Adam, I am aware that you've been high on ga but must say that I don't think I want to go learn all that. If you can post indicial tensor algebra, general relativity calculations, etc I might be more inclined to take a more detailed look at ga. I do general relativity and wanted to try to see how to help extend the sympy stuff to do indicial tensor analysis ala MathTensor or ITensor in Maxima.
Comer On May 26, 3:56 pm, Alan Bromborsky <[email protected]> wrote: > [email protected] wrote: > > Hi, > > > I am trying to understand some apparently old code written by Ondrej > > trying to implement what I think are indicial tensor expressions. I > > list below the class definitions and then try to give an example. The > > example results in an error. I believe I recall that Ondrej says that > > these definitions don't work, but I am trying to understand them and > > want to try to create some appropriate classes which can contain > > indicial tensors. > > > Here is what he has: > > type(g) > > <class 'certekten.Indexed'> > > from sympy import exp, Symbol, sin, Rational, Derivative, dsolve > > > from sympy.core import Basic, Function > > from sympy.matrices import Matrix > > > class Indexed(Basic): > > def __init__(self, A, idxlist): > > self._args = [A, idxlist] > > > def __str__(self): > > r = str(self[0]) > > for idx in self[1]: > > r+=str(idx) > > return r > > > class Idx(Symbol): > > def __init__(self, name, dim = 4, up = True): > > Symbol.__init__(self, name) > > #self._args.extend([dim,up]) > > self._name = name > > self._dim = dim > > self._up = up > > > def __str__(self): > > if self._up: > > r = "^" > > else: > > r = "_" > > return r+self._name > > > @property > > def up(self): > > return Idx(self._name, self._dim, True) > > > @property > > def dn(self): > > return Idx(self._name, self._dim, False) > > > def values(self): > > return range(self._dim) > > > mu = Symbol("mu") > > nu = Symbol("nu") > > > g =Indexed(Symbol("A"),[mu,nu]) > > > g > > > Among lots of output, the following stands out: > > 'Indexed' object is unsubscriptable > > > What I want is to see g_{\mu,\nu} to give a latex version. > > > So I don't understand what is wrong with the syntax/class def which > > he gave. > > > I would appreciate some help in both learning more about how sympy > > works and on this particular task. > > > Thanks a bunch. > > > Comer > > > And here is a try: > > What are you trying to do with tensors in particular? -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
