Mark Dickinson added the comment: Unfortunately, implementing asinh, acosh, atanh correctly is not as simple as just using the formulas (this is one of the reasons that it's useful to be able to get at the library definitions). For example, the formula
asinh(x) = log(x + sqrt(1.+(x*x))) has significant error (i.e. much more than just a few ulps) when x is small (so that the argument of the log is close to 1), and when x is large and negative (so that the addition involves adding two numbers of almost equal magnitude but opposite sign). It also overflows unnecessarily at around 1e154 (on an IEEE754 system), as a result of the intermediate calculation x*x overflowing, and it fails to give the correct signs on zero arguments. (asinh(0.) = 0., asinh(-0.) = -0.) So either some serious work is required here, or code should be borrowed in an appropriately legal fashion from some other library, or those few people who don't have asinh, acosh, etc. already in libm will have to live without. Mark __________________________________ Tracker <[EMAIL PROTECTED]> <http://bugs.python.org/issue1640> __________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
