Re: Subverting 'Access for Sub-programs

[Brian Rogoff <bpr@shell5.ba.best.com>]

On Tue, 3 Aug 1999, Anton Gibbs wrote:

> Dear Ada Community,
> 
> Can someone please advise me on the best way to subvert the language
> rules that prevent the use of 'Access on a locally declared procedure ?

I'm looking forward to a week where this question is asked every day :-). 

> For normal objects it is possible to use 'Unchecked_Access but for
> sub-programs this is not allowed.
> 
> "Why does this idiot want to do this ?" I hear you ask.

Not at all. Any idiot who has ever used Pascal can do this, as can any
idiotic user of a functional programming language, though, to be fair, the 
FPers pay for that in general with garbage collection. 

If you use GNAT, Unrestricted_Access does what you want. You have
suggested generic contortions, others suggest hauling the offending
function up to library level, and then offer excuses as to why Ada has 
this big wart, sometimes even justifying the wart by arguing that these 
contortions are a good idea. Robert Dewar explains the "why" of the
access rules in his post, and the reason for the fondness for displays
over static links goes back to the requirements for Ada 83. Another
workaround is to use tagged types,  but since you can't extend them
locally either it isn't often too helpful. 

The consolation here is that neither C++ nor Java even have nested
functions. 

-- Brian