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Diffstat (limited to 'libm/double/isnan.c')
| -rw-r--r-- | libm/double/isnan.c | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/libm/double/isnan.c b/libm/double/isnan.c new file mode 100644 index 000000000..8ae83bcba --- /dev/null +++ b/libm/double/isnan.c @@ -0,0 +1,237 @@ +/* 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 <math.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 +} |