Do symbols need to be EQ?

[Alessio Stalla]

Package = map from symbol name to symbol object.
INTERN ~= (or (gethash ...) (setf (gethash ...)))
UNINTERN ~= remhash

There's nothing special about symbols. You'd get the same effect with a map
of constants and operations to add/remove them from the map.

On Fri, Jul 3, 2015 at 10:56 AM, Kenneth Tilton <ken at tiltontec.com> wrote:

>
>
> On Fri, Jul 3, 2015 at 4:48 AM, Edi Weitz <edi at weitz.de> wrote:
>
>> Perhaps the excerpt below (from a fresh LW image) makes more obvious
>> what my "philosophical problem" is.  I have redacted the output of
>> DISASSEMBLE to only show the relevant parts.  It shows that EQ is
>> essentially just one simple comparison with a machine word (which is
>> what I expected).  It also shows that I get the same machine word
>> again as long as I don't mess around with UINTERN or something.  But
>> once I've done that, I get _another_ machine word and so in terms of
>> simple-minded EQ I get a different object.
>>
>> CL-USER 1 > (defun foo-1 (x)
>>               (eq x 'bar))
>> FOO-1
>> CL-USER 2 > (disassemble 'foo-1)
>>       ;; ...
>>       21:      3DF771F921       cmp   eax, 21F971F7    ; BAR
>>       26:      750D             jne   L3
>>       ;; ...
>> NIL
>> CL-USER 3 > (defun foo-2 (x)
>>               (eq x 'bar))
>> FOO-2
>> CL-USER 4 > (disassemble 'foo-2)
>>       ;; ...
>>       21:      3DF771F921       cmp   eax, 21F971F7    ; BAR
>>       26:      750D             jne   L3
>>       ;; ...
>> NIL
>> CL-USER 5 > (unintern 'bar)
>> T
>> CL-USER 6 > (defun foo-3 (x)
>>               (eq x 'bar))
>> FOO-3
>> CL-USER 7 > (disassemble 'foo-3)
>>       ;; ...
>>       21:      3DAB71F921       cmp   eax, 21F971AB    ; BAR
>>       26:      750D             jne   L3
>>       ;; ...
>> NIL
>>
>>
> Sorry, where is the problem? The spec is clear that a new object (with a
> new pointer) will be created given the unintern hijinx, so all is
> consistent: different pointer, EQ->nil.
>
> ie, It is not just "in terms of EQ" that you have a different object: you
> have created two distinct pointer objects (and EQ dutifully says so).
>
> And at a higher level of abstraction, you have created two different
> symbols, one interned and one not.
>
> -kt
>
> --
> Kenneth Tilton
> 54 Isle of Venice Dr
> Fort Lauderdale, FL 33301
>
> ken at tiltontec.com
> http://tiltontec.com
> @tiltonsalgebra
>
> 646-269-1077
>
> "In a class by itself." *-Macworld*
>
>
>
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