I am looking for a complex-number approximation formula for the Jacobi Theta Functions that only uses simple functions. By simple, I mean supported natively by most programming languages and does not involve too many special functions as prerequisites like what C++ has, thus I may implement the formula using different languages.
I have searched on the Digital Library of Mathematical Functions and the Wolfram Functions Site, but still do not find anything other than infinite series or products.
Thanks for reading.
