Why does plant1 keep being NIL?
Please, could someone explain me why "make-array" has 开发者_开发问答no effect on plant1?
(LET (plant1) ((setq plant1 (make-array '(4 4))) (print plant1) (setf (AREF PLANT1 0 0) 1)))
NIL Error: Attempt to do an array operation on NIL which is not an array. [condition type: TYPE-ERROR]
(LET (plant1) ((setq plant1 (make-array '(4 4))) (print plant1) (setf (AREF PLANT1 0 0) 1)))
First rule: format your code.
(LET (plant1)
((setq plant1 (make-array '(4 4)))
(print plant1)
(setf (AREF PLANT1 0 0) 1)))
There are too many parentheses. The syntax of let has a body of code, which is a sequence of forms. You have parentheses around the sequence, which is wrong. Read the Common Lisp HyperSpec entry for LET. It mentions the syntax.
Use:
(LET (plant1)
(setq plant1 (make-array '(4 4)))
(print plant1)
(setf (AREF PLANT1 0 0) 1))
Which is the same as:
(LET ((plant1 (make-array '(4 4))))
(print plant1)
(setf (AREF PLANT1 0 0) 1))
Take this with a grain of salt, because I mainly deal with Scheme, not Common Lisp.
Let uses the following syntax:
(let ((var1 2) (var2 7)) (+ var1 var2))
If you only want to define one variable...
(let ((var1 2)) ...);;Replace ... with whatever operations you do in that scope.
From what I can tell, you never defined plant1 in the let, plus the syntax is wrong, so once you try to do sets, it doesn't work. Of course, I could be totally wrong, so only use this as something to try until someone who knows what they're talking about chimes in.
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