Re: access to controlled types

["Terry J. Westley" <twestley@buffalo.veridian.com>]

>"Terry J. Westley" <twestley@buffalo.veridian.com> writes:
>
>> In a new version of TASH, I've implmented an interface
>> to Tcl objects (which are reference counted) with Ada
>> controlled types.  I've been very impressed with how
>> well this works in GNAT.
>>
>> But, there are certain calls in the interface which
>> return an access to a class-wide type.  It's easy to
>> reference count these newly created objects, but since
>> the access type is not controlled, the reference counts
>> don't get decremented.  What's the solution?  Should I
>> declare another controlled type which *contains* an
>> access to the original controlled type?  Or, is there
>> a better solution?
>

Stephen Leake <Stephen.Leake@gsfc.nasa.gov> responds:
>Perhaps the functions that return a class-wide access type should
>simply be removed. Do they serve a real purpose in the system? Is
>there another (safer) way to satisfy that need? I guess the latter is
>what you are suggesting. But often, a function that violates an
>abstraction truly does not belong.

You have a good point.  I'll think about it a bit.  The specific
situation is that TASH supports Tcl lists which are heterogenous.

So, when you fetch an element out of the list, it could be an
integer, a float, a string, or another list.

Other functions that return an element of the list are Head and Tail.

--
Terry J. Westley, Principal Engineer
Veridian Engineering, Calspan Operations
twestley@buffalo.veridian.com   http://www.veridian.com/
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Author of TASH, an Ada binding to Tcl/Tk.
Visit the TASH web site at http://tash.calspan.com.
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