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.
>
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