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132 lines
3.1 KiB
C
132 lines
3.1 KiB
C
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/* @(#)s_modf.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/*
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FUNCTION
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<<modf>>, <<modff>>---split fractional and integer parts
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INDEX
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modf
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INDEX
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modff
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ANSI_SYNOPSIS
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#include <math.h>
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double modf(double <[val]>, double *<[ipart]>);
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float modff(float <[val]>, float *<[ipart]>);
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TRAD_SYNOPSIS
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#include <math.h>
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double modf(<[val]>, <[ipart]>)
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double <[val]>;
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double *<[ipart]>;
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float modff(<[val]>, <[ipart]>)
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float <[val]>;
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float *<[ipart]>;
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DESCRIPTION
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<<modf>> splits the double <[val]> apart into an integer part
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and a fractional part, returning the fractional part and
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storing the integer part in <<*<[ipart]>>>. No rounding
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whatsoever is done; the sum of the integer and fractional
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parts is guaranteed to be exactly equal to <[val]>. That
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is, if <[realpart]> = modf(<[val]>, &<[intpart]>); then
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`<<<[realpart]>+<[intpart]>>>' is the same as <[val]>.
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<<modff>> is identical, save that it takes and returns
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<<float>> rather than <<double>> values.
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RETURNS
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The fractional part is returned. Each result has the same
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sign as the supplied argument <[val]>.
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PORTABILITY
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<<modf>> is ANSI C. <<modff>> is an extension.
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QUICKREF
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modf ansi pure
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modff - pure
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*/
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/*
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* modf(double x, double *iptr)
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* return fraction part of x, and return x's integral part in *iptr.
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* Method:
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* Bit twiddling.
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*
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* Exception:
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* No exception.
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*/
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#include "fdlibm.h"
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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static const double one = 1.0;
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#else
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static double one = 1.0;
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#endif
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#ifdef __STDC__
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double modf(double x, double *iptr)
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#else
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double modf(x, iptr)
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double x,*iptr;
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#endif
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{
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__int32_t i0,i1,j0;
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__uint32_t i;
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EXTRACT_WORDS(i0,i1,x);
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j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
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if(j0<20) { /* integer part in high x */
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if(j0<0) { /* |x|<1 */
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INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */
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return x;
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} else {
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i = (0x000fffff)>>j0;
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if(((i0&i)|i1)==0) { /* x is integral */
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__uint32_t high;
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*iptr = x;
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GET_HIGH_WORD(high,x);
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INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
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return x;
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} else {
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INSERT_WORDS(*iptr,i0&(~i),0);
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return x - *iptr;
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}
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}
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} else if (j0>51) { /* no fraction part */
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__uint32_t high;
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*iptr = x*one;
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GET_HIGH_WORD(high,x);
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INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
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return x;
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} else { /* fraction part in low x */
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i = ((__uint32_t)(0xffffffff))>>(j0-20);
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if((i1&i)==0) { /* x is integral */
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__uint32_t high;
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*iptr = x;
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GET_HIGH_WORD(high,x);
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INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
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return x;
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} else {
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INSERT_WORDS(*iptr,i0,i1&(~i));
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return x - *iptr;
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}
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}
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}
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#endif /* _DOUBLE_IS_32BITS */
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