[Maxima-bugs] [maxima:bugs] #5695 fullratsimp(rat(sqrt(c-1)/(c-f(a))^(3/2)-1/(sqrt(c-1)*sqrt(c-f(a))))) loops forever

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

A better version:

~~~
(defmvar *max-fullratsimp-iterations* 32
  "Maximum number of iterations allowed for fullratsimp before falling back.")

(defmfun ($fullratsimp :properties ((evfun t))) (exp &rest argl)
  "Repeatedly applies `ratsimp` to `exp` until either (a) a fixpoint is reached,
   (b) a cycle is detected, or (c) the number of iterations exceeds 
   *max-fullratsimp-iterations*."
  (labels ((local-ratsimp (e)
             (simplify (apply #'$ratsimp e argl))))
    (let* ((k *max-fullratsimp-iterations*)
           (seen (list exp))
           (current exp)
           (next (local-ratsimp exp))
           (best exp)
           (min-size (conssize exp)))
      (loop
        ;; Track the minimum size on the fly
        (let ((sz (conssize next)))
          (when (< sz min-size)
            (setf min-size sz
                  best next)))

        ;; (a) Fixpoint reached
        (when (alike1 current next)
          (return next)) ; or current, they are alike

        ;; (b) Cycle detected or (c) Max iterations exceeded
        (when (or (member next seen :test #'alike1) (< k 0))
          (return best))

        (push next seen)
        (decf k)
        (setf current next
              next (local-ratsimp next))))))
~~~


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**[bugs:#5695] fullratsimp\(rat\(sqrt\(c-1\)/\(c-f\(a\)\)^\(3/2\)-1/\(sqrt\(c-1\)\*sqrt\(c-f\(a\)\)\)\)\) loops forever**

**Status:** closed
**Group:** None
**Labels:** fullratsimp 
**Created:** Thu Oct 22, 2026 03:06 AM UTC by David Scherfgen
**Last Updated:** Thu Oct 22, 2026 08:11 PM UTC
**Owner:** nobody


Discovered by Claude:

~~~
fullratsimp(rat(sqrt(c-1)/(c-f(a))^(3/2)-1/(sqrt(c-1)*sqrt(c-f(a)))));
~~~

This loops forever, cycling over two representations.


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