Re: Unifying properties

[Marius Vollmer <mvo at zagadka dot ping dot de>]

Mikael Djurfeldt <mdj@mdj.nada.kth.se> writes:

> Speaking as the originator of all current properties except symbol
> properties:
> 
>   I don't think properties belong in Guile at all.
> 
> Properties don't have lexical scope.  They don't respect module
> boundaries.  They are not thread safe.  They are essentially a relic
> of old programming techniques.

These are good points.  I think that something like properties could
be useful, but I find that I use dedicated hash-tables anyway.

So, we should probably design some helper functions for doing the job
of properties, but in a more modern way.  What about:

  Function: make-object-property

    Return a new `procedure with setter' P that can be used to attach
    a property to objects.  When calling P as

        (set! (P obj) val)

    where `obj' is any kind of object, it attaches `val' to `obj' in
    such a way that it can be retrieved by calling P as

        (P obj)

This makes it harder to see all properties of an object, but it is
unlikely that properties carry all interesting information about an
object anyway.

Behind the scenes, make-object-property could use a highly tuned
hashing scheme to maybe be even more efficient than the normal
properties that we now have.