*     C06PXF Example Program Text.
*     Mark 19 Release. NAG Copyright 1999.
*     .. Parameters ..
      INTEGER          NIN, NOUT
      PARAMETER        (NIN=5,NOUT=6)
      INTEGER          N1MAX, N2MAX, N3MAX, NMAX, LWORK
      PARAMETER        (N1MAX=16,N2MAX=16,N3MAX=16,
     +                 NMAX=N1MAX*N2MAX*N3MAX,LWORK=N1MAX+N2MAX+N3MAX+
     +                 NMAX+45)
*     .. Local Scalars ..
      INTEGER          IFAIL, N, N1, N2, N3
*     .. Local Arrays ..
      COMPLEX *16      WORK(LWORK), X(NMAX)
*     .. External Subroutines ..
      EXTERNAL         C06PXF, READX, WRITX
*     .. Executable Statements ..
      WRITE (NOUT,*) 'C06PXF Example Program Results'
*     Skip heading in data file
      READ (NIN,*)
   20 CONTINUE
      READ (NIN,*,END=40) N1, N2, N3
      N = N1*N2*N3
      IF (N.GE.1 .AND. N.LE.NMAX) THEN
         CALL READX(NIN,X,N1,N2,N3)
         WRITE (NOUT,*)
         WRITE (NOUT,*) 'Original data values'
         CALL WRITX(NOUT,X,N1,N2,N3)
         IFAIL = 0
*
*        -- Compute transform
         CALL C06PXF('F',N1,N2,N3,X,WORK,IFAIL)
*
         WRITE (NOUT,*)
         WRITE (NOUT,*) 'Components of discrete Fourier transform'
         CALL WRITX(NOUT,X,N1,N2,N3)
*
*        -- Compute inverse transform
         CALL C06PXF('B',N1,N2,N3,X,WORK,IFAIL)
*
         WRITE (NOUT,*)
         WRITE (NOUT,*)
     +     'Original sequence as restored by inverse transform'
         CALL WRITX(NOUT,X,N1,N2,N3)
         GO TO 20
      ELSE
         WRITE (NOUT,*) ' ** Invalid value of N1, N2 or N3'
      END IF
   40 CONTINUE
      STOP
      END
*
      SUBROUTINE READX(NIN,X,N1,N2,N3)
*     Read 3-dimensional complex data
*     .. Scalar Arguments ..
      INTEGER          N1, N2, N3, NIN
*     .. Array Arguments ..
      COMPLEX *16      X(N1,N2,N3)
*     .. Local Scalars ..
      INTEGER          I, J, K
*     .. Executable Statements ..
      DO 40 I = 1, N1
         DO 20 J = 1, N2
            READ (NIN,*) (X(I,J,K),K=1,N3)
   20    CONTINUE
   40 CONTINUE
      RETURN
      END
*
      SUBROUTINE WRITX(NOUT,X,N1,N2,N3)
*     Print 3-dimensional complex data
*     .. Scalar Arguments ..
      INTEGER          N1, N2, N3, NOUT
*     .. Array Arguments ..
      COMPLEX *16      X(N1,N2,N3)
*     .. Local Scalars ..
      INTEGER          I, J, K
*     .. Intrinsic Functions ..
      INTRINSIC        DBLE, DIMAG
*     .. Executable Statements ..
      DO 40 I = 1, N1
         WRITE (NOUT,*)
         WRITE (NOUT,99998) 'z(i,j,k) for i =', I
         DO 20 J = 1, N2
            WRITE (NOUT,*)
            WRITE (NOUT,99999) 'Real ', (DBLE(X(I,J,K)),K=1,N3)
            WRITE (NOUT,99999) 'Imag ', (DIMAG(X(I,J,K)),K=1,N3)
   20    CONTINUE
   40 CONTINUE
      RETURN
*
99999 FORMAT (1X,A,7F10.3,/(6X,7F10.3))
99998 FORMAT (1X,A,I6)
      END