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just a question
Date: Thu, 3 Dec 87 11:05:13 -0200
From: Moshe Cohen <firstname.lastname@example.org>
Why is it not possible to set an array element to the result of
the COMPILE function as in:
(SETF (AREF ARRAY-NAME 1) (COMPILE NIL #'(LAMBDA () 'F))) .
The following error message is received:
Trap: The argument given to the CAR instruction,
#<LEXICAL-CLOSURE (LAMBDA NIL #) 40303466>,
was not a locative, a list, or NIL.
It IS possible to do it with an auxiliary variable to hold the
result or by using what I understand as a NOOP:
(SETF (AREF ARRAY-NAME 1) (EVAL '(COMPILE NIL #'(LAMBDA () 'F))))
Use ' instead of #'. The second argument to COMPILE is supposed to be a
lambda-expression, not a lexical closure. The SETF form expands into a
LET, so in the first case the interpreter must create a lexical closure
for the #'(lambda...). In the second case this isn't necessary because
EVAL defaults to the null lexical environment, so in that case
#'(lambda...) is equivalent to '(lambda...).