On Wed, Feb 15, 2012 at 11:28 PM, Robert Dodier <robert.dodier at gmail.com>wrote:
> On 2/15/12, Stavros Macrakis <macrakis at alum.mit.edu> wrote:
>
> > diff(x,tan(x)) => 0
> > diff(x,f(x)) => 0
> >
> > but not
> >
> > diff(x,1+x) => error
> >
> > In principle, all of these could of course be meaningful, but Maxima
> > doesn't know that.
> >
> > Which seems more useful for users in such cases?:
> >
> > * Giving an error?
> > * Leaving as noun forms? (which Maxima can't do anything useful with)
>
> Well, in general it seems useful, and consistent with Maxima's
> behavior in other cases, to return a noun form. Then sufficiently
> clever people (whether it's the developers or anybody else) can
> impose an interpretation of such expressions via the simplification
> system.
>
Returning a noun form does seem to be Maxima's standard behavior, but I
often find it rather annoying. Say I do an integral and I get a noun form
back. Not because maxima can't really do the integral but because some
function deep in the bowels of the integration routines failed. Rather
than giving some indication of that, maxima silently returns a noun form.
Noun forms are nice for users, but sometimes painful for developers.
I don't know what the right balance should be.
Ray