[cdr-discuss] What about CDR 3, then?

[Pascal Costanza]

On 23 Nov 2006, at 21:53, Christophe Rhodes wrote:

> Hi,
>
> I have plans to modify CDR 3 slightly, adding a non-portable test case
> to the Test Case section and improving the references.  I appreciate
> that the issue that CDR 3 describes is largely theoretical, but are
> there any comments from anyone out there?  Getting any feedback before
> the finalization date would obviously be useful; it may be a
> theoretical issue at the moment but I hope that it will become a
> practical issue in the not-distant future.

[I am posting this as a regular Common Lisper, not as a CDR editor.]

I have just read your proposal and the respective original  
CONCATENATE-SEQUENCE issue in the HyperSpec.

Apart from the fact that I have a hard time imagining what other  
interesting implementations one could have for sequences with fixed  
length apart from lists and vectors, I also have a hard time to  
imagine how sequences with non-fixed lengths could be integrated, for  
example with concatenate-sequence.

To be more concrete: You could regard lazy lists and streams as kinds  
of sequences, and they could indeed be made subtypes of 'sequence. In  
those cases, though, it doesn't make a lot of sense that concatenate- 
sequence supports them, for example, especially when they model  
infinite sequences (like "all prime numbers", or so).

I think a different way to say this is as the following question:  
What guarantees do the existing sequence functions give us? For  
example, do they have to terminate?

What other kinds of subtypes of sequence do you have in mind?


Pascal
-- 
Pascal Costanza, mailto:pc at p-cos.net, http://p-cos.net
Vrije Universiteit Brussel, Programming Technology Lab
Pleinlaan 2, B-1050 Brussel, Belgium