pow.c

上一个上传的有问题,这个是好的。visopsys包括系统内核和GUI的全部SOURCE code ,还包括一些基本的docs文档。里面src子目录对应所有SOURCE code.对于想研究操作系统的朋

// 
//  Visopsys
//  Copyright (C) 1998-2007 J. Andrew McLaughlin
//  
//  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.
//
//  pow.c
//

// This is the standard "pow" function, as found in standard C libraries

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


double pow(double x, double y)
{
  // The pow() function returns the value of x raised to the power of y.

  int count;

  if ((x < 0) && (floor(y) != y))
    {
      // The argument x is negative and y is not an integral value.  This
      // would result in a complex number.
      errno = ERR_DOMAIN;
      return (0);
    }

  if (y == 0)
    x = 1;
  else
    {
      for (count = 1; count < y; count ++)
	x *= x;
    }

  return (x);
}