c===========================================================
c     vswave: Generates time-series of profiles of 
c     left-moving "wave" (f(t+x) = constant) and outputs to 
c     'vs' server.
c===========================================================
      program     vswave

      implicit    none

      integer     n
      parameter ( n = 65 )

      real*8      f
      real*8      x(n),        y(n)
      integer     i,           j,          nx,            nt
      real*8      h,           t,          dt

      nx = n
      nt = n

      h = 1.0d0 / (nx - 1)
      x(1) = 0.0d0
      do j = 1 , nx - 1
         x(j+1) = x(j) + h
      end do

      t = 0.0d0
      dt = 1.0d0 / (nt - 1)
      do i = 1 , nt
         do j = 1 , nx 
c-----------------------------------------------------------
c           Define y(x,t)
c-----------------------------------------------------------
            y(j) = f(mod((x(j) + t),1.0d0))
         end do
c-----------------------------------------------------------
c        Transmit data to server 
c-----------------------------------------------------------
         call vsxynt('vswave',t,x,y,nx)
         t = t + dt 
      end do

      stop

      end

c-----------------------------------------------------------
c     Gaussian function.
c-----------------------------------------------------------
      double precision function f(x)
         implicit      none
         real*8        x
         f = exp(-((x-0.5d0)/0.1d0)**2)
         return
      end