2 * (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
3 * See the copyright notice in the ACK home directory, in the file "Copyright".
5 * Author: Ceriel J.H. Jacobs
7 /* $Id: log.c,v 1.4 1994/06/24 11:43:59 ceriel Exp $ */
12 #include "localmath.h"
17 /* Algorithm and coefficients from:
18 "Software manual for the elementary functions"
19 by W.J. Cody and W. Waite, Prentice-Hall, 1980
22 -0.64124943423745581147e2,
23 0.16383943563021534222e2,
24 -0.78956112887491257267e0
27 -0.76949932108494879777e3,
28 0.31203222091924532844e3,
29 -0.35667977739034646171e2,
33 double znum, zden, z, w;
51 else return x; /* for infinity and Nan */
52 x = frexp(x, &exponent);
54 znum = (x - 0.5) - 0.5;
59 zden = znum * 0.5 + 0.5;
62 z = znum/zden; w = z * z;
63 x = z + z * w * (POLYNOM2(w,a)/POLYNOM3(w,b));
65 x += z * (-2.121944400546905827679e-4);
66 return x + z * 0.693359375;