Re: Use of a counter in a list

Modifying constants, such as quoted lists, such as '(0), is undefined 
behavior.

Do (let ((a (list 0)) ...) instead.

W dniu 2024-05-14 11:29, steph.tougard via Sbcl-help napisał(a):

> Hi,
> 
> I don't understand why this code does not work with SBCL while it works 
> perfectly with ABCL and CLISP
> 
> (let ((a '(0)))
> (defun inc-a () (incf (car a)))   (defun a () (car a)))
> 
> On SBCL
> 
> CL-USER> (a)
> 0 (0 bits, #x0, #o0, #b0)
> CL-USER> (inc-a)
> 1 (1 bit, #x1, #o1, #b1)
> CL-USER> (a)
> 0 (0 bits, #x0, #o0, #b0) CL-USER>
> 
> On CLISP or ABCL
> 
> [2]> (a)
> 0
> [3]> (inc-a)
> 1
> [4]> (a)
> 1 [5]>
> 
> Even more worrying to me, I get the same result with 
> (sb-ext:atomic-incf), the (a) function always returns 0.
> 
> Please, can you explain to me like I'm 5 years old why it does not work 
> on SBCL and why it works with other LISP compilers ?
> 
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