powf.c

sdcc是为51等小型嵌入式cpu设计的c语言编译器支持数种不同类型的cpu

/*  powf.c:  Computes x**y where x and y are 32-bit floats.
             WARNING: less that 6 digits accuracy.

    Copyright (C) 2001, 2002  Jesus Calvino-Fraga, [e-mail] 

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA */

/* Version 1.0 - Initial release */

/*
** $Id: powf.c 3654 2005-01-24 10:38:53Z vrokas $
*/

#include <math.h>
#include <errno.h>

float powf(const float x, const float y)
{
    if(y == 0.0) return 1.0;
    if(y==1.0) return x;
    if(x <= 0.0) return 0.0;
    return expf(logf(x) * y);
}