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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+# ADVZ -- Vector divide with checking for zero divisors.  If the result of a
+# divide would be undefined a user supplied function is called to get the
+# output pixel value.
+#
+# NOTE: in the interests of simplicity a somewhat arbitrary tolerance is used
+# to check for an undefined divide, i.e., a divide by zero or a divide by a
+# number small enough to cause floating point overflow.  A better way to do
+# this would be to provide a machine dependent version of this operator in
+# host$as which catches the hardware exception rather than using a comparison.
+
+procedure advzi (a, b, c, npix, errfcn)
+
+int	a[ARB], b[ARB], c[ARB]	# numerator, divisor, and output arrays
+int	npix			# number of pixels
+int	errfcn()		# user function, called on divide by zero
+
+int	i
+int	divisor
+extern	errfcn()
+errchk	errfcn
+
+begin
+
+	do i = 1, npix {
+	    divisor = b[i]
+		if (divisor == 0)
+		    c[i] = errfcn (a[i])
+		else
+		    c[i] = a[i] / divisor
+	}
+end