On Sat, 21 Mar 2009 03:02:57 -0700
Robert Bradshaw <[email protected]> wrote:
>
> On Mar 21, 2009, at 2:01 AM, Craig Citro wrote:
>
> >> I think that better way is to use maxima commands op, args, length,
> >> atomp
> >>
> >
> > I think that for objects which come from Maxima, this is the right
> > thing to do. However, not all symbolic objects in Sage are wrappers
> > for Maxima objects -- in the case of expressions using pynac, the
> > code above actually moves them over to Maxima (via strings and
> > pexpect) and then ask for their length there (which probably
> > ultimately uses the commands you mention). This is less than
> > desirable, hence my claim that it was a terrible way to calculate
> > the length. :)
> >
> > I think a first step might be to introduce a __len__ method for
> > symbolic objects, but then, I'm not always sure what it should
> > return.
>
> I would argue that this is a good reason not to implement it :).
> Something like nops would be trivial to implement though, and
> probably a good idea.
>
It's in pynac already:
sage: var('x,y',ns=1)
(x, y)
sage: f = expand((1+x+1/y)^10)
sage: f.nargs()
66
I could hook this up to __len__ as well, since __getitem__ lets you
access parts of the expression. E.g.,
sage: f[0]
x^10
sage: f[1]
10*x^9
Cheers,
Burcin
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