FWIW, here is a patch for more accurate bessel functions. It should be a relatively safe patch because it only modifies j[0]-bessel, j[1]-bessel, i[0]-bessel, and i[1]-bessel. I've tested some random values and they appear to match the tables in A&S to the last digit or so. As mentioned earlier, this is a translation of some routines from TOMS 715 via f2cl and therefore includes some of the macros used by f2cl. It would be possible to remove the use of the f2cl macros, but I'd rather not. Ray
Attached file: bessel.patch