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diff --git a/sys/vops/lz/aluid.x b/sys/vops/lz/aluid.x
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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<mach.h>
+
+# ALUI -- Vector lookup and interpolate (linear).  B[i] = A(X[i]).
+# No bounds checking is performed, but the case A(X[i])=NPIX (no fractional
+# part) is recognized and will not cause a reference off the right end of the
+# array.  This is done in a way which will also cause execution to be faster
+# when the sample points are integral, i.e., fall exactly on data points in
+# the input array.
+
+procedure aluid (a, b, x, npix)
+
+double	a[ARB], b[ARB]
+real	x[ARB], fraction, tol
+int	npix, i, left_pixel
+
+begin
+	tol = EPSILONR * 5.0
+
+	do i = 1, npix {
+	    left_pixel = int (x[i])
+	    fraction = x[i] - real(left_pixel)
+	    if (fraction < tol)
+		b[i] = a[left_pixel]
+	    else
+		b[i] = a[left_pixel] * (1.0 - fraction) +
+		       a[left_pixel+1] * fraction
+	}
+end