#4735: Make e^X try calling X.exp() before trying to coerce X to the symbolic
ring
-------------------------+--------------------------------------------------
Reporter: jason | Owner: burcin
Type: enhancement | Status: new
Priority: major | Milestone: sage-3.2.2
Component: calculus | Resolution:
Keywords: |
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Old description:
> From sage-devel:
> {{{
> > I'd like to add an exponential function to RDF/CDF matrices (and
> > > enhance
> > > the existing exp function for SR matrices) so that:
> > >
> > > sage: A = matrix(SR, [[1,2],[3,4]])
> > > sage: e^A
> > >
> > > gives the same as
> > >
> > > sage: A.exp()
> > >
> > > (I'd also like this to work for other matrices, like over RDF or CDF,
> > > where the returned matrix would be another RDF/CDF matrix---scipy has
> > > functions that do this).
> > >
> > > However, currently for constants (in sage/functions/constants.py),
> the
> > > __pow__ function automatically converts the exponent to an SR object,
> > > which fails for a matrix.
> > >
> > > I have not worked with the constants code before. Would there be a
> > > problem with, for the E constant, overriding __pow__ so that if the
> > > object had an "_exp" method, that was called instead of the default
> > > conversion to SR objects?
>
> +1, this was my first though when I started reading your email. I
> don't think it makes sense for other constants, but for E it
> certainly does. Also, I'd just call exp (not _exp), making sure that
> it doesn't introduce a recursive call...
>
> > > Would that be the proper way to get the above functionality? The
> goal
> > > is also to get exp(A) to work as well; would I get that for free?
>
> Yes. When you do exp(A) it attempts to return A.exp() before doing
> anything symbolic.
> }}}
New description:
From sage-devel at http://groups.google.com/group/sage-
devel/t/ff6cdb898792d5b3 :
{{{
> I'd like to add an exponential function to RDF/CDF matrices (and
> > enhance
> > the existing exp function for SR matrices) so that:
> >
> > sage: A = matrix(SR, [[1,2],[3,4]])
> > sage: e^A
> >
> > gives the same as
> >
> > sage: A.exp()
> >
> > (I'd also like this to work for other matrices, like over RDF or CDF,
> > where the returned matrix would be another RDF/CDF matrix---scipy has
> > functions that do this).
> >
> > However, currently for constants (in sage/functions/constants.py), the
> > __pow__ function automatically converts the exponent to an SR object,
> > which fails for a matrix.
> >
> > I have not worked with the constants code before. Would there be a
> > problem with, for the E constant, overriding __pow__ so that if the
> > object had an "_exp" method, that was called instead of the default
> > conversion to SR objects?
+1, this was my first though when I started reading your email. I
don't think it makes sense for other constants, but for E it
certainly does. Also, I'd just call exp (not _exp), making sure that
it doesn't introduce a recursive call...
> > Would that be the proper way to get the above functionality? The goal
> > is also to get exp(A) to work as well; would I get that for free?
Yes. When you do exp(A) it attempts to return A.exp() before doing
anything symbolic.
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4735#comment:2>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
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