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components/external/espruino/libs/math/isnan.c

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+/*							isnan()
+ *							signbit()
+ *							isfinite()
+ *
+ *	Floating point numeric utilities
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * double ceil(), floor(), frexp(), ldexp();
+ * int signbit(), isnan(), isfinite();
+ * double x, y;
+ * int expnt, n;
+ *
+ * y = floor(x);
+ * y = ceil(x);
+ * y = frexp( x, &expnt );
+ * y = ldexp( x, n );
+ * n = signbit(x);
+ * n = isnan(x);
+ * n = isfinite(x);
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * All four routines return a double precision floating point
+ * result.
+ *
+ * floor() returns the largest integer less than or equal to x.
+ * It truncates toward minus infinity.
+ *
+ * ceil() returns the smallest integer greater than or equal
+ * to x.  It truncates toward plus infinity.
+ *
+ * frexp() extracts the exponent from x.  It returns an integer
+ * power of two to expnt and the significand between 0.5 and 1
+ * to y.  Thus  x = y * 2**expn.
+ *
+ * ldexp() multiplies x by 2**n.
+ *
+ * signbit(x) returns 1 if the sign bit of x is 1, else 0.
+ *
+ * These functions are part of the standard C run time library
+ * for many but not all C compilers.  The ones supplied are
+ * written in C for either DEC or IEEE arithmetic.  They should
+ * be used only if your compiler library does not already have
+ * them.
+ *
+ * The IEEE versions assume that denormal numbers are implemented
+ * in the arithmetic.  Some modifications will be required if
+ * the arithmetic has abrupt rather than gradual underflow.
+ */
+
+
+/*
+Cephes Math Library Release 2.3:  March, 1995
+Copyright 1984, 1995 by Stephen L. Moshier
+*/
+
+
+#include "mconf.h"
+
+#ifdef UNK
+/* ceil(), floor(), frexp(), ldexp() may need to be rewritten. */
+#undef UNK
+#if BIGENDIAN
+#define MIEEE 1
+#else
+#define IBMPC 1
+#endif
+#endif
+
+
+/* Return 1 if the sign bit of x is 1, else 0.  */
+
+int signbit(x)
+double x;
+{
+union
+	{
+	double d;
+	short s[4];
+	int i[2];
+	} u;
+
+u.d = x;
+
+if( sizeof(int) == 4 )
+	{
+#ifdef IBMPC
+	return( u.i[1] < 0 );
+#endif
+#ifdef DEC
+	return( u.s[3] < 0 );
+#endif
+#ifdef MIEEE
+	return( u.i[0] < 0 );
+#endif
+	}
+else
+	{
+#ifdef IBMPC
+	return( u.s[3] < 0 );
+#endif
+#ifdef DEC
+	return( u.s[3] < 0 );
+#endif
+#ifdef MIEEE
+	return( u.s[0] < 0 );
+#endif
+	}
+}
+
+
+/* Return 1 if x is a number that is Not a Number, else return 0.  */
+
+int isnan(x)
+double x;
+{
+#ifdef NANS
+union
+	{
+	double d;
+	unsigned short s[4];
+	unsigned int i[2];
+	} u;
+
+u.d = x;
+
+if( sizeof(int) == 4 )
+	{
+#ifdef IBMPC
+	if( ((u.i[1] & 0x7ff00000) == 0x7ff00000)
+	    && (((u.i[1] & 0x000fffff) != 0) || (u.i[0] != 0)))
+		return 1;
+#endif
+#ifdef DEC
+	if( (u.s[1] & 0x7fff) == 0)
+		{
+		if( (u.s[2] | u.s[1] | u.s[0]) != 0 )
+			return(1);
+		}
+#endif
+#ifdef MIEEE
+	if( ((u.i[0] & 0x7ff00000) == 0x7ff00000)
+	    && (((u.i[0] & 0x000fffff) != 0) || (u.i[1] != 0)))
+		return 1;
+#endif
+	return(0);
+	}
+else
+	{ /* size int not 4 */
+#ifdef IBMPC
+	if( (u.s[3] & 0x7ff0) == 0x7ff0)
+		{
+		if( ((u.s[3] & 0x000f) | u.s[2] | u.s[1] | u.s[0]) != 0 )
+			return(1);
+		}
+#endif
+#ifdef DEC
+	if( (u.s[3] & 0x7fff) == 0)
+		{
+		if( (u.s[2] | u.s[1] | u.s[0]) != 0 )
+			return(1);
+		}
+#endif
+#ifdef MIEEE
+	if( (u.s[0] & 0x7ff0) == 0x7ff0)
+		{
+		if( ((u.s[0] & 0x000f) | u.s[1] | u.s[2] | u.s[3]) != 0 )
+			return(1);
+		}
+#endif
+	return(0);
+	} /* size int not 4 */
+
+#else
+/* No NANS.  */
+return(0);
+#endif
+}
+
+
+/* Return 1 if x is not infinite and is not a NaN.  */
+
+int isfinite(x)
+double x;
+{
+#ifdef INFINITIES
+union
+	{
+	double d;
+	unsigned short s[4];
+	unsigned int i[2];
+	} u;
+
+u.d = x;
+
+if( sizeof(int) == 4 )
+	{
+#ifdef IBMPC
+	if( (u.i[1] & 0x7ff00000) != 0x7ff00000)
+		return 1;
+#endif
+#ifdef DEC
+	if( (u.s[3] & 0x7fff) != 0)
+		return 1;
+#endif
+#ifdef MIEEE
+	if( (u.i[0] & 0x7ff00000) != 0x7ff00000)
+		return 1;
+#endif
+	return(0);
+	}
+else
+	{
+#ifdef IBMPC
+	if( (u.s[3] & 0x7ff0) != 0x7ff0)
+		return 1;
+#endif
+#ifdef DEC
+	if( (u.s[3] & 0x7fff) != 0)
+		return 1;
+#endif
+#ifdef MIEEE
+	if( (u.s[0] & 0x7ff0) != 0x7ff0)
+		return 1;
+#endif
+	return(0);
+	}
+#else
+/* No INFINITY.  */
+return(1);
+#endif
+}