Re: difficulty of writing translators

[Per Bothner <bothner@cygnus.com>]

> However, it would please me (if it's not too deadly to implement) to
> see functions allowed to return set!-able references:

>    (set! (my-prop) 17)
>    (my-prop)             => 17

Kawa supports this (for some primitive functions - I haven't decided
yet how to define such functions in Scheme).

Note that having functions "return set!-able references" is
probably not the way to do it, since we want a normal call (not in a
set! context) to return plain value, not a reference.  Instead,
we allow functions to have "attributes", and one attribute is a
functions setter function.  Then we define:
	(set! (f . args) value)
as being syntactic sugar for:
	((setter f) value . args)

> (While I'm at it, I'd argue for (set! (array-ref a 6) 'zork) etc. as a
> clean alternative to setf.)

The advantage of this design is that it is procedural, while
setf is macro-based.  Hence setf only works for setter functions
explicitly known (by name) at compile time, but setter works on
procedure *values* at run-time, and is therefore much more in
the spirit of Scheme.

	--Per Bothner
Cygnus Solutions     bothner@cygnus.com     http://www.cygnus.com/~bothner