Re: Newbie: Task parametering

[Poul-Erik Andreasen <poulerik@pea.dk>]

jimmaureenrogers@worldnet.att.net wrote:
> Andrew Price wrote:
> 
>>Hello all,
>>
>>I need to initialise some tasks with a few parameters when I instantiate
>>them. After looking at
>>http://www.adaic.com/docs/95style/html/sec_6/6-1-3.html it seems the
>>best way to do this is using an access type discriminant to pass a
>>record to the tasks.
>>
>>With that in mind, I created this record type;
>>
>>type Task_Data is
>>       record
>>       Name : aliased String(1..8);
>>       Period : aliased Duration;
>>       Repetitions : aliased Integer;
>>    end record;
>>
>>
>>and then in the main part of my program I use it like this;
>>
>>    type Task_Handle is access A_Task;  -- used to point to the task
>>    Another_Task : Task_Handle;
>>    type Data_Handle is access Task_Data; -- used to point to its data
>>    Data_For_Task : Data_Handle;
>>
>>begin  -- The main prog will now spawn three of the above tasks
>>
>>    -- Parameterise the first task and then start it.
>>    Data_For_Task := new Task_Data;
>>    Data_For_Task.Name := "Task A  ";
>>    Data_For_Task.Period := 0.5;
>>    Data_For_Task.Repetitions := 5;
>>    Another_Task := new A_Task(Data_For_Task);
>>
>>So while this approach works, I can't help but feel that I'm going about
>>this in a 'long winded' way (especially coming from a mostly C background).
>>
>>Is there are neater way of putting the data into the Task_Data records?
>>Or is there an better approach to the whole task parameterisation I
>>should consider?
>>
>>Now is probably a good time to add the disclaimer that this is part of a
>>lab work exercise for a course I'm currently undertaking at university.
> 
> 
> There is a little roblem with your approach.
> 
> It does not actually initialize the task. The task begins running
> before the values are set. You are likely to encounter a race
> condition with your approach.


Where do you get that idea. Before any allocation the access_varible 
only contain null;


PEA