z_sqrt.c

DTMK软件开发包,此为开源软件,是一款很好的医学图像开发资源.

#include "v3p_f2c.h"

#ifdef KR_headers
double sqrt(), f__cabs();
VOID z_sqrt(r, z) doublecomplex *r, *z;
#else
#undef abs
#include "math.h"
#ifdef __cplusplus
extern "C" {
#endif
extern double f__cabs(double, double);
void z_sqrt(doublecomplex *r, doublecomplex *z)
#endif
{
        double mag, zi = z->i, zr = z->r;

        if( (mag = f__cabs(zr, zi)) == 0.)
                r->r = r->i = 0.;
        else if(zr > 0)
                {
                r->r = sqrt(0.5 * (mag + zr) );
                r->i = zi / r->r / 2;
                }
        else
                {
                r->i = sqrt(0.5 * (mag - zr) );
                if(zi < 0)
                        r->i = - r->i;
                r->r = zi / r->i / 2;
                }
        }
#ifdef __cplusplus
}
#endif