Re: Proposal: Auto-allocation of Indefinite Objects

[Brian Drummond <brian@shapes.demon.co.uk>]

On Mon, 27 Jul 2020 00:47:30 -0700, Yannick Moy wrote:

>> My proposal is that it should (sometimes?) be possible to declare
>> objects of indefinite types such as String and have the compiler
>> automatically declare the space for them without the programmer having
>> to resort to access types.

In one sense we already have this ... in that we can do this in a Declare 
block, where stack allocation is a practical implementation.

But what about cases where (for whatever reason) we want it allocated on 
the heap?

In another sense we have it as JP Rosen said, for the specific example 
Unbounded_String.

Is there any way we could generalise the (storage, access and lifetime 
aspects of) Unbounded_String for unconstrained arrays and discriminated 
records in such a way that Unbounded_String can be a simple instantiation 
of one of these? 

But without the full flexibility (or overhead) of controlled types. So, 
somewhere in between, as:

1. Controlled type
|
---2.Unconstrained Array or Discriminated Record 
   |
   ---3. Unbounded String (instance of 2)

2) can be implemented internally using pointers, but externally appears 
to be a data object, just like Unbounded_String does, with similar 
semantics. 

-- Brian