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Newsgroups: comp.lang.ada
Date: Fri, 9 Aug 2013 10:09:58 -0700 (PDT)
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Subject: Re: 4 beginner's questions on the PL Ada
From: Adam Beneschan <adambeneschan@aol.com>
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Xref: news.eternal-september.org comp.lang.ada:16722
Date: 2013-08-09T10:09:58-07:00
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On Friday, August 9, 2013 9:50:53 AM UTC-7, Emanuel Berg wrote:
> 1. How do you make a constant in Ada? Can I make one that is
> computed, for example an integer, set to Milliseconds(something)?

   Some_Constant : constant integer :=3D <expression>.  The expression can =
be any expression that can be computed.

=20
> 2. How do you get options from the CL? I.e., how do you do the C=20
> argv in Ada?

Ada.Command_Line.  http://www.ada-auth.org/standards/12rm/html/RM-A-15.html

=20
> 3. Is it possible to get the task *name* (from the code) into a=20
> string, programatically? That way, a generic procedure could be
> used to communicate from tasks, with Put_Line, and without having
> to hard code the task name every time.

No, not really.  One thing to keep in mind is that Ada has task *types*, so=
 that you can declare a task type and then start any number of tasks of tha=
t type.  And the tasks don't have to be associated with variables; you can =
start an array of tasks:

   type Task_Array is array (1 .. 10) of Task_Type;
   T : Task_Array;

will start 10 tasks, and they won't really have names.  Well, I guess you c=
an call them T(1), T(2), ...  But tasks can also be record components, and =
you can have accesses to tasks, so there really isn't a concept of a "name"=
 for a task.  So if you want to give tasks a name, you'll have to do this i=
n the program.


> 4. How do you exit Ada altogether? For example, if there are 3=20
> tasks, and one solves the problem, how can I terminate the whole
> application at once? (Rather than sending messages to all the
> tasks, "OK, we're done looking!")

I don't recommend having one task kill the entire program.  Ada allows you =
to define types that have finalization procedures associated with them (e.g=
. for a file, you might want a finalization procedure that makes sure any r=
emaining data is flushed to the file).  Ada makes sure that when a procedur=
e or task is exited, anything that needs to be finalized will be finalized.=
  Performing an operation that just exits the program suddenly will subvert=
 that.  There's an "abort" statement to allow one task to terminate other t=
asks; that *does* ensure that finalization takes place.  But overall, I thi=
nk it's better to do things cleanly; one way is to send a message to the ot=
her tasks with entry calls, but you can also create a variable (or a protec=
ted object) that's accessible to all tasks that they can check at certain p=
oints to see if they can quit.

                               -- Adam