Re: DYNAMIC ADA TASK CREATION?

["Robert I. Eachus" <rieachus@attbi.com>]

I wrote:
>>  There are times when a programmer will create an object type that 
>>contains tasks.  And he may want to use, say, a container package for 
>>objects of this type. (Yes, most container libraries refuse to work with 
>>limited data objects, but not all.)

Matthew Heaney wrote:
> The new release of the Charles library does indeed work with element
> types that are limited.  The basic idea is that when you insert an
> element into the container, the element is allocated with its default
> value -- whatever that means for the element type.  For example, for
> an element type that is controlled, controlled initialization will
> occur.

Not quite what I had in mind, but great.  I was thinking of container 
packages that manage references/access values, assuming that the 
original objects cannot be moved or changed.  When I need a package like 
this, I usually encapsulate a "normal" container library around a 
limited type and an explicit access type:

    generic
      type Element is limited private;
      type Pointer is access Element;
    package Limited_Stack is
      procedure Push(E: in Element);
      procedure Push(P: in Pointer);
      function Peek return Pointer;
      function Pop return Pointer;
      function Pop return Element; -- constant view...
    end Limited_Stack;

The explicit access type is because of the rules on return by reference 
providing a constant view.  I may propose as an Ada 0Y revision allowing 
return by reference functions where a view conversion would be allowed. 
  In other words, you could have a return by reference function as an in 
out parameter in another call.  It seems that should be part of AI-318, 
but AI-318 goes a lot further without addressing this at all. An 
alternative would be allowing a function to return an anonymous access type.