On Wed, Jun 10, 2009 at 3:16 PM, Jason Grout<jason-s...@creativetrax.com> wrote:
> That's how I'd write it in class if I was illustrating the chain rule.
>
> I agree with Robert---functions have ordered, named parameters (thanks
> to your patch that deprecated not specifying the order of variables!),
> so we should be able to convert back and forth between D[i](f) and
> \frac{df}{d<parameter>} or \frac{\partial f}{\partial<parameter>}
> unambiguously.
No, it's not that easy. These really are two different things.
Converting from the D[] notation to the diff() notation requires the
introduction of a dummy variable and an evaluation. Functions don't
have ordered, named parameters associated to them. Consider the
following:
sage: x, y = var('x,y')
sage: f = function('f')
sage: f(x*y).diff(x)
y*D[0](f)(x*y)
Note that "f = function('f', x)" is the same as "f = function('f')(x)".
The correct solution is to make GiNaC know about both types of expressions.
--Mike
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to sage-devel@googlegroups.com
To unsubscribe from this group, send email to
sage-devel-unsubscr...@googlegroups.com
For more options, visit this group at http://groups.google.com/group/sage-devel
URLs: http://www.sagemath.org
-~----------~----~----~----~------~----~------~--~---
