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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+# AFFTRR -- Forward fourier transform (real transform, real output arrays).
+# The forward transform of the real array SR length NPIX is computed and
+# returned in the real arrays FR and FI of length NPIX/2+1.  Since the real
+# 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 afftrr (sr, si, fr, fi, npix)
+
+real	sr[ARB], si[ARB]	# spatial data (input).  SI NOT USED.
+real	fr[ARB], fi[ARB]	# real and imag parts of transform (output)
+int	npix
+int	ier
+pointer	sp, work
+
+begin
+	call smark (sp)
+	call salloc (work, npix + 2, TY_REAL)
+
+	# Copy the real data vector into the work array.
+	call amovr (sr, Memr[work], npix)
+
+	# Compute the forward transform.
+	call ffa (Memr[work], npix, ier)
+	if (ier == 1)
+	    call fatal (1, "afftrr: npix not a power of 2")
+
+	# Unpack the real and imaginary parts into the output arrays.
+	call aupxr (Memr[work], fr, fi, npix / 2 + 1)
+
+	call sfree (sp)
+end