Hi!
On 2013-02-07, Olajumoke Yetunde Fashomi <yetu...@aims.ac.za> wrote:
> Thanks for your concern, F is a function of y which are the non-linear
> terms in the second order initial value problem. The purpose of the y[n] is
> to generate a recursive relation for the polynomials
I think John was not asking how F is defined mathematically, but how F
was defined in your Sage session. Namely, the code snippet you provided
does not contain a definition of F and would thus simple yield a
NameError.
> On 7 February 2013 21:16, john_perry_usm <john.pe...@usm.edu> wrote:
>> Out of curiosity, how is F defined?
>>
>> I don't know if this is the cause, but when I try something similar, I
> get a
>> problem with y[n]: 'sage.symbolic.expression.Expression' does not support
>> indexing. Since it's a different error, you're probably encountering
>> something else.
I suppose John tested something like the following.
sage: var('y')
y
sage: y[1]
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-3-c3672a1efa28> in <module>()
----> 1 y[Integer(1)]
TypeError: 'sage.symbolic.expression.Expression' object does not
support indexing
Hence, as you see, one gets an error message that differs from what you
reported.
That said, it is rather likely that y[n] is the problematic spot in your code,
because symbolic expressions simply don't support that syntax.
Best regards,
Simon
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