Re: issue LOAD-TIME-EVAL, version 11

[sandra%defun@cs.utah.edu (Sandra J Loosemore)]

> Date: Sun, 19 Mar 89 22:18:17 CST
> From: alarson@src.honeywell.com (Aaron Larson)
> 
> My argument has been something like
> "The identity of the conses that make up a program shouldn't be significant
> to the value of the program".  Proposal **3 sort of shoots down that
> argument.  

The objection that was raised to proposal **2 was that the notion of
"references" to LOAD-TIME-VALUE forms was not well-defined.  The one
example that was raised that bothered me the most was something like

  (flet ((foo () (load-time-value (bar))))
    (declare (inline foo))
    (list (foo) (foo)))

Intuitively, there's only one reference to the LOAD-TIME-VALUE
expression, but if the compiler does the obvious transformation to
code FOO inline, you've suddenly got two references.

Basically, what proposal **3 does is avoid this whole problem by
putting the burden on programmers to be very careful about potential
sharing of LOAD-TIME-VALUE expressions.  (It's really only a problem
for ones that are non-read-only.) There are some of us who feel kind
of uncomfortable about this, but it seemed like trying to come up with
a formal definition of what a unique reference to a LOAD-TIME-VALUE
form meant would open up an even bigger can of worms.

-Sandra
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