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