www.pudn.com > 文件恢复及修补 C 语言源程序.zip > SQRT.C

 
/*********************************************************** 
 *               The TULSA IBM C BOARD                     * 
 *                   918-664-8737                          * 
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#include "math.h" 
#include "errno.h" 
 
double sqrt(x) 
double x; 
{ 
        double f, y; 
        int n; 
        extern int errno; 
 
        if (x == 0.0) 
                return x; 
        if (x < 0.0) { 
                errno = EDOM; 
                return 0.0; 
        } 
        f = frexp(x, &n); 
        y = 0.41731 + 0.59016 * f; 
        y = (y + f/y); 
        y = ldexp(y,-2) + f/y;  /* fast calculation of y2 */ 
        y = ldexp(y + f/y, -1); 
        y = ldexp(y + f/y, -1); 
 
        if (n&1) { 
                y *= 0.70710678118654752440; 
                ++n; 
        } 
        return ldexp(y,n/2); 
}