Anyone interested in the gory details of how elementary functions are calculated in floating-point arithmetic might take a look at fdlibm, in particular
http://netlib.org/fdlibm/e_exp.c which is the source for exp. This demonstrates two common techniques: argument reduction, and using interpolation based on polynomials with precomputed coefficients. The polynomials tend not to be Taylor polynomials (which minimize error near a point) but Chebyshev polynomials (which minimize mean square error over an interval). The code here claims to have error less than 1 ulp (unit in the last place). Best wishes, John ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
