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C/C++ Source or Header  |  1994-03-20  |  505 b   |  35 lines
  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.  
  17. if( (mag = f__cabs(z->r, z->i)) == 0.)
  18.     r->r = r->i = 0.;
  19. else if(z->r > 0)
  20.     {
  21.     r->r = t = sqrt(0.5 * (mag + z->r) );
  22.     t = z->i / t;
  23.     r->i = 0.5 * t;
  24.     }
  25. else
  26.     {
  27.     t = sqrt(0.5 * (mag - z->r) );
  28.     if(z->i < 0)
  29.         t = -t;
  30.     r->i = t;
  31.     t = z->i / t;
  32.     r->r = 0.5 * t;
  33.     }
  34. }
  35.