1 /* expf.c: Computes e**x 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 */
28 #define P0 0.2499999995E+0
29 #define P1 0.4160288626E-2
30 #define Q0 0.5000000000E+0
31 #define Q1 0.4998717877E-1
33 #define P(z) ((P1*z)+P0)
34 #define Q(z) ((Q1*z)+Q0)
36 #define C1 0.693359375
37 #define C2 -2.1219444005469058277e-4
39 #define BIGX 88.72283911 /* ln(XMAX) */
40 #define EXPEPS 1.0E-7 /* exp(1.0E-7)=0.0000001 */
41 #define K1 1.4426950409 /* 1/ln(2) */
43 float expf(const float x)
54 if(y<EXPEPS) return 1.0;