Re : [Chicken-users] hacking the mailbox egg

[minh thu]

> On Jan 7, 2007, at 10:14 AM, minh thu wrote:
>
> > Hi,
> >
> > I'd like to write a small library along the lines of the mailbox egg.
> > The goal is to have a queue where the elements are ordered by some
> > kind of value attached to them (in my case, it will be the moment when
> > the element has to be extracted from the queue).
>
> So essentially a priority queue.
Exactly, just forgot the name...

> >
> > Reading the code, and being fairly new to scheme and chicken, I have
> > some questions:
> >
> > - why is there a queue.scm file ? Is it because usage of the extras
> > unit can be disabled ?
>
> No. Because the extras unit doesn't disable interrupts. Mailbox
> doesn't synchronize access to its globals explicitly but disables
> interrupts, so the entire file is a critical-section.
Does that mean that when a file disables interrupts, when calling code
from another unit, it could be interrupted ?

So using a (disable-interrupts) declaration is a bit like making all
methods of a java class synchronised ?

> > - what are those ##sys#xxx and ##core#xxx functions ?
> >  is it permitted (good style) to use them ? where are they
> > documented ?
>
> Permitted, yes.
>
> Good style? Well, I wouldn't use them unless necessary, or unless
> hacking in someone else's code that does use them. You may notice
> that 'queue.scm' defines wrappers around the '##sys' access routines
> so the main body of the code calls very few directly. And some
> operations are just not available outside of the sys namespace, in
> which case they must be used.
>
> Documented, no.
Thanks, but, what are they ? What can I use instead of ##sys#slot ? In
the present case, is it ok to use them ?

> >
> > When/if I complete the writing of such a library, would it be good to
> > add it to Eggs Unlimited ?
> > Have you an idea for its name ? ordered-mailbox ?
>
> Sure.

Ok, thanks !
mt