[Axiom-developer] Continuations in SPAD

[Ralf Hemmecke]

> Ralf Hemmecke <address@hidden> writes:
> > Could you demonstrate some SPAD-code-to-be which uses continuations
> >  and solves a problem that cannot be solved easily by an Aldor 
> > equivalent?
>
> I am not to sure what you want me to give. Writing a lot of pseudo 
> code is not terribly useful in all cases.

No not pseudo code. Define a syntax for continuations in SPAD-to-be. And 
then write real SPAD-to-be code.

> Knuth wrote in TAOCP in section 1.4.2 "It is rather difficult to find
> short, simple examples of coroutines that illustrate the importance
> of the idea; the most useful coroutine applications are generally
> quite lengthy".

Of course, if Knuth says it, coroutines are important. ;-)

> Now, coroutines are a generalization of generators,
> and continuations are a generalization of coroutines.  I am having a
> though time thinking about a useful, simple, example.  I could give
> an example of how continuations could be used to implement generators
> which would likely be short and perhaps informative -- is that what
> you are looking for?

Actually not, but maybe it would be illustrative anyway.

I am looking for something that would cause me headaches to implement in 
(current) Aldor and which would be easy with continuations. Is must be 
related to implementing mathematics. I don't yet see how useful 
continuations are in a mathematical library context.

You mentioned parallel execution, but there is also
http://www.inf.ethz.ch/personal/mannhart/piit/
http://www.ph.ed.ac.uk/~bj/paraldor/WWW/


> > Do you think that SPAD-continuations are important for implementing
> >  mathematical algorithms? Examples?

> Well, I think Tim already gave a better list than I could off the top
>  of my head:
>
> http://lists.gnu.org/archive/html/axiom-developer/2007-07/msg00169.html

I've read that already and it did not yet convince me. I want to see 
real algebra code that looks natural to implement by means of continuations.


Ralf