From edf2210221f2803dfea62493ebff5eafd5cbc851 Mon Sep 17 00:00:00 2001 From: Tim Peters Date: Wed, 21 Feb 2001 03:22:39 +0000 Subject: [PATCH] Bug #133297: cmath.asin is the same as cmath.asinh. The bug report title isn't correct, but was on the right track. Rev 2.13 applied a patch intended to improve asinh and acosh, but the author mistakenly replaced the body of asin with their new code for asinh. See bug report for all the gory details. This patch: (a) puts the "new" (as of 2.13) asinh code into the asinh function; and, (b) repairs asin via what Abramowitz & Stegun say it should be (which is probably the same as what 2.12 did for asin, although I got tired of matching parentheses before being 100% sure of that -- and I don't care! The source of the old code is a mystery, and I *know* why I picked the new code.). --- Modules/cmathmodule.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/Modules/cmathmodule.c b/Modules/cmathmodule.c index cc7b1f0b2d..b961ca8f1a 100644 --- a/Modules/cmathmodule.c +++ b/Modules/cmathmodule.c @@ -67,11 +67,11 @@ static char c_acosh_doc[] = static Py_complex c_asin(Py_complex x) { - Py_complex z; - z = c_sqrt(c_half); - z = c_log(c_prod(z, c_sum(c_sqrt(c_sum(x, c_i)), - c_sqrt(c_diff(x, c_i))))); - return c_sum(z, z); + /* -i * log[(sqrt(1-x**2) + i*x] */ + const Py_complex squared = c_prod(x, x); + const Py_complex sqrt_1_minus_x_sq = c_sqrt(c_diff(c_one, squared)); + const Py_complex sum = c_sum(sqrt_1_minus_x_sq, c_prod(c_i, x)); + return c_neg(c_prodi(c_log(sum))); } static char c_asin_doc[] = @@ -83,10 +83,11 @@ static char c_asin_doc[] = static Py_complex c_asinh(Py_complex x) { - /* Break up long expression for WATCOM */ Py_complex z; - z = c_sum(c_one, c_prod(x, x)); - return c_log(c_sum(c_sqrt(z), x)); + z = c_sqrt(c_half); + z = c_log(c_prod(z, c_sum(c_sqrt(c_sum(x, c_i)), + c_sqrt(c_diff(x, c_i))))); + return c_sum(z, z); } static char c_asinh_doc[] = -- 2.50.0