Re: EVAL-WHEN

[Guy Steele <gls@THINK-AQUINAS.ARPA>]

    Date: 4 Apr 1986 09:35-EST
    From: NGALL@G.BBN.COM
	
	Date: Thu 3 Apr 86 22:52:12-EST
	From: "Rodney A. Brooks" <BROOKS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
    
	    Doesn't 
	    (setf (symbol-function 'foo) (COPY '(LAMBDA  ...)))
	    guarantee to produce a function definition not compiled by compiling the
	    file.  If (setf (symbol-function 'foo) ...) compiles, then all bets are
	    off.
    
	There is no requirement in CLtL that it be legal for a symbol function
	cell to contain a lambda expression. In some implementations this
	will cause an error when such a symbol is used in the function
	position of an eval-ed expression. These implementations place a closure
	in symbol function cells for interpreted functions, which all point
	to the same compiled code sequence which takes a literal from the
	closure (the literal is the lambda expression) and does the right
	call into the middle of the interpreter. 
		
    This should definitely be pointed out on page 90.  Also, exactly what objects
    may be the value in a setf of (symbol-function <<symbol>>) should be clarified.

I would contend that any Lisp object may be the value in a setf of
(symbol-function <symbol>), and that a subsequent invocation of
(symbol-function <symbol>) should retrieve exactly that object (or one
EQL to it).  However, this does not prevent implementations from
wrapping that object in a closure internally on storing and unwrapping
it again on fetching.
--Guy