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diff --git a/funtools/util/NaN.h.in b/funtools/util/NaN.h.in
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+/*
+ *	Copyright (c) 1999-2003 Smithsonian Astrophysical Observatory
+ */
+
+/*
+ *
+ * NaN.h -- include file to deal with IEEE NaN values
+ *
+ * Idea taken from fitsio2.h in the cfitsio package by William Pence (HEASARC),
+ * to whom grateful acknowledgement is made.
+ *
+ * These functions tests whether the float value is a reserved IEEE
+ * value such as a Not-a-Number (NaN), or underflow, overflow, or
+ * infinity.   The functions returns 1 if the value is a NaN, overflow
+ * or infinity; otherwise it returns 0.
+ *
+ * isnanf tests floats, isnand tests doubles.
+ *
+ */
+#ifndef	__nan_h
+#define	__nan_h
+
+#include "prsetup.h"
+
+#define _BIG_ENDIAN @BIGENDIAN@
+
+#if _BIG_ENDIAN
+
+#define FNANOFF 0
+#define DNANOFF 0
+
+#else
+
+#define FNANOFF 1
+#define DNANOFF 3
+
+#endif
+
+#define FNANMASK   0x7F80 /* mask bits 1 - 8; all set on NaNs */
+                                     /* all 0 on underflow  or 0. */
+ 
+#define DNANMASK   0x7FF0 /* mask bits 1 - 11; all set on NaNs */
+                                     /* all 0 on underflow  or 0. */
+ 
+#ifndef isnanf
+typedef union {
+  float f; 
+  short x[2];
+} uffu;
+
+#define isnanf(X) ((((uffu*)&X)->x[FNANOFF] & FNANMASK) == FNANMASK)
+#endif
+
+#ifndef isnand
+typedef union {
+  double d;
+  short x[4];
+} uddu;
+
+#define isnand(X) ((((uddu*)&X)->x[DNANOFF] & DNANMASK) == DNANMASK)
+#endif
+ 
+_PRbeg
+
+float  getnanf _PRx((void));
+double getnand _PRx((void));
+
+_PRend
+
+#endif