On 06/30/2010 05:06:19 AM, Burcin Erocal wrote:
On Fri, 25 Jun 2010 07:53:00 -0700
Mike Witt <[email protected]> wrote:
> On 06/25/2010 06:07:02 AM, kcrisman wrote:
> > Dear Mike,
> >
> > Just to follow up:
> >
> > There is further discussion at
> > http://trac.sagemath.org/sage_trac/ticket/9329
> > if you are interested in saying exactly what sort of data
structure
> > would enable you to perform the simplifications you would like to
> > without having to create a custom Maxima simplification routine.
> >
> > - kcrisman
>
> Well ... I can see how one might work one's way
> through the expression, using the operator() and operands()
> functions. And, I suppose, I can see how one could then build
> up the equivalent expression, having modified one of the
> operands in a certain way. So, I don't suppose that there is
> actually any need for a custom data structure to do this.
As far as I understand from your previous comments, a way to extract
the
exponential functions from the expression is all you need. You don't
really need to walk through the tree. Here is one way to do this:
sage: t = exp(x+y)*(x-y)*(exp(y)+exp(z-y))
sage: t
(e^(-y + z) + e^y)*(x - y)*e^(x + y)
sage: w = SR.wild()
sage: t.find(exp(w))
[e^(-y + z), e^(x + y), e^y]
You can then change the expressions in the given array and substitute
new values for them:
sage: t.subs({res[1]: sin(res[1].operands()[0])})
(e^(-y + z) + e^y)*(x - y)*sin(x + y)
The .operands()[0] syntax is really cumbersome. We need a shortcut for
this. I thought .op(0) worked for pynac expressions before we switched
from the maxima backend.
> Although ... I guess I'm still a bit confused as to why
> this happens, even given the form of the exponential.
>
> sage: f = e^(2*I*pi*n*x - 2*I*pi*n)
> sage: latex(f)
> e^{\left(\left(2 I\right) \, \pi n x + \left(-2 I\right) \, \pi
> n\right)}
>
> Still, I shouldn't really get +(-2i) right?
This is a bug:
http://trac.sagemath.org/sage_trac/ticket/9394
I'll fix this when I have time to work on pynac again.
Cheers,
Burcin
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Thanks. That's a good idea. I'll try that.
-Mike
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