Subject: The factor function is a little bit silly.
From: J.C. Pizarro
Date: Mon, 7 Apr 2008 13:45:25 +0200
I've 2 issues here:
FIRST: Halting problem in TM
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The below symbolic example doesn't terminate after many minutes in
maxima-5.14.0 although the human solution is f(x)-g(x)-h(x):
factor(expand((f(x)-g(x)-h(x))^500));
To fix this problem in the future: better artificial sustitution in the
solving of factor or intelligent lazy computation as
factor(expand(Alpha)) => Alpha.
SECOND: Non-deterministic Memoization
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With
factor(expand((sqrt(x+a)+b)^10));
i got once the imprecise solution
10 b x^4 sqrt(x+a) + 120 b^3 x^3 sqrt(x+a) + ... + 45 a^4 b^2 + a^5
but i got many times (sqrt(x+a)+b)^10 .
I think that the maxima system uses memoization that remember some internal
answers of previous computations but it's non-deterministic.