!-------------------------------------- LICENCE BEGIN ------------------------------------
!Environment Canada - Atmospheric Science and Technology License/Disclaimer,
!                     version 3; Last Modified: May 7, 2008.
!This is free but copyrighted software; you can use/redistribute/modify it under the terms
!of the Environment Canada - Atmospheric Science and Technology License/Disclaimer
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!See the above mentioned License/Disclaimer for more details.
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!

      subroutine qsft8( r, a, inc, jump, lot, isign, n ) 2

C
      implicit none
#include "taglam4d.cdk"
C
      integer inc, jump, lot, isign, n
      real*8  r(*), a(*)
C
      integer i, j, k, km
C
      real*8 zero, half, one, two
      parameter( zero = 0.0 )
      parameter( half = 0.5 )
      parameter( one  = 1.0 )
      parameter( two  = 2.0 )

      real*8 del, angle, ss, fac
      integer ij
      ij(i,j) = 1 + ( j - 1 ) * jump + i * inc

      del   = acos( - one )/n
C
C     The transform  is along the i-th direction
C     and the indexing is 1+(j-1)*jump+    i*inc (i=0,n-1,j=1,lot)
C                      or 1+(j-1)*jump+(k-1)*inc (k=1,  n,j=1,lot)
C     in gridpoint and Fourier space respectively
C
      if ( isign .eq. -1 ) then
C
C     transform from gridpoint to fourier
C
         fac = one/n

         do k=n,1,-1
            km = k - 1

            do j=1,lot
               r( ij(km,j) ) = zero
            enddo

            angle =  k * del

            do i=0,n-1

               ss =  sin( ( i + half ) * angle )

               do j=1,lot
                  r( ij(km,j) ) = r( ij(km,j) ) + ss * a( ij(i,j) )
               enddo

            enddo

            do j=1,lot
               r( ij(km,j) ) = fac * r( ij(km,j) )
            enddo

            fac = two/n

         enddo
         
      elseif( isign .eq. +1 ) then
C
C     transform from Fourier to gridpoint
C
         do i=0,n-1

            do j=1,lot
               r( ij(i,j) ) = zero
            enddo
 
            angle = ( i + half ) * del

            do k=1,n
               km = k - 1

               ss =  sin( k * angle )

               do j=1,lot
                  r( ij(i,j) ) = r( ij(i,j) ) + ss * a( ij(km,j) )
               enddo

            enddo

         enddo

      endif

      return
      end