1 files changed, 75 insertions, 0 deletions
diff --git a/noao/twodspec/apextract/apnearest.x b/noao/twodspec/apextract/apnearest.x
new file mode 100644
index 00000000..f3e027c5
--- /dev/null
+++ b/noao/twodspec/apextract/apnearest.x
@@ -0,0 +1,75 @@
+include	<mach.h>
+include	"apertures.h"
+
+# AP_NEAREST -- Find the index of the aperture nearest cursor position x.
+
+define	DELTA	0.01		# Tolerance for equidistant apertures
+
+procedure ap_nearest (index, line, aps, naps, x)
+
+int	index			# Index of aperture nearest x
+int	line			# Dispersion line
+pointer	aps[ARB]		# Aperture pointers
+int	naps			# Number of apertures
+real	x			# Point nearest aperture
+
+int	i, j, apaxis
+char	ch
+real	d, delta
+pointer	ap
+
+int	fscan(), nscan()
+real	ap_cveval()
+
+begin
+	if (naps == 0)
+	    return
+
+	index = 0
+	delta = MAX_REAL
+
+	for (i = 1; i <= naps; i = i + 1) {
+	    ap = aps[i]
+	    apaxis = AP_AXIS(ap)
+	    d = abs (AP_CEN(ap, apaxis)+ap_cveval(AP_CV(ap),real(line))-x)
+	    if (d < delta - DELTA) {
+		j = 1
+		index = i
+		delta = d
+	    } else if (d < delta + DELTA)
+		j = j + 1
+	}
+
+	# If there is more than one aperture equally near ask the user.
+	if (j > 1) {
+	    call printf ("Apertures")
+	    for (i = 1; i <= naps; i = i + 1) {
+	        ap = aps[i]
+	        apaxis = AP_AXIS(ap)
+	        d = abs (AP_CEN(ap, apaxis)+ap_cveval(AP_CV(ap),real(line))-x)
+	        if (d < delta + DELTA) {
+		    call printf (" %d")
+			call pargi (AP_ID (ap))
+		}
+	    }
+	    call printf (" are equally near the cursor.\n")
+10	    call printf ("Choose an aperture (%d): ")
+		call pargi (AP_ID (aps[index]))
+	    call flush (STDOUT)
+	    if (fscan (STDIN) != EOF) {
+		call scanc (ch)
+		if (ch == '\n')
+		    return
+
+		call reset_scan()
+		call gargi (j)
+		if (nscan() == 0)
+		    goto 10
+		for (i=1; (i<=naps)&&(AP_ID(aps[i])!=j); i=i+1)
+		    ;
+		if (i > naps)
+		    goto 10
+		index = i
+	    }
+	}
+end