[Maxima-bugs] [maxima:bugs] #4752 csign doesn't handle subscripted functions like li correctly

[David S. <tom...@us...>]

- **status**: open --> closed
- **Comment**:

Fixed by commit	[4c2ce8].



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**[bugs:#4752] csign doesn't handle subscripted functions like li correctly**

**Status:** closed
**Group:** None
**Labels:** csign sign complex li 
**Created:** Wed Jun 03, 2026 10:29 AM UTC by David Scherfgen
**Last Updated:** Wed Jun 03, 2026 10:29 AM UTC
**Owner:** nobody


OK for normal functions:

~~~
(%i1) declare(f, complex)$

(%i2) csign(f(x));
(%o2) complex
~~~

Wrong for subscripted functions like `li`:

~~~
(%i1) featurep(li, complex);
(%o1) true

(%i2) csign(li[n](x));
(%o2) pnz
~~~

Caused by this code in `sign-any` (compar.lisp) not handling subscripted functions correctly:

~~~
        ((and *complexsign*
              (not (atom x))
              (decl-complexp (caar x)))
         ;; A function f(x), where f is declared to be imaginary or complex.
         (if ($featurep (caar x) '$imaginary)
             (setq sign '$imaginary)
             (setq sign '$complex)))
~~~


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