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-- ===============================================================================================================
-- Tray in tray allocation for a sortation system
-- By José Antonio Esparza and Kim Bjerge - spring 2010
-- ===============================================================================================================
class Tray
types
public State = <Empty> | <Full>;
public UID = nat
inv u == u <= TrayAllocator`NumOfTrays; -- Limitation on UID
values
public TraySize : nat1 = 600 -- Size of any tray mm
instance variables
-- It is allowed for a tray to be <Full> with no item associated
-- in this case an unknown item is detected by the card reader
state : State := <Empty>;
item : [Item] := nil;
-- If an item is associated with a tray the state must be <Full>
inv item <> nil => state = <Full>;
id : UID; -- Tray UID
operations
-- Tray constructor
public Tray: UID ==> Tray
Tray(i) ==
(
id := i;
);
-- Return tray id
pure public GetId: () ==> nat
GetId() ==
return id;
-- Returns true if tray is empty
pure public IsTrayEmpty: () ==> bool
IsTrayEmpty () ==
return state = <Empty>;
-- Returns true if tray is full
pure public IsTrayFull: () ==> bool
IsTrayFull () ==
return state = <Full>;
-- Returns item on tray
pure public GetItem: () ==> [Item]
GetItem () ==
return item;
-- Set state of tray
public SetState: State ==> ()
SetState (s) ==
(
if s = <Empty>
then -- Remove item if tray is empty
item := nil;
state := s;
);
-- Returns state of tray ==> <empty> or <full>
public GetState: () ==> State
GetState () ==
return state;
-- Puts an item on the tray and creates association between tray and item
public ItemOnTray: Item ==> ()
ItemOnTray (i) ==
(
atomic -- Only needed if item is assigned before state
(
item := i;
state := <Full>;
);
item.AssignItemToTray(self);
IO`print("-> Item id " ^ String`NatToStr(item.GetId()) ^
"size " ^ String`NatToStr(item.GetSize()) ^
"on tray id " ^ String`NatToStr(id) ^ "\n");
)
pre state = <Empty> and item = nil;
functions
sync
--thread
traces
end Tray
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