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Re: (eq #'eq #'eq) (reply to Jeff Dalton)
- To: "Steve Bacher (Batchman)" <@sail.stanford.edu:SEB1525@draper.com>, firstname.lastname@example.org
- Subject: Re: (eq #'eq #'eq) (reply to Jeff Dalton)
- From: Jeff Dalton <jeff%aiai.edinburgh.ac.uk@NSS.Cs.Ucl.AC.UK>
- Date: Sat, 17 Sep 88 16:41:31 BST
- In-reply-to: Steve Bacher (Batchman)'s message of Fri, 16 Sep 88 14:07 EDT
> If SYMBOL-FUNCTION "returns the autoloader function", then (eq f #'eq)
> ...actually, this works out, but very peculiarly.
It is not even slightly peculiar. (SYMBOL-FUNCTION 'F) returns
whatever it returns. Presumably it does this consistently. There are
two main cases: (1) F does not need to be autoloaded, and (2) F does
need to be loaded. The second case then has two subcases: (2a)
SYMBOL-FUNCTION causes the autoload to happen, or else (2b) it returns
the autoloader function.
Suppose F does not need to be autoloaded. Then SYMBOL-FUNCTION
returns the function value of F. If you call it again, it returns
that very same object (the function value) again. So these two
results are F. Now suppose F needs to be autoloaded. Either
calling SYMBOL-FUNCTION on F causes the autoloading to take place,
and we are in the same situation as above, or else it does not cause
the autoloading to take place but instead returns a function object
that, if called, will autoload F. Again, if you call SYMBOL-FUNCTION
again it will presumably behave in the same way and return the very
same <call me and I'll autoload F> function object. Again the
results are EQ.
Since this argument is independent of choice of F, it applies when
F is the symbol EQ.
> I still don't consider this fortuitous setup to justify your point,
It is not a fortuitous setup. Access functions (such as SYMBOL-
FUNCTION) return objects. Object identity can be tested with EQ.
Of course, you might say that SYMBOL-FUNCTION isn't a simple access
function. Perhaps it's not like SYMBOL-VALUE at all. Perhaps it
always makes a new function object. If we take this line, then I
am saying that SYMBOL-FUNCTION should change to be like SYMBOL-
VALUE. Again, this is neither peciliar nor fortuitous: it is just
a question of how SYMBOL-FUNCTION should behave.
> Autoloading isn't the only rationale in any case. Consider
> a system with multiple copies of the same function (perhaps liked into
> several modules, or compiler-generated as quasi-inline minisubrs, or
I don't really know what you have in mind here, so I'm probably going
to miss the point. I don't, for example, know what you mean by "the
same". If "same" means EQ, then they aren't copies. And I'm talking
only of #'F. This has different from cases like (F...), where F
might be compiled in-line.