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Re: [Axiom-developer] severe (!) bug in normalize

From: Francois Maltey
Subject: Re: [Axiom-developer] severe (!) bug in normalize
Date: 05 Dec 2006 21:18:20 +0100
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.4

Dear Martin, and others...

> I just discovered a severe bug in normalize$EFSTRUC. It is probably the worst
> thing I found so far.
> with
>  T :=t^(n^2)*(sqrt(1+t))^n
>  normalize(T/eval(T, n=n-1))
> gives sqrt(t+1). sum$SUMFS uses this method to check whether a function is
> rational for Gosper, and thus returns completely false results, which are,
> however, difficult to detect.
> Waldek, am I right that you know normalize a little bit? 
> If you do, PLEASE look into this, it is a real show stopper for me.

I'm testing some patchs in expr.spad.
On my today-version I get : 

(64) -> T := t^(n^2)*sqrt(1+t)^n
          n   +-----+n
   (64)  t   \|t + 1
                                                     Type: Expression Integer
(65) -> T/subst (T, n=n-1)
          2n - 1 +-----+
   (65)  t      \|t + 1
                                                     Type: Expression Integer
(68) -> normalize (T/eval (T, n=n-1))
          +-----+  (2n - 1)log(t)
   (68)  \|t + 1 %e
                                                     Type: Expression Integer

Do you want this expr.spad ?

Attachment: expr.spad
Description: a new expr.spad file

There are some buggy print inside.

I hope it shall work for you.

I also must change very few lines in others files.

If you want to compile and test it.


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