Re: The Prob class

[Joe Neeman]

On Thu, 2009-08-20 at 23:38 +0100, Trevor Daniels wrote:
> I'm trying to complete the 'prob' entry in the Technical glossary. 
> From a position of ignorance I've come up with this:
> 
> "PRoperty OBjects, or @strong{probs} for short, are instances of
> the @code{Prob} class, a simple base class for objects which have
> mutable and immutable property alists.  The @code{Music} class
> derives from @code{Prob}.  Instances of the @code{Prob} class are
> also created to hold the formatted content of system grobs and
> titling blocks during page layout."
> 
> Is this correct, accurate, complete?
> 
> As an aside, why does the Grob class not derive from Prob?

Properties of Grobs have extra functionality: you can set any grob
property to be a callback function, in which case the callback will be
evaluated transparently the first time you try to read that property.
Probs don't support that (I'm not sure why not).

Also, I think there are issues with doing inheritance properly on types
that are exposed to scheme. There were some discussions in that
direction regarding Pitch and Pitchclass.

Joe