Bill Allombert on Tue, 23 Sep 2014 16:04:03 +0200 |
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Re: [PATCH] enable basic arithmetic with infinity |
On Tue, Sep 23, 2014 at 03:37:05PM +0200, Jeroen Demeyer wrote: > Dear pari-dev, > > The attached patch enables basic arithmetic with t_INFINITY. It adds > support for addition, subtraction, multiplication and division of > infinity by something (division by infinity is still an error). In > all cases, the other operand must be a t_INT, t_REAL or t_FRAC. Purposefully, we restricted the semantic attached to oo. Most of the time such operations are the symptom of a bug. > This patch (at least for multiplication) is needed to support Denis > Simon's 2-descent script which does things like > > if (lambda > 2*valuation(x,p),...) > > where x can be 0. This gave no problems with PARI-2.7 and earlier > because valuation(0,p) returned a very large number. In this instance the assumption was that lambda is always smaller than twice the large number returned by valuation(). This is a known issue in Denis scripts that I have fixed locally. Please send me the versions you use and I will send you the fixed versions. (the change is very small: basically if (lambda > 2*valuation(x,p) become if (x!=0 && lambda > 2*valuation(x,p),... at a couple of place). Sorry or the trouble. Cheers, Bill.