bag_incl.sa


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-- Author: Benedict A. Gomes <gomes@samosa.ICSI.Berkeley.EDU>


partial class RO_BAG_INCL{ETP}

partial class RO_BAG_INCL{ETP} is -- Partial class that for the read only bag abstraction, class -- $RO_BAG{ETP}. For more information on the relationship between -- the abstract classes, partial classes and actual implementations -- please see the class comment class in the abstraction. -- RTP is the return type of various operations in this bag -- abstraction -- -- This partial class implements some of the operations required by -- the abstraction in terms of a set of core functions which are -- stubs in this partial class. These stubs must be replaced by -- real function in any descendant that actually implements the -- abstraction. Particular implementations may replace also some of -- the non-stub operations by substantially more efficient -- versions, that make use of properties of the actual -- implementation. -- include COMPARE{ETP}; -- -- Stubs -- stub count(arg:ETP):INT; -- Return the number of occurences of 'arg' in the container stub add(e:ETP):SAME; stub delete(e:ETP):SAME; stub delete_all(e:ETP):SAME; stub copy:SAME; stub elt!: ETP; stub size:INT; stub has(e:ETP):BOOL; -- -- Methods not required by the $RO_BAG abstraction. They can be safely -- redefined away, if not needed stub create:SAME; create(arg:$ELT{ETP}):SAME is -- Create a new bag out of the elements of 'arg' res: SAME := #; loop res := res.add(arg.elt!) end; return res; end; create(arg:ARRAY{ETP}):SAME is -- Create a new bag from the elements of the array 'arg' -- The reason for having a separate routine in this case is to -- permit type inference to be used so that a user may write -- a:BAG{INT} := #(|1,2,3|); res: SAME := #; loop res := res.add(arg.elt!) end; return res; end; -- -- Methods required by the $RO_BAG abstraction -- n_unique:INT is -- Return the number of unique elements res:INT := 0; loop discard ::= unique!; res := res+1; end; return res; end; is_subset_of(arg:$RO_BAG{ETP}):BOOL is -- Returns true if 'self' is a subset of 'arg'. For elements that occur -- multiple times, the number of occurences of the element in 'arg' -- must be greater than or equal to the number of occurences in self -- -- result=true iff for all e in self: count(e) <= arg.count(e) loop e ::= elt!; if count(e) > arg.count(e) then return false; end; end; return true; end; concat(arg:$ELT{ETP}):SAME is -- Returns a bag containing all the elements of self and 'arg'. -- For elements that occur multiple times, the result contains -- the sum of the number of occurences in self and 'arg' -- -- result=bag of all e s.t. result.count(e)=self.count(e)+arg.count(e)>0 res ::= copy; loop res := res.add(arg.elt!); end; return res; end; union(arg: $RO_BAG{ETP}):SAME is -- Returns a bag containing the elements of 'self' and 'arg'. -- For elements that occur multiple times, the result contains -- the maximum number of occurences in either self or 'arg' -- This definition permits the union of sets to be consistent -- with the union of bags. -- -- result=bag of all e s.t. -- result.count(e)= max(self.count(e),arg.count(e)) > 0 res ::= copy; loop arg_elt:ETP := arg.elt!; if ~res.has(arg_elt) then res := res.add(arg_elt); else if arg.count(arg_elt) > res.count(arg_elt) then res := res.add(arg_elt); end; end; end; return res end; intersection(arg: $RO_BAG{ETP}):SAME is -- Returns a bag containing the elements common to self and 'arg' -- For elements that occur multiple times, the result contains -- the minimum number of occurrences in either self or 'arg' -- -- result=bag of all e s.t. -- result.count(e)=min(self.count(e),arg.count(e)) > 0 res ::= copy; loop e ::= unique!; num_to_delete: INT := (count(e) - arg.count(e)); if num_to_delete > 0 then loop num_to_delete.times!; res := res.delete(e); end; end; end; return res end; -- For the $CONTAINER abstraction is_empty:BOOL is -- Return true if the size = 0. return size = 0; end; equals(c:$RO_BAG{ETP}):BOOL is -- Return true if self.value = c.value if size /= c.size then return false end; loop e:ETP := c.unique!; if count(e) /= c.count(e) then return false end; end; return true; end; as_array:ARRAY{ETP} is -- Return the elements of the container as an array res ::= #ARRAY{ETP}(size); loop res.set!(elt!) end; return res; end; str: STR is return ELT_ALG{ETP}::str(self); end; -- Return a string representation of self end;

partial class BAG_INCL{ETP}

partial class BAG_INCL{ETP} is -- Partial class that for the bag abstraction, class $BAG{ETP}. -- For more information on the relationship between the abstract -- classes, partial classes and actual implementations please see -- the class comment class in the abstraction. -- -- This partial class implements some of the operations required by -- the abstraction in terms of a set of core functions which are -- stubs in this partial class. These stubs must be replaced by -- real function in any descendant that actually implements the -- abstraction. Particular implementations may replace also some of -- the non-stub operations by substantially more efficient -- versions, that make use of properties of the actual -- implementation. include RO_BAG_INCL{ETP}; stub count(e:ETP):INT; stub add(e:ETP); stub delete(e:ETP); stub delete_all(e:ETP); stub copy:SAME; stub elt!: ETP; stub size:INT; stub has(e:ETP):BOOL; -- -- Methods not required by the $BAG abstraction -- create(arg:$ELT{ETP}):SAME is -- Create a new bag out of the elements of 'arg' res: SAME := #; loop res := res.add(arg.elt!) end; return res; end; -- -- Methods required by the $BAG abstraction -- as_value:VBAG{ETP} is return #VBAG{ETP}(self) end; -- Return the value associated with this reference to a set clear post size = 0 is -- Delete all elements of self f:ARRAY{ETP} := #(n_unique); loop f.set!(unique!); end; loop delete_all(f.elt!); end; end; -- Implementation note: with the following routines, care must be -- taken to ensure that the collection being iterated over is not -- being modified at the same time. Thus it is best to always -- iterate over 'arg', since self is being modified to_concat(arg:$ELT{ETP}) is -- Concatenate the elemetns of 'arg' to this bag -- self <- initial(self).add_bag(arg) loop add(arg.elt!); end; end; to_union(arg: $RO_BAG{ETP}) is -- Turn this bag into the union of self and 'arg' -- self <- initial(self).union(arg) loop arg_elt:ETP := arg.elt!; if ~has(arg_elt) then add(arg_elt); else if arg.count(arg_elt) > count(arg_elt) then add(arg_elt); end; end; end; end; to_intersection(arg:$RO_BAG{ETP}) is -- Turn this bag into the intersection of self and 'arg' -- self <- initial(self).intersection(arg) -- Copy the unique elts so that we don't iterate while -- deleting f ::= #ARRAY{ETP}(n_unique); loop f.set!(unique!) end; loop e ::= f.elt!; if ~arg.has(e) then delete_all(e); end; end; -- For elements in the intersection, reduce the number -- of repetitions to the min number of occurences loop e ::= arg.unique!; num_to_delete:INT := count(e) - arg.count(e); if num_to_delete > 0 then loop num_to_delete.times!; delete(e); end; end; end; end; add(e:ETP):SAME is -- Result is a new bag containing all the elements of self and 'e' res:SAME := copy; res.add(e); return res; end; delete(e:ETP):SAME is -- Result is a new bag containing all the elements of self except for -- an element equal to 'e', if one exists. If more than one element -- is equal to 'e', delete only one of them res:SAME := copy; res.delete(e); return res; end; delete_all(e:ETP):SAME is -- Result is a new bag containing all the elements of self except for -- any elements equal to 'e' res:SAME := copy; res.delete_all(e); return res; end; end;