On Sunday, November 8, 2015 at 5:45:44 PM UTC+2, Imran Ali wrote:
>
> I was a bit quick there. srepr(u) gives the following output :
>
> BaseScalarField(CoordSystem(Symbol('egg_carton'), Patch(Symbol('P'),
> Manifold(Symbol('M'), Integer(2))), Tuple(Symbol('u'), Symbol('v'))),
> Integer(0))
>
> On Sunday, November 8, 2015 at 4:40:45 PM UTC+1, Imran Ali wrote:
>>
>> Hi Kalevi!
>>
>> I got the following output from srepr :
>>
>> Symbol('u')
>> Differential(BaseScalarField(CoordSystem(Symbol('egg_carton'),
>> Patch(Symbol('P'), Manifold(Symbol('M'), Integer(2))), Tuple(Symbol('u'),
>> Symbol('v'))), Integer(0)))
>>
>> I see now what the error is! My code used u as a sympy expression,
>> instead of it being one of the coord_functions().
>>
>> Thanks!
>>
>> On Friday, November 6, 2015 at 5:51:40 PM UTC+1, Kalevi Suominen wrote:
>>>
>>>
>>>
>>> On Thursday, November 5, 2015 at 3:56:09 PM UTC+2, Imran Ali wrote:
>>>>
>>>> If I simply hard code each metric, every thing works properly. For
>>>> example, take egg carton surface,
>>>>
>>>> from sympy.diffgeom import Manifold, Patch, CoordSystem,
>>>> TensorProduct
>>>> from sympy import sin,cos
>>>> dim = 2
>>>> m = Manifold("M",dim)
>>>> patch = Patch("P",m)
>>>> system = CoordSystem('egg_carton', patch, ["u", "v"])
>>>> u,v = system.coord_functions()
>>>> du,dv = system.base_oneforms()
>>>> metric = (sin(v)**2*sin(u)**2 + 1)*TensorProduct(dv, dv) +\
>>>> (cos(v)**2*cos(u)**2 + 1)*TensorProduct(du, du) +\
>>>> (-cos(2*v - 2*u)/8 + cos(2*v + 2*u)/8)*TensorProduct(du,
>>>> dv) +\
>>>> (-cos(2*v - 2*u)/8 + cos(2*v + 2*u)/8)*TensorProduct(dv,
>>>> du)
>>>> I can use any of the metric_to_* functions without getting the
>>>> ValueError.
>>>>
>>>> By the way, that metric expression, is from my code. My code produces
>>>> the correct metric two form expression. But when I use it as argument for
>>>> any of the metric_to_* functions, I get the ValueError. What gives ?
>>>>
>>>> I posted the question on SO :
>>>>
>>>>
>>>> http://stackoverflow.com/questions/33545982/valueerror-using-sympy-diffgeom-when-using-metric-to-functions
>>>>
>>>>
>>>
>>> It is not clear how u, v, du, dv are constructed in your SO question. If
>>> you could post srepr(u) and srepr(du), it might be possible to say more.
>>>
>>
It looks like u was defined differently in different contexts.
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