On 10/17/07, William Stein <[EMAIL PROTECTED]> wrote:
>
> On 10/17/07, David Joyner <[EMAIL PROTECTED]> wrote:
> > The commands
> >
> > [EMAIL PROTECTED]:~/sagefiles/sage-2.8.2> ./sage
> > ----------------------------------------------------------------------
> > | SAGE Version 2.8.5, Release Date: 2007-09-21 |
> > | Type notebook() for the GUI, and license() for information. |
> > ----------------------------------------------------------------------
> > sage: t = var('t')
> > sage: x = function('x', t)
> > sage: (m,b,k,w,g,F0) = var("m,b,k,w,g,F0")
> > sage: de = lambda y: diff(y,t,t) + w^2*y - F0*cos(g*t)
> > sage: F0 = 1; g = 1; w = 2
> > sage: desolve_laplace(de(x(t)),["t","x"],[0,0,0])
> > 'cos(t)/3-cos(2*t)/3'
> >
> > work fine on the command line but online (using the
> > sage.math notebook) they give an error
> >
> > Exception (click to the left for traceback):
> > ...
> > TypeError: unsupported operand parent(s) for '+': '<type 'str'>' and
> > 'Symbolic Ring'
> >
> > This is an issue since this specific problem is a
> > possible assignment for my DEs classes this semester.
> > Some students can't install the SAGE software due to
> > inexperience with computers, so I wanted to give them
> > the option of using sage.math instead.
>
> (1), this works fine on the public notebooks. I just tried
> and it worked without any trouble. See
> https://sage.math.washington.edu:8103/home/pub/1493/
There is something about worksheets which I don't understand.
When I copy and paste the code in your worksheet linked above
into my old worksheet which had the error message, the problem
re-occurred. When I copy and paste the code in your worksheet
into a new worksheet, it disappeared.
It seems to me that this should not happen, but maybe that it
indended behavior.
>
> (2) Having a class actually depend in a fundamental way
> on the public notebook servers that I make available is
> a very bad idea. I must emphasize that I reserve the right
> to -- possibly permanently -- take them down at any time.
Well understood, and I have explained that to some of them.
I've only heard of 4 or 5 students attempting the online version
but based on limited experience most prefer to have the
program loaded on their machine (which surprised me).
> One issue is that, as has been discussed here before, there
> are numerous security issues, and at some point people will
> use the public notebook in a way that will require their complete
> removal permanently. For example, if spammers / p0rnographers
> found out about them, they could just post bad content to them
> and use them as an advertising portal or something -- there is
> no way to prevent this short of not giving out accounts and/or
> creating a spam filtering system (which would take quite a while).
> Another issue is simple usage. The sage notebooks currently
> run on a machine that's mainly devoted to research (sage.math)
> and sage development. Unfortunately when the public notebooks
> become too popular -- which will happen at some point -- they will
> start to use all the resources of that machine, and I will have to
> turn the notebooks off, because that machine is needed for other
> computations. (This might be an issue, if I'm able to get new
> hardware before this happens...)
>
> Anyway, there are numerous reasons why having classes depend on the
> public sage notebook server at UW isn't recommended at present.
> The public sage notebooks could be a service like Google mail or maps
> or something, if there were a lot of money available to support a person
> or people to maintain it along with money for sufficient hardware, etc.
>
> Is it possible you could give students a shell account on a machine
> at USNA, at least?
Okay, I'll work a little harder on that and also encourage the students to
use the downloaded version.
>
>
> William
>
> >
>
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