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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
# AIFTRR -- Inverse fourier transform (real transform, real output arrays).
# The inverse transform of the real arrays FR and FI of length NPIX/2+1 is
# returned in the real array SR of length NPIX. Since the real inverse
# transform is being performed the array SI is ignored and may be omitted.
# The transformation may be performed in place if desired. NPIX must be a
# power of 2.
procedure aiftrr (fr, fi, sr, si, npix)
real fr[ARB], fi[ARB] # real and imag parts of transform (input)
real sr[ARB], si[ARB] # spatial data (output). SI NOT USED.
int npix
int ier
pointer sp, work
begin
call smark (sp)
call salloc (work, npix + 2, TY_REAL)
# Pack the real and imaginary parts into a complex array as required
# by FFS.
call apkxr (fr, fi, Memr[work], npix / 2 + 1)
# Compute the inverse transform.
call ffs (Memr[work], npix, ier)
if (ier == 1)
call fatal (1, "aiftrr: npix not a power of 2")
# The work array now contains the real part of the transform; merely
# copy it to the output array.
call amovr (Memr[work], sr, npix)
call sfree (sp)
end
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