define and set! with multiple-values

[Jonathan Bachrach <Jonathan.Bachrach@ircam.fr>]

I propose to extend `set!' and `define' to allow accomodate
multiple-values.  The syntax would be:

  (set! place-1 place-2 ... new-value) => new-value

which could be translated into:

  (bind ((tmp-1 tmp-2 ... new-value))
    (set! place-1 tmp-1)	
    (set! place-2 tmp-2)	
    ...
    (values tmp-1 tmp-2 ...))

an example would be:

  ? (set! x y (location window))
  10
  20
  ?

Along these lines I also propose to extend define to accomodate
multiple-values as follows

  (define variable-name-1 variable-name-2 ... initial-value) =>
    (values variable-name-1 variable-name-2 ...)

Of course I propose to allow variable-name-k to include a type
declaration as in:

  ? (define (x <integer>) (y <integer>) (location window))
  x
  y
  ?

This extension is completely backward compatible with the current
Dylan specification.

-- jonathan bachrach

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