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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