Hello,
On Wed, Dec 9, 2009 at 12:44 PM, Nick Alexander <ncalexan...@gmail.com> wrote:
> Implementing a particular symbolic function is not outlandishly
> difficult, thanks to the tireless work of Burcin Erocal and Mike
> Hansen. (Apologies to any contributers I have forgotten.)
>
> You need to subclass sage.symbolic.function.SFunction. I don't see
> many examples, so here is a minimal one:
>
> from sage.symbolic.function import SFunction
> from sage.rings.all import RealField
>
> class bessel_J_class(SFunction):
> def __init__(self, *args, **kwds):
> kwds['nargs'] = 2
> kwds['evalf_func'] = self._evalf_func_
> SFunction.__init__(self, "bessel_J", *args, **kwds)
>
> def _evalf_func_(self, *args, **kwds):
> prec = kwds['prec']
> vals = [ arg.n(prec) for arg in args ]
> v = bessel_J(*vals)
> return RealField(prec)(v)
>
> symbolic_bessel_J = bessel_J_class()
>
> Then the following works for me:
>
> sage: var('x')
> sage: plot(symbolic_bessel_J(0, x), (x, 0, 100))
Things have changed a tiny bit in Sage 4.3 which should make adding
these types of functions a bit easier. See patch # 7490 for lots of
examples.
--Mike
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