Original Savannah bug 9217

Submitted by: Martin Rubey

Submitted on: Fri 06/04/04 at 08:18

Summary:

Although axiom can evaluate this sum, it does not.

Example of code trigerring the bug:

axiom

f := operator 'f

axiom

sum(f(i),i=a..b)

**Type: **Expression(Integer)

axiom

eval(%,f,x+->x)

**Type: **Expression(Integer)

## Internal Cause

first the sum is evaluated. Since the argument `f(x)`

is not a polynomial
or rational function, using first iidsum, than idsum of COMBF. Afterwards
the substitution is performed. Now the sum has the internal format
'%defsum [%A, %A, i, a, b]?', which is again evaluated with iidsum and idsum of
COMBF. The function `sum$InnerPolySum`

is never called, of course. A general
solution is to call sum from within idsum, but in this case, care has to be
taken that summation algorithms that can fail (such as Gosper's) do not
produce an infinite loop. (In fact I think this is OK, I only did not have
the time to check)

Category: => Axiom Library
Severity: => serious
Status: => open

property change--kratt6, Tue, 04 Oct 2005 05:47:07 -0500 reply