Re: SBCL tells me it is deleting unreachable code that is almost surely reachable

On 4/15/26 8:25 AM, Barton Willis via Maxima-discuss wrote:

> Here is a revision of a function in hayat. The revision eliminates or 
> helps to eliminate two testsuite failures.
>
> The SBCL (2.4.7)  compiler tells me that
>
> ; file: C:/Users/barton/maxima-code-pure/maxima-code/src/./hayat.lisp
> ; in: DEFUN COEF-SIGN
> ;     (EQ MAXIMA::SGN 'MAXIMA::$POS)
> ;
> ; note: deleting unreachable code
>
> I think that is rubbish—likely, I'll commit the (commented out) memq 
> version.

Check to see what |$csign| returns? Or rather what csign-impl returns. 
For me, I see the return type is * (anything).

|memq| should do exactly the same as testing |(or (eq sgn '$neg) (eq sgn 
'$zero) (eq sgn '$pos))|. Well, it would if it were declared inline, but 
it’s not.

Seems to me that it would be easy to test if that code were actually 
deleted by calling |coef-sign| with an arg that is known to be |$pos|.

>
> (defun coef-sign (coef)
>   (let ((sgn ($csign coef)))
>     (cond ((or (eq sgn '$complex) (eq sgn '$imaginary)) '$im)
>           ;((memq sgn '($neg '$zero '$pos)) sgn)
>           ((or (eq sgn '$neg) (eq sgn '$zero) (eq sgn '$pos)) sgn)
>           (t
>              (let ((asgn ($asksign coef)))
>                 ;; When sgn is zero and limit is active, record this 
> fact as a noun equality
>                 ;; in *limit-assumptions*.
>              (when (and *limit-assumptions* (eq asgn '$zero))
>                (push (ftake '$equal coef 0) *limit-assumptions*))
>             asgn)))))
>
>
>
> _______________________________________________
> Maxima-discuss mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/maxima-discuss
​

_______________________________________________
Maxima-discuss mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/maxima-discuss