Hi Alex,

On Mon, 16 Mar 2009 19:26:26 -0700 (PDT)
Alex Raichev <tortoise.s...@gmail.com> wrote:

> 
> ----------------------------------------------------------------------
> | Sage Version 3.4, Release Date: 2009-03-11                         |
> | Type notebook() for the GUI, and license() for information.        |
> ----------------------------------------------------------------------
> sage: var('x,y', ns=1)
> (x, y)
> sage: f= x+y
> sage: type(f)
> <type 'sage.symbolic.expression.Expression'>
> sage: jacobian(f,[x,y])
> ---------------------------------------------------------------------------
> TypeError                                 Traceback (most recent call
> last)
> 
> /Users/arai021/<ipython console> in <module>()
> 
> /Applications/sage/local/lib/python2.5/site-packages/sage/calculus/
> functions.pyc in jacobian(functions, variables)
>     136
>     137     if not isinstance(variables, (tuple, list)) and not
> is_Vector(variables):
>     138         variables = [variables]
>     139
> --> 140     return matrix([[diff(f, v) for v in variables] for f in
> functions])
> 
> /Applications/sage/local/lib/python2.5/site-packages/sage/calculus/
> functional.pyc in derivative(f, *args, **kwds)
>     145         pass
>     146     if not isinstance(f, SymbolicExpression):
> --> 147         f = SR(f)
>     148     return f.derivative(*args, **kwds)
>     149
<snip>
> TypeError: cannot coerce type '<type
> 'sage.symbolic.expression.Expression'>' into a SymbolicExpression.

You get this error because pynac expressions don't define
a .derivative() function. I also noticed that the interface for .diff()
doesn't match the rest of Sage.

I'll fix this and post a patch when I find the time. That will be this
evening, or sometime tomorrow.

Thanks.

Burcin

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