1 /* logf.c: Computes the natural log of a 32 bit float as outlined in [1].
3 Copyright (C) 2001, 2002 Jesus Calvino-Fraga, jesusc@ieee.org
5 This library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 This library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with this library; if not, write to the Free Software
17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
19 /* [1] William James Cody and W. M. Waite. _Software manual for the
20 elementary functions_, Englewood Cliffs, N.J.:Prentice-Hall, 1980. */
22 /* Version 1.0 - Initial release */
27 /*Constans for 24 bits or less (8 decimal digits)*/
28 #define A0 -0.5527074855E+0
29 #define B0 -0.6632718214E+1
33 #define C0 0.70710678118654752440
34 #define C1 0.693359375 /*355.0/512.0*/
35 #define C2 -2.121944400546905827679E-4
37 float logf(const float x) _FLOAT_FUNC_REENTRANT
39 #if defined(SDCC_mcs51) && defined(SDCC_MODEL_SMALL) \
40 && !defined(SDCC_NOOVERLAY)
44 float f, z, w, znum, zden, xn;
69 return ((xn*C2+Rz)+xn*C1);