Re: DECLARE SPECIAL Considered Confusing

[Jeff Dalton <jeff%aiva.edinburgh.ac.uk@Cs.Ucl.AC.UK>]

   Date: Mon, 7 Jul 86 10:03 EDT
   From: "David C. Plummer" <DCP@arpa.scrc-quabbin>
   Subject: DECLARE SPECIAL Considered Confusing
   
       Date: 5 Jul 86 16:54 PDT
       From: Pavel.pa@Xerox.COM
   
       What do people think?  It would appear that some implementations already
       work this way.
   
   I agree.  Consider LET to be a macro that turns into LAMBDA:
      (let ((foo (1+ foo)))
        (declare (special foo))
        foo)
      => ((lambda (foo)
            (declare (special foo))
            foo)
          (1+ foo))
   [I think this is what MacLisp actually did (does?).]  The scoping here
   is clear: the foo in (1+ foo) is outside the scope of the declaration.
   
If the SPECIAL declaration is to apply to the init forms, LET can be
a macro that turns into two lambdas:

	(let ((foo (1+ foo))) (declare (special foo)) foo)
	 => ((lambda ()
	      (declare (special foo))
	      ((lambda (foo) foo) (declare (special foo)) (1+ foo))))

Some implementations do work this way.