The ParaSail Programming Language

import Clock;
interface Dining_Philosophers<Num_Phils : Univ_Integer := 5; Context<>> is
 func Dinner_Party (Length_Of_Party : Clock::Interval_Type; Context);
 type Philosopher_Index is new Integer<1..Num_Phils>;
 type Left_Or_Right is Enum<[#is_left_fork, #is_right_fork]>;
 concurrent interface Fork<> is 
 func Pick_Up_Fork(queued var F : Fork; Which_Fork : Left_Or_Right);
 func Put_Down_Fork(locked var F : Fork);
 func Create(Index : Philosopher_Index) -> Fork;
 end interface Fork;
 type Fork_Array is Array<Fork, Indexed_By => Philosopher_Index>;
 
end interface Dining_Philosophers;
class Dining_Philosophers<Num_Phils : Univ_Integer := 5; Context<>> is
 exports
 func Dinner_Party(Length_Of_Party : Clock::Interval_Type; Context) is
 Delay(Context.Clock.Wall_Clock, Length_Of_Party);
 Display(Context.IO.Standard_Output, "Dinner Party is over\n");
 return; 
 ||
 var Forks : Fork_Array := [for I in 1..Num_Phils => Create(I)];
 
 for Phil in Philosopher_Index concurrent loop
 const Left_Fork := Phil;
 const Right_Fork := Phil mod Num_Phils + 1;
 
 while True loop
 Display(Context.IO.Standard_Output, "Philosopher " | Phil | " is thinking\n");
 Delay(Clock, Next(Context.Random)); // Think
 then
 Pick_Up_Fork(Forks[Left_Fork], #is_left_fork);
 ||
 Pick_Up_Fork(Forks[Right_Fork], #is_right_fork);
 then
 Display(Context.IO.Standard_Output, "Philosopher " | Phil | " is eating\n");
 Delay(Clock, Next(Context.Random)); // Eat
 then
 Put_Down_Fork(Forks[Left_Fork]);
 ||
 Put_Down_Fork(Forks[Right_Fork]);
 end loop;
 end loop;
 end func Dinner_Party;
 
 concurrent class Fork<> is
 var Is_Available : Boolean;
 
 exports
 func Create(Index : Philosopher_Index) -> Fork is
 return (Is_Available => True);
 end func Create;
 
 func Pick_Up_Fork (queued var F : Fork; Which_Fork : Left_Or_Right) is 
 queued until F.Is_Available then
 F.Is_Available := False;
 end func Pick_Up_Fork; 
 
 func Put_Down_Fork(locked var F : Fork) is
 F.Is_Available := True;
 end func Put_Down_Fork;
 
 end class Fork;
end class Dining_Philosophers;

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