Re: [patch] First round (request for discussion)

[Marius Vollmer]

Daniel Skarda <address@hidden> writes:

> > However, making vectors and strings and maybe all kinds of stuff
> > into getters and setters is certainly appealing, but I'm not sure
> > whether it is a good idea in general.
> 
>  Yes. Using getters/setters makes scheme written for Guile less
> portable, moreover setters/getters can make scheme sources code a
> little bit obfuscated and hard to maintain.

I'm leaning towards not allowing getters/setters on all container
types.  It somehow feels wrong to me.  On the other hand, it also
feels somewhat natural.

>  On the other hand adding setter/getter feature to guile is quite
> cheap (and imho clean) and sometimes it can be useful.

Maybe we could avoid hard coding it into the core and introduce a
bad-procedure hook.  Ideally, that hook would be a generic function
(and setter would also be a generic function).  Let's say we have a
generic function `apply-object' that is used to invoke every object,
including procedure.  We could then add getters for strings like so:

    (define-method (call-object (s <string>) index)
      (string-ref s index))

This can be made efficient (for the usual cases) in the same way as
`+' has been made into a generic function.

> > I think `apply-setter' should be provided in addition to `setter'.
> 
>   Initially I wanted to extend only `setter' - but that is not
> possible. As you can see in my patch `setter' does not handle all
> types as apply-setter does.  The main reason for this incompleteness
> is the need for additional function (setter-type) or an extension to
> `setter'.
> 
>   (set! (m a1 a2) v)
> 
>     "expands" to
> 
>        ((setter m) m a1 a2 v)           ;;; m is smob with setter

The setter for smobs could be defined as a closure, I think:

    (define (get-smob-setter obj)
      (lambda args
        (apply apply-setter obj args)))

`apply-setter' would not need to explicitly construct this closure,
and it is OK when `set!' expands into a call to `apply-setter'.

>    * Implement getters for GOOPS objects? (I guess I should consult that with
>      Mikael Djurfeldt.

You can already make classes that can be invoked.  Use
<operator-class> as a meta-class.  Don't know about setters...