These are chat archives for symengine/symengine

14th
Apr 2017
Isuru Fernando
@isuruf
Apr 14 2017 02:23
@ChrisRackauckas, it's not in SymEngine.jl. diff(f(x), x) gives a derivative when f is unknown
Christopher Rackauckas
@ChrisRackauckas
Apr 14 2017 02:33
Where it's that defined? I assume the function needs to be imported into the scope from somewhere?
Isuru Fernando
@isuruf
Apr 14 2017 02:34
you mean diff?
Christopher Rackauckas
@ChrisRackauckas
Apr 14 2017 02:34
Yeah
Isuru Fernando
@isuruf
Apr 14 2017 03:20
@ChrisRackauckas, how do you want to handle unknown functions?
Christopher Rackauckas
@ChrisRackauckas
Apr 14 2017 03:50
I was not sure how you coded them in before.
Because I know erf works
so I wanted to see if I could "plug into" whatever system there was
and just define a derivative for a function.
if there isn't, that's fine.
Isuru Fernando
@isuruf
Apr 14 2017 03:51
erf is a known function in symengine
Christopher Rackauckas
@ChrisRackauckas
Apr 14 2017 03:51
I see
Isuru Fernando
@isuruf
Apr 14 2017 03:52
I do have some work in progress where you can do for example register(:erf, :(2*exp(-x**2)/sqrt(pi)))
is this what you were looking for?
For multi-arg, register(:beta, :((polygamma(0, x) - polygamma(0, x + y))*beta(x, y)), :((polygamma(0, y) - polygamma(0, x + y))*beta(x, y)))
Christopher Rackauckas
@ChrisRackauckas
Apr 14 2017 03:57
yeah, that's the kind of stuff I was thinking of