'diff(x*y,x) gives the correct result (holds form), while
'diff(x,x) gives 1, calculates the differencial.
Nobody/Anonymous
2009-05-13
I may be stupid or blind, but I do not see the problem here. Would you like to see diff(x*x,x) resulting in x rather than 2x? May be your remark is more subtle than this.
Žiga Lenarčič
2009-05-13
Problem is in quoted diff, which should not evaluate, but it does in 'diff(x,x) case:
(%i2) 'diff(x*y,x);
d
(%o2) -- (x y)
dx
(%i3) 'diff(x,x);
(%o3) 1
(%i4) 'diff(2*x,x);
d
(%o4) -- (2 x)
dx
Dieter Kaiser
2009-11-14
'diff(x,x) gives 1 because of simplification in the simplifying function simpderiv.
We have a similar simplification for integrals:
(%i9) 'integrate(1,x);
(%o9) x
Therefore, we can do something like
(%i10) 'diff('integrate(1,x),x);
(%o10) 1
Furthermore, the following simplification is build in:
(%i15) 'diff(x,x,0);
(%o15) x
This works for an arbitrary expression too:
(%i17) 'diff(sin(x),x,0);
(%o17) sin(x)
It might be arguable why Maxima does not do more simplifications of this type, but the implement simplifications are not wrong. I have no example, where these simplifications cause problems.
So, I would suggest not to change the behavior of Maxima to simplify the examples in this bug report.
Setting the status to pending and resolution "works for me".
Dieter Kaiser
Dieter Kaiser
2009-11-14
SourceForge Robot
2009-11-29
This Tracker item was closed automatically by the system. It was
previously set to a Pending status, and the original submitter
did not respond within 14 days (the time period specified by
the administrator of this Tracker).
SourceForge Robot
2009-11-29