Hi, I think that this is related to
http://trac.sagemath.org/sage_trac/ticket/7661
and probably gets positive review within few hours :) .
R.
On 10 dub, 18:37, Harald Schilly <harald.schi...@gmail.com> wrote:
> Hi, I got this from the "report a problem" public bugtracker. I don't
> know if this is already known but it's a nice example that there is
> something odd in the symbolics code. I can confirm it in 4.3.5.
>
> """The script below calculates the eigenvalues for a matrix, M. I want
> to use 'delta' as a symbolic variable, such that it renders as the
> greek letter \delta when typeset in the notebook. However, when I do
> this it would seem that sage thinks it's a Dirac delta function and
> throws an error. Other choices of variable names, such as theta, do
> not do this."""
>
> Examples:
>
> The following script throws a TypeError:
> f,b,m,ku,du,kt,l,d = var('f beta_s mu k_u d_u k_t lambda delta')
> ### Replacing 'delta' with, say, theta, does not give the problem
> w = (1-f) * b
> x = f * b
> y = m + ku + du
> z = m + kt
> M = matrix([[w/y,d*w/z],[x/y,d*x/z]])
> I = matrix(2,2,1)
> s = M - l*I
> p = det(s)
> p.solve(l) ### M.eigenvalues() will do the same
>
> gives:
> TypeError: unsupported operand parent(s) for '*': 'Symbolic Ring' and
> '<class 'sage.functions.generalized.FunctionDiracDelta'>'
>
> Here a minimal example:
>
> sage: x,d = var('x delta')
> sage: solve([x+d==0],x)
>
> gives:
> TypeError: bad operand type for unary -: 'FunctionDiracDelta'
>
> h
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