Program c06fqfe

!     C06FQF Example Program Text

!     Mark 29.3 Release. NAG Copyright 2023.

!     .. Use Statements ..
      Use nag_library, Only: c06fpf, c06fqf, nag_wp
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
      Integer                          :: i, ieof, ifail, j, m, n
!     .. Local Arrays ..
      Real (Kind=nag_wp), Allocatable  :: trig(:), u(:), v(:), work(:), x(:)
!     .. Executable Statements ..
      Write (nout,*) 'C06FQF Example Program Results'
!     Skip heading in data file
      Read (nin,*)
loop: Do
        Read (nin,*,Iostat=ieof) m, n
        If (ieof<0) Then
          Exit loop
        End If

        Allocate (trig(2*n),u(n),v(n),work(2*m*n),x(m*n))
        Do j = 1, m
          Read (nin,*)(x(i*m+j),i=0,n-1)
        End Do
        Write (nout,*)
        Write (nout,*) 'Original data values'
        Write (nout,*)
        Write (nout,99999)('     ',(x(i*m+j),i=0,n-1),j=1,m)
        Write (nout,*)
        Write (nout,*) 'Original data written in full complex form'

        Do j = 1, m
          u(1:n) = x(j:m*n:m)
          v(1:n) = 0.0_nag_wp
          v(2:(n+1)/2) = u(n:n-(n-1)/2+1:-1)
          u(n:n-(n-1)/2+1:-1) = u(2:(n+1)/2)
          v(n-(n-1)/2+1:n) = -v((n+1)/2:2:-1)
          Write (nout,*)
          Write (nout,99999) 'Real ', u(1:n)
          Write (nout,99999) 'Imag ', v(1:n)
        End Do

        ifail = 0
        Call c06fqf(m,n,x,'Initial',trig,work,ifail)

        Write (nout,*)
        Write (nout,*) 'Discrete Fourier transforms (real values)'
        Write (nout,*)
        Write (nout,99999)('     ',(x(i*m+j),i=0,n-1),j=1,m)

        Call c06fpf(m,n,x,'Subsequent',trig,work,ifail)
        x((n/2+1)*m+1:m*n) = -x((n/2+1)*m+1:m*n)

        Write (nout,*)
        Write (nout,*) 'Original data as restored by inverse transform'
        Write (nout,*)
        Write (nout,99999)('     ',(x(i*m+j),i=0,n-1),j=1,m)
        Deallocate (trig,u,v,work,x)
      End Do loop

99999 Format (1X,A,6F10.4)
    End Program c06fqfe