Do symbols need to be EQ?
Edi Weitz
edi at weitz.de
Fri Jul 3 08:48:42 UTC 2015
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
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