[Maxima] Contrib ODE vs integrate
Billinghurst, David CALCRTS
david.billinghurst at comalco.riotinto.com.au
Sat May 13 19:57:30 CDT 2006
> From: Raymond Toy
> A while back, I changed integrate to fix the long-standing
> bug, integrate(sqrt(x+1/x-2),x,0,1). The cause of this bug was in
> intform where it set radexpand:all. This caused maxima to convert
> sqrt((x-1)^2) to x-1, when 1-x was really wanted.
> However, I see this this change breaks a lot of tests in the
> contrib ODE
> package; that was not intentional. At this point, I see a
> few solutions.
> o Revert the change, reinstating the old bug.
> o Leave the change in and accept the failures in ODE
> (and/or adjust ODE tests appropriately)
OK with me. I've started on this by disabling tests that
fail so we have clean results. I am sure that analysis of
the failures will find all sorts of bugs - some of them mine.
> o Add a new variable to allow the user to control what
> value of radexpand will used in intform.
> o Change intform so it doesn't touch radexpand, so it uses
> whatever the current value is.
The second option seems easier to implement. I guess we set a safe
default and allow users to relax this if they have additional knowledge.
> I do not know if the last option will fix the ODE test
> failures or not.
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