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-- File: PCollection_HQueue.cdl
-- Created: Wed Feb 10 18:03:38 1993
-- Author: Mireille MERCIEN
-- <mip@sdsun4>
---Copyright: Matra Datavision 1991
generic class HQueue from PCollection (Item as Storable)
inherits Persistent
---Purpose: A queue is a sequence of items in which items
-- are added at one end (called the back of the
-- queue) and removed at the other end (called
-- the front)
-- The Queue is empty if there are no elements.
raises NoSuchObject from Standard
class QueueNode instantiates HSingleList from PCollection(Item);
class QueueIterator from PCollection
---Purpose: Iterator of the class Queue.
raises NoMoreObject from Standard,
NoSuchObject from Standard
is
Create(Q : HQueue from PCollection)
returns QueueIterator from PCollection;
---Purpose: Creates an iterator on the queue Q.
-- Sets the iterator at the beginning of the Queue Q.
More(me) returns Boolean from Standard;
---Level: Public
---Purpose: Returns True if there are other items.
Next(me: in out) raises NoMoreObject from Standard;
---Level: Public
---Purpose: Sets the iterator to the next item.
Value(me) returns any Item raises NoSuchObject from Standard;
---Level: Public
---Purpose: Returns the item value corresponding to
-- the current position of the iterator.
fields
TheIterator : QueueNode;
end;
is
Create returns mutable HQueue from PCollection;
---Purpose: Creates an empty queue.
Length(me) returns Integer from Standard;
---Level: Public
---Purpose: Returns the number of items in the queue.
---Example: before
-- me = (A B C)
-- returns 3
IsEmpty(me) returns Boolean from Standard;
---Level: Public
---Purpose: Returns True if the queue contains no element.
Front(me) returns any Item raises NoSuchObject from Standard;
---Level: Public
---Purpose: Returns the item at the front of the queue.
-- Raises an exception if the queue is empty.
---Example: before
-- me = (A B C)
-- after
-- me = (A B C)
-- returns
-- A
FFront(me) returns QueueNode;
---Level: Public
---Purpose: Returns the field TheFront(the front of the queue).
FBack(me) returns QueueNode;
---Level: Public
---Purpose: Returns the field Theback(the back of the queue).
Clear(me : mutable);
---Level: Public
---Purpose: Removes all the elements from the queue
---Example: before
-- me = (A B C)
-- after
-- me = ()
Push(me : mutable; T : Item);
---Level: Public
---Purpose: Inserts an item at the back of the queue.
---Example: before
-- me = (A B) , T = C
-- after
-- me = (A B C)
Pop(me : mutable) raises NoSuchObject from Standard;
---Level: Public
---Purpose: Removes an item from the front of the queue.
-- Raises an exception if the queue is empty
---Example: before
-- me = (A B C)
-- after
-- me = (B C)
-- returns
-- A
ChangeFront(me:mutable ; T : Item) raises NoSuchObject from Standard;
---Level: Public
---Purpose: Replaces the front element of the queue with T.
-- Raises an exception if the queue is empty.
---Example: before
-- me = (A B C) , T = D
-- after
-- me = (D B C)
ShallowCopy(me)
returns mutable like me
is redefined;
---Level: Advanced
---C++: function call
ShallowDump (me; s: in out OStream)
is redefined;
---Level: Advanced
---C++: function call
Destroy(me : mutable);
---C++: alias ~
fields
TheFront : QueueNode;
TheBack : QueueNode;
TheLength : Integer from Standard;
end;
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