gcc/libf2c/libF77/c_sqrt.c

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#include "f2c.h"
#ifdef KR_headers
extern double sqrt(), f__cabs();
VOID c_sqrt(resx, z) complex *resx, *z;
#else
#undef abs
#include <math.h>
extern double f__cabs(double, double);
void c_sqrt(complex *resx, complex *z)
#endif
{
double mag, t;
complex res;
if( (mag = f__cabs(z->r, z->i)) == 0.)
res.r = res.i = 0.;
else if(z->r > 0)
{
res.r = t = sqrt(0.5 * (mag + z->r) );
t = z->i / t;
res.i = 0.5 * t;
}
else
{
t = sqrt(0.5 * (mag - z->r) );
if(z->i < 0)
t = -t;
res.i = t;
t = z->i / t;
res.r = 0.5 * t;
}
resx->r = res.r;
resx->i = res.i;
}