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Submitted by : (unknown) at: 2007-11-17T22:03:19-08:00 (10 years ago)
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(new) differentiating sums with respect to a bound is wrong --Bill Page, Wed, 22 Jun 2005 13:55:51 -0500 reply
Update of bug #9216 (project axiom):

Status: None => transferred

Example of code trigerring the bug:

axiom
f:=operator 'f

\label{eq1}f(1)
axiom
D(sum(f(i),i=a..x),x)
>> Error detected within library code: a sum cannot be differentiated with respect to a bound

is nonsense. The problem is in COMBF/dvdsum:

axiom
dvdsum(l, x) ==
  x = retract(y := third l)@SE => 0
  k := retract(d := second l)@K
  differentiate(h := third rest rest l,x) * eval(f := first l, k, h)
  - differentiate(g := third rest l, x) * eval(f, k, g)
  + opdsum [differentiate(f, x), d, y, g, h]
Type: Void

Although this:

d/dx \sum_i^x f(i) = f(x) 

is a nice try, it is wrong. It seems that the order of magnitude is roughly correct, but that's about it.

Unfortunately, I do not know how to return the thing unevaluated, so I cannot fix the bug yet

Continued in Bug #180 --kratt6, Thu, 23 Jun 2005 02:18:19 -0500 reply
Category: => Axiom Compiler Severity: => critical Status: => duplicate




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