debian man page for zrotg

ZROTG(3)							   BLAS routine 							  ZROTG(3)

NAME
       ZROTG - construct givens plane rotation

SYNOPSIS
       subroutine zrotg(ca,cb,c,s)

	   double		   complex ca,cb,s

	   double		   precision c

	   double		   precision norm,scale

	   double		   complex alpha

	   if			   (cdabs(ca) .ne. 0.0d0) go to 10

	   c			   = 0.0d0

	   s			   = (1.0d0,0.0d0)

	   ca			   = cb

	   go			   to 20

	   10			   continue

	   scale		   = cdabs(ca) + cdabs(cb)

	   norm 		   = scale*dsqrt((cdabs(ca/dcmplx(scale,0.0d0)))**2 +

	   *			   (cdabs(cb/dcmplx(scale,0.0d0)))**2)

	   alpha		   = ca /cdabs(ca)

	   c			   = cdabs(ca) / norm

	   s			   = alpha * dconjg(cb) / norm

	   ca			   = alpha * norm

	   20			   continue

	   return

	   end

PURPOSE
BLAS routine							  16 October 1992							  ZROTG(3)