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subroutine zdrot (n,zx,incx,zy,incy,c,s)
c
c applies a plane rotation, where the cos and sin (c and s) are
c double precision and the vectors zx and zy are double complex.
c jack dongarra, linpack, 3/11/78.
c
double complex zx(1),zy(1),ztemp
double precision c,s
integer i,incx,incy,ix,iy,n
c
if(n.le.0)return
if(incx.eq.1.and.incy.eq.1)go to 20
c
c code for unequal increments or equal increments not equal
c to 1
c
ix = 1
iy = 1
if(incx.lt.0)ix = (-n+1)*incx + 1
if(incy.lt.0)iy = (-n+1)*incy + 1
do 10 i = 1,n
ztemp = c*zx(ix) + s*zy(iy)
zy(iy) = c*zy(iy) - s*zx(ix)
zx(ix) = ztemp
ix = ix + incx
iy = iy + incy
10 continue
return
c
c code for both increments equal to 1
c
20 do 30 i = 1,n
ztemp = c*zx(i) + s*zy(i)
zy(i) = c*zy(i) - s*zx(i)
zx(i) = ztemp
30 continue
return
end
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