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#19 D(0^z, z) fails

Edit detail for #19 D(0^z, z) fails revision 2 of 2

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Editor: kratt6 Time: 2007/12/28 12:57:43 GMT-8
Note:

added:

From kratt6 Fri Dec 28 12:57:43 -0800 2007
From: kratt6
Date: Fri, 28 Dec 2007 12:57:43 -0800
Subject: 
Message-ID: <20071228125743-0800@axiom-wiki.newsynthesis.org>

Category: Axiom Mathematics => Axiom Library

axiom

D(0^z, z)

$\label{eq1}0$

(1)

Type: Expression(Integer)

Produced:

   >> Error detected within library code:
   Invalid argument

Of course, 0 is expected.

patch --kratt6, Thu, 20 Jan 2005 07:29:04 -0600 reply

The offending code is in combfunc.spad, here is a patch. Note however, that strictly speaking 0^z is not differentiable at 0:

  @@ -405,7 +417,10 @@
         iipow l == ipow l

       if F has ElementaryFunctionCategory then
  -      dvpow2 l == log(first l) * first(l) ** second(l)
  +      dvpow2 l == if zero?(first l) then
  +                    0
  +                  else
  +                    log(first l) * first(l) ** second(l)

       evaluate(opfact, iifact)$BasicOperatorFunctions1(F)
       evaluate(oppow, iipow)