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From: "Bin Chen" <chenbin@cs.umass.edu>
Newsgroups: comp.lang.ada
Subject: Help: Problem with JGnat
Date: Thu, 1 Aug 2002 22:46:38 -0400
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Date: 2002-08-01T22:46:38-04:00
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Hi,

I used jgnat compile the following Ada program to Java bytecode, it was OK,
but when I ran the .class file, it always threw the following exception.
Could you give me any feedback?

Thank you.

Bin Chen


Exception:

Exception in thread "main" java.lang.IllegalMonitorStateException
        at
jgnat.adalib.system$task_primitives$operations.write_lock__2(s-taprop.adb:22
9)
        at
jgnat.adalib.system$task_primitives$operations.lock_all_tasks_list(s-taprop.
adb:771)
        at
jgnat.adalib.system$task_primitives$operations.enter_task(s-taprop.adb:373)
        at
jgnat.adalib.system$task_primitives$operations.initialize(s-taprop.adb:834)
        at jgnat.adalib.system$tasking._elabb(s-taskin.adb:186)
        at ada_main.adainit(b~main.adb:89)
        at main.main(main.adb)

Sources:

--Pack_Factorial.ads
package Pack_Factorial is
  task type Task_Factorial is --Specification
    entry Start( F:in Positive ); --Rendezvous
    entry Finish( Result:out Positive ); --Rendezvous
  end Task_Factorial;
end Pack_Factorial;

--Pack_Factorial.adb
package body Pack_Factorial is
  task body Task_Factorial is --Implementation
    Factorial : Positive;
    Answer : Positive := 1;
  begin
    accept Start( F:in Positive ) do --Factorial
      Factorial := F;
    end Start;
    for I in 2 .. Factorial loop --Calculate
      Answer := Answer * I;
    end loop;
    accept Finish( Result:out Positive ) do --Return answer
      Result := Answer;
    end Finish;
  end Task_Factorial;
end Pack_Factorial;

--main.adb
with Ada.Text_Io, Ada.Integer_Text_Io, Pack_Factorial;
use Ada.Text_Io, Ada.Integer_Text_Io, Pack_Factorial;
procedure main is
 Thread_1 : Task_Factorial;
 Factorial: Positive;
begin
 Thread_1.Start(5); --Start factorial calculation
 Put("Factorial 5 is ");
 Thread_1.Finish( Factorial ); --Obtain result
 Put( Factorial ); New_Line;
end Main;