[Maxima-bugs] [maxima:bugs] #5091 spectral_rep prints raw Lisp debug output when the spectrum cannot be found

[Barton W. <wil...@us...>]

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

Fixed by Commit [c5762f] . Closing ticket as closed.



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**[bugs:#5091] spectral\_rep prints raw Lisp debug output when the spectrum cannot be found**

**Status:** closed
**Group:** None
**Labels:** share packages printing matrix 
**Created:** Fri Aug 21, 2026 06:50 AM UTC by David Scherfgen
**Last Updated:** Tue Sep 01, 2026 07:39 PM UTC
**Owner:** Barton Willis


```maxima
(%i1) display2d:false$
(%i2) load(linearalgebra)$
(%i3) spectral_rep(matrix([0,0,0,0,1],[1,0,0,0,1],[0,1,0,0,0],[0,0,1,0,0],
                          [0,0,0,1,0]));

(RATVARS = ((MLIST SIMP)) GCD = '$GCD ALGEBRAIC = T)
(RATFAC = NIL) Unable to find the spectrum
 -- an error. To debug this try: debugmode(true);
```

Only the "`Unable to find the spectrum`" error should reach the user. Instead two lines of raw Lisp are printed first, with internal uppercase symbols, a dollar-sign prefix, and an empty Maxima list shown as `((MLIST SIMP))` rather than `[]`. These cannot be switched off. The `GCD` field is also wrong on its own terms: it prints the literal symbol `'$GCD` where its neighbours print values, whereas `gcd` is bound to `spmod` at that point. `matrixexp` on the same matrix produces the identical output, since it goes through `spectral_rep`.

Detected by Claude.


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