libf2c/libF77/c_sqrt.c

   1 #include "f2c.h"
   2
   3 #ifdef KR_headers
   4 extern double sqrt(), f__cabs();
   5
   6 VOID c_sqrt(r, z) complex *r, *z;
   7 #else
   8 #undef abs
   9 #include "math.h"
  10 extern double f__cabs(double, double);
  11
  12 void c_sqrt(complex *r, complex *z)
  13 #endif
  14 {
  15         double mag, t;
  16         double zi = z->i, zr = z->r;
  17
  18         if( (mag = f__cabs(zr, zi)) == 0.)
  19                 r->r = r->i = 0.;
  20         else if(zr > 0)
  21                 {
  22                 r->r = t = sqrt(0.5 * (mag + zr) );
  23                 t = zi / t;
  24                 r->i = 0.5 * t;
  25                 }
  26         else
  27                 {
  28                 t = sqrt(0.5 * (mag - zr) );
  29                 if(zi < 0)
  30                         t = -t;
  31                 r->i = t;
  32                 t = zi / t;
  33                 r->r = 0.5 * t;
  34                 }
  35         }