2. What functionality would you like to see added to GSL?
I would like to see better support for complex functions. In particular,
I need bessel functions which can take complex arguments and return
complex results.
Also, support for the C99 complex type would be highly desirable. The
gsl_complex type is really quite unwieldy when expressing large
arithmetic expressions. FFTW style integration with the C99 complex type
would be worth emulating.
http://www.fftw.org/doc/Complex-numbers.html
3. Are you willing to develop and contribute the features you want?
Yes, definitely. I have code for calculating a few bessel functions (Jn,
Y0, H01) with complex arguments. I also have a routine for romberg
numerical integration which operates on functions with complex arguments
and complex results. I would happily contribute these routines to GSL. I
haven't done yet because I wasn't quite sure how complex functions
fitted neatly into the rest of GSL. So, better integration with the C99
complex type is really important for me.