share/lapack/blas/fortran/zrotg.f

   1       subroutine zrotg(ca,cb,c,s)
   2       double complex ca,cb,s
   3       double precision c
   4       double precision norm,scale
   5       double complex alpha
   6       if (cdabs(ca) .ne. 0.0d0) go to 10
   7          c = 0.0d0
   8          s = (1.0d0,0.0d0)
   9          ca = cb
  10          go to 20
  11    10 continue
  12          scale = cdabs(ca) + cdabs(cb)
  13          norm = scale*dsqrt((cdabs(ca/dcmplx(scale,0.0d0)))**2 +
  14      *                      (cdabs(cb/dcmplx(scale,0.0d0)))**2)
  15          alpha = ca /cdabs(ca)
  16          c = cdabs(ca) / norm
  17          s = alpha * dconjg(cb) / norm
  18          ca = alpha * norm
  19    20 continue
  20       return
  21       end