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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
# AIFTXX -- Inverse fourier transform (complex transform, complex array).
# The fourier transform of the complex array A of length NPIX pixels is
# computed and the NPIX complex data points are returned in the complex array
# B. The transformation may be performed in place if desired. NPIX must be
# a power of 2.
#
# N.B.: The Fortran 77 standard guarantees that a complex datum is represented
# as two reals, and that the first real in storage order is the real part of
# the complex datum and the second real the imaginary part. We have defined
# A and B to be type COMPLEX arrays in the calling program, but FFT842 expects
# a REAL array containing (real,imag) pairs. The Fortran standard appears to
# guarantee that this will work.
procedure aiftxx (a, b, npix)
complex a[ARB] # transform (input)
complex b[ARB] # data (output)
int npix
int ier
pointer sp, xr, xi
begin
call smark (sp)
call salloc (xr, npix, TY_REAL)
call salloc (xi, npix, TY_REAL)
# Rearrange the elements of the A array as required by FFT842.
# Convert the array A of complex values into an array of reals
# and an array of imaginaries.
call aupxr (a, Memr[xr], Memr[xi], npix)
# Compute the inverse transform.
call fft842 (1, npix, Memr[xr], Memr[xi], ier)
if (ier == 1)
call fatal (1, "afftxx: npix not a power of 2")
# Repack the real and imaginary arrays to form the complex output
# array.
call apkxr (Memr[xr], Memr[xi], b, npix)
call sfree (sp)
end
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