# Axiom Computer Algebra System - Bugs: bug #9218, problems with output of D

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# bug #9218: problems with output of D

 Submitted by: Martin Rubey Submitted on: Fri 04 Jun 2004 08:26:31 AM UTC Category: None Severity: 3 - Normal Item Group: code bug Status: None Privacy: Public Assigned to: None Originator Name: kratt6 Open/Closed: Open Release: tla from may 2004 Reproducibility: None Fixed Release: Error message: Example of code trigerring the bug: eval(D(f(x),x),f,y+->sum(g(i,y),i=a..y)) Internal cause: I think, the real internal cause is that axiom assumes that everything can be nicely differentiated, thus not providing a possibility of returning an unevaluated differential operator... Also consider: (13) -> D(f(x,x),x)    (13)  f  (x,x) + f  (x,x)           ,2         ,1                                                      Type: Expression Integer (which is correct)

## Discussion

Fri 04 Jun 2004 08:28:53 AM UTC, comment #1:

I forgot to add the following:

(17) -> eval(z,x,2)

(17)  %defsum  (g(%C),%C,i,a,2)
,5
Type: Expression Integer

is questionable (but may be interpreted correctly)

Martin

Martin Rubey <kratt6>
Fri 04 Jun 2004 08:26:31 AM UTC, original submission:

eval(D(f(x),x),f,y+->sum(g(i),i=a..y))

(9)  %defsum  (g(%A),%A,i,a,x)
,5

although this is correct, it looks rather strange...

Worse:

(12) -> eval(D(f(x),x),f,y+->sum(g(i,y),i=a..y))

(12)  %defsum  (g(%A,%%01),%A,i,a,x)
,5
Type: Expression Integer

Martin Rubey <kratt6>

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## Dependencies

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## History

Follows 1 latest change.

Date Changed by Updated Field Previous Value => Replaced by
2008-11-25 axiom Internal causeI think, the real internal cause is that axiom assumes that everything can be nicely differentiated, thus not providing a possibility of returning an unevaluated differential operator... Also consider: (13) -> D(f(x,x),x) (13) f (x,x) + f (x,x) ,2 ,1 Type: Expression Integer (which is correct) I think, the *real* internal cause is that axiom assumes that everything can be nicely differentiated, thus not providing a possibility of returning an unevaluated differential operator... Also consider: (13) -> D(f(x,x),x) (13) f (x,x) + f (x,x) ,2 ,1 Type: Expression Integer (which is correct)