SUBROUTINE CSWAP(N,CX,INCX,CY,INCY)
 
exchanges two vectors.
 
N      Input, INTEGER N, number of elements in vectors.
 
CX     Input/output, COMPLEX CX(N).
 
INCX   Input, INTEGER INCX, increment between elements of CX.  For contiguous
       elements, INCX = 1.
 
CY     Input/output, COMPLEX CY(N).
 
INCY   Input, INTEGER INCY, increment between elements of CY.  For contiguous
       elements, INCY = 1.