted. do Result := Current.deep_twin Result.domain_subtract (ds) ensure current_rel_unchanged: Current ~ old Current.deep_twin new_rel_is_a_subset: Result |<: Current no_ds_in_new_rel: (Current |\ Result).domain ~ ds.comprehension (agent in_domain (?, domain)) end domain_subtracted_by alias "@<<" (g: G): like Current -- Return a new copy of current relation with -- all pairs whose first values 'g' subtracted. do Result := Current.deep_twin Result.domain_subtract_by (g) ensure current_rel_unchanged: Current ~ old Current.deep_twin new_rel_is_a_subset: Result |<: Current no_ds_in_new_rel: (Current |\ Result).domain ~ singleton_g (g).comprehension (agent in_domain (?, domain)) end image alias "[]" (g: G): SET [H] -- Retrieve the set of items that are associated with 'g'. do create Result.make_empty across Current as c loop if c.item.first ~ g then Result.extend (c.item.second) end end ensure current_rel_unchanged: Current ~ old Current.deep_twin Result.is_empty implies not domain.has (g) across Result as r all has (create {PAIR [G, H]}.make_from_tuple ([g, r.item])) end across range.differenced (Result) as r all not has (create {PAIR [G, H]}.make_from_tuple ([g, r.item])) end end inverse: REL [H, G] do create Result.make_empty across Current as pair loop Result.extend (create {PAIR [H, G]}.make_from_tuple ([pair.item.second, pair.item.first])) end ensure current_rel_unchanged: Current ~ old Current.deep_twin Result.inverse.is_equal (Current) end overriden alias "|<+" (r: like Current): like Current -- Return a copy of current relation that agrres on 'r'. do Result := Current.deep_twin Result.override (r) ensure current_rel_unchanged: Current ~ old Current.deep_twin Result ~ ((Current |<< r.domain) |\/| r) end overriden_by alias "@<+" (t: TUPLE [g: G; h: H]): like Current -- Return a copy of current relation that agrres on 'g |-> h'. do Result := Current.deep_twin Result.override_by (t.g, t.h) ensure current_rel_unchanged: Current ~ old Current.deep_twin Result ~ ((Current @<< t.g) |\/| singleton_gh (t.g, t.h)) end range_restricted alias "|>" (rs: SET [H]): like Current -- Return a copy of current relation with -- all pairs whose second values are members of 'rs' kept. do Result := Current.deep_twin Result.range_restrict (rs) ensure current_rel_unchanged: Current ~ old Current.deep_twin new_rel_is_a_subset: Result |<: Current only_rs_in_new_rel: (Current |\ Result).range ~ (range |\ rs) end range_restricted_by alias "@>" (h: H): like Current -- Return a copy of current relation with -- all pairs whose second values are 'h' kept. do Result := Current.deep_twin Result.range_restrict_by (h) ensure current_rel_unchanged: Current ~ old Current.deep_twin new_rel_is_a_subset: Result |<: Current only_h_in_new_rel: (Current |\ Result).range ~ (range |\ singleton_h (h)) end range_subtracted alias "|>>" (rs: SET [H]): like Current -- Return a new copy of current relation with -- all pairs whose second values are members of 'ds' subtracted. do Result := Current.deep_twin Result.range_subtract (rs) ensure current_rel_unchanged: Current ~ old Current.deep_twin new_rel_is_a_subset: Result |<: Current no_rs_in_new_rel: (Current |\ Result).range ~ rs.comprehension (agent in_range (?, range)) end range_subtracted_by alias "@>>" (h: H): like Current -- Return a new copy of current relation with -- all pairs whose second values are 'h' subtracted. do Result := Current.deep_twin Result.range_subtract_by (h) ensure current_rel_unchanged: Current ~ old Current.deep_twin new_rel_is_a_subset: Result |<: Current no_rs_in_new_rel: (Current |\ Result).range ~ singleton_h (h).comprehension (agent in_range (?, range)) end feature -- Queries for specification. count alias "#": INTEGER_32 -- Return the cardinality of the set. -- (from SET) do Result := imp.count ensure -- from SET current_set_unchanged: Current ~ old Current.deep_twin definition: Result = hold_count (agent g_to_true) end differenced alias "|\" (other: REL [G, H]): REL [G, H] -- Return a new set representing the difference between Current and 'other'. -- (from SET) local new_imp: ARRAYED_LIST [PAIR [G, H]] do create new_imp.make (0) across imp as src loop if not other.has (src.item) then new_imp.extend (src.item) end end create Result.make_empty Result.set_imp (new_imp) Result.Void_item ensure -- from SET current_set_unchanged: Current ~ old Current.deep_twin definition: Current ~ Result |\/| (Current |/\| other) end extended alias "+" (g: PAIR [G, H]): REL [G, H] -- Return a new set representing the addtion of current and 'g'. -- (from SET) do create Result.make_empty Result.set_imp (Current.imp.twin) Result.extend (g) Result.Void_item ensure -- from SET 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 end has (g: PAIR [G, H]): BOOLEAN -- Does the set contain 'g'? -- (from SET) do Result := (imp.has (g)) ensure -- from SET 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 end intersected alias "|/\|" (other: REL [G, H]): REL [G, H] -- Return a new set representing the intersection of current and 'other'. -- (from SET) do create Result.make_empty across other as it loop if has (it.item) then Result.extend (it.item) end end Result.Void_item ensure -- from SET 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 end is_empty: BOOLEAN -- Is the set empty? -- (from SET) do Result := (count = 0) ensure -- from SET current_set_unchanged: Current ~ old Current.deep_twin Result = (# Current = 0) end is_subset_of alias "|<:" (other: REL [G, H]): BOOLEAN -- (from SET) local i: INTEGER_32 do from Result := True i := imp.Lower until not Result or else i > imp.upper loop Result := other.has (imp [i]) i := i + 1 end ensure -- from SET current_set_unchanged: Current ~ old Current.deep_twin Result = across Current as cur all other.has (cur.item) end end subtracted alias "-" (g: PAIR [G, H]): REL [G, H] -- Return a new set representing the difference between Current and 'other'. -- (from SET) do create Result.make_empty Result.set_imp (Current.imp.twin) Result.subtract (g) Result.Void_item ensure -- from SET 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 end unioned alias "|\/|" (other: REL [G, H]): REL [G, H] -- Return a new set representing the union of current and 'other'. -- (from SET) do create Result.make_empty Result.set_imp (Current.imp.twin) across other as it loop Result.extend (it.item) end Result.Void_item ensure -- from SET 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 end feature -- Query and command for arbitrary set members choose_item -- Choose an arbitrary element of the -- set and store it in item -- (from SET) require -- from SET not is_empty do create item_imp.put (imp [count]) ensure -- from SET has (item) chosen end chosen: BOOLEAN -- (from SET) do Result := attached item_imp end item: PAIR [G, H] -- Return an arbitrary member from the set. -- (from SET) require -- from SET not is_empty chosen do check attached item_imp as l_item then Result := l_item.item end ensure -- from SET has (Result) end remove_item -- Remove an arbitrary member (i.e., 'item') from the set. -- (from SET) require -- from SET not is_empty chosen do imp.go_i_th (count) imp.remove item_imp := Void ensure -- from SET Current ~ old Current.deep_twin - old item not chosen end feature {NONE} -- Retrieval frozen internal_correct_mismatch -- Called from runtime to perform a proper dynamic dispatch on correct_mismatch -- from MISMATCH_CORRECTOR. -- (from ANY) local l_msg: STRING_8 l_exc: EXCEPTIONS do if attached {MISMATCH_CORRECTOR} Current as l_corrector then l_corrector.correct_mismatch else create l_msg.make_from_string ("Mismatch: ") create l_exc l_msg.append (generating_type.name) l_exc.raise_retrieval_exception (l_msg) end end feature -- Status queries domain: SET [G] -- Return the domain set of relation. do create Result.make_empty across Current as c loop Result.extend (c.item.first) end end is_function: BOOLEAN -- Is current relation a function? -- i.e., each domain value maps to at most one value. local c: ITERATION_CURSOR [PAIR [G, H]] do from Result := True c := new_cursor until not Result or else c.after loop if # image (c.item.first) > 1 then Result := False end c.forth end ensure Result = across domain as d all # image (d.item) = 1 end end is_injection: BOOLEAN -- Is current relation an injective function? -- i.e., no two domain values map to the same range vaule. do Result := is_function and then inverse.is_function ensure Result = (is_function and inverse.is_function) end range: SET [H] -- Return the range set of relation. do create Result.make_empty across Current as c loop Result.extend (c.item.second) end end feature {SET} -- agent functions eq (v1, v2: PAIR [G, H]): BOOLEAN -- (from SET) do Result := v1 ~ v2 end g_to_true (v: PAIR [G, H]): BOOLEAN -- (from SET) do Result := True ensure -- from SET definition: Result end in_both_set (g: PAIR [G, H]; s1, s2: SET [PAIR [G, H]]): BOOLEAN -- (from SET) do Result := s1.has (g) and then s2.has (g) end in_either_set (g: PAIR [G, H]; s1, s2: SET [PAIR [G, H]]): BOOLEAN -- (from SET) do Result := s1.has (g) or else s2.has (g) end invariant -- from SET 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 -- from ANY reflexive_equality: standard_is_equal (Current) reflexive_conformance: conforms_to (Current) end -- class REL
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