!   C06PFF Example Program Text
!   Mark 23 Release. NAG Copyright 2011.

    MODULE c06pffe_mod

!      C06PFF Example Program Module:
!             Parameters and User-defined Routines

!      .. Use Statements ..
       USE nag_library, ONLY : nag_wp
!      .. Implicit None Statement ..
       IMPLICIT NONE
!      .. Parameters ..
       INTEGER, PARAMETER                  :: nin = 5, nout = 6
    CONTAINS
       SUBROUTINE readx(nin,x,n1,n2)
!         Read 2-dimensional complex data

!         .. Implicit None Statement ..
          IMPLICIT NONE
!         .. Scalar Arguments ..
          INTEGER, INTENT (IN)                :: n1, n2, nin
!         .. Array Arguments ..
          COMPLEX (KIND=nag_wp), INTENT (OUT) :: x(n1,n2)
!         .. Local Scalars ..
          INTEGER                             :: i, j
!         .. Executable Statements ..
          DO i = 1, n1
             READ (nin,*) (x(i,j),j=1,n2)
          END DO
          RETURN
       END SUBROUTINE readx

       SUBROUTINE writx(nout,x,n1,n2)
!         Print 2-dimensional complex data

!         .. Implicit None Statement ..
          IMPLICIT NONE
!         .. Scalar Arguments ..
          INTEGER, INTENT (IN)                :: n1, n2, nout
!         .. Array Arguments ..
          COMPLEX (KIND=nag_wp), INTENT (IN)  :: x(n1,n2)
!         .. Local Scalars ..
          INTEGER                             :: i, j
!         .. Executable Statements ..
          DO i = 1, n1
             WRITE (nout,*)
             WRITE (nout,99999) (x(i,j),j=1,n2)
          END DO
          RETURN

99999     FORMAT (1X,7(:1X,'(',F6.3,',',F6.3,')'))
       END SUBROUTINE writx
    END MODULE c06pffe_mod

    PROGRAM c06pffe

!      C06PFF Example Main Program

!      .. Use Statements ..
       USE nag_library, ONLY : c06pff, nag_wp
       USE c06pffe_mod, ONLY : nin, nout, readx, writx
!      .. Implicit None Statement ..
       IMPLICIT NONE
!      .. Local Scalars ..
       INTEGER                             :: ieof, ifail, l, lwork, n, ndim
!      .. Local Arrays ..
       COMPLEX (KIND=nag_wp), ALLOCATABLE  :: work(:), x(:)
       INTEGER, ALLOCATABLE                :: nd(:)
!      .. Intrinsic Functions ..
       INTRINSIC                              product
!      .. Executable Statements ..
       WRITE (nout,*) 'C06PFF Example Program Results'
!      Skip heading in data file
       READ (nin,*)
LOOP:  DO
          READ (nin,*,IOSTAT=ieof) ndim
          IF (ieof<0) EXIT LOOP
          ALLOCATE (nd(ndim))
          READ (nin,*) nd(1:ndim), l
          n = product(nd(1:ndim))
          lwork = n + nd(l) + 15
          ALLOCATE (x(n),work(lwork))
          CALL readx(nin,x,nd(1),nd(2))
          WRITE (nout,*)
          WRITE (nout,*) 'Original data'
          CALL writx(nout,x,nd(1),nd(2))

!         ifail: behaviour on error exit   
!                =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
          ifail = 0
!         Compute transform
          CALL c06pff('F',ndim,l,nd,n,x,work,lwork,ifail)

          WRITE (nout,*)
          WRITE (nout,99999) 'Discrete Fourier transform of variable ', l
          CALL writx(nout,x,nd(1),nd(2))

!         Compute inverse transform
          CALL c06pff('B',ndim,l,nd,n,x,work,lwork,ifail)

          WRITE (nout,*)
          WRITE (nout,*) 'Original sequence as restored by inverse transform'
          CALL writx(nout,x,nd(1),nd(2))
          DEALLOCATE (nd,x,work)

       END DO LOOP

99999  FORMAT (1X,A,I1)
    END PROGRAM c06pffe