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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
# AIFTRX -- Inverse discreet fourier transform (real transform, complex data
# array in). The input array A of length NPIX/2+1 contains the DC term and
# the NPIX/2 (real,imag) pairs for each of the NPIX/2 harmonics of the real
# transform. Upon output array B contains the NPIX real data pixels from the
# inverse transform. The transform may be performed in place if desired.
#
# 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
# B to be a type COMPLEX array in the calling program, but FFS expects a
# REAL array containing (real,imag) pairs. The Fortran standard appears to
# guarantee that this will work.
procedure aiftrx (a, b, npix)
complex a[ARB] # transform, npix/2+1 elements
real b[ARB] # output data array
int npix
int ier
begin
# The following is a no-op if A and B are the same array.
call amovx (a, b, npix / 2 + 1)
# Compute the inverse real transform.
call ffs (b, npix, ier)
if (ier == 1)
call fatal (1, "afftrx: npix not a power of 2")
end
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