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[/] [or1k/] [trunk/] [newlib/] [newlib/] [libm/] [math/] [s_nextafter.c] - Blame information for rev 39

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1 39 lampret
 
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/* @(#)s_nextafter.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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       <<nextafter>>, <<nextafterf>>---get next number
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INDEX
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        nextafter
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INDEX
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        nextafterf
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ANSI_SYNOPSIS
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       #include <math.h>
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       double nextafter(double <[val]>, double <[dir]>);
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       float nextafterf(float <[val]>, float <[dir]>);
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TRAD_SYNOPSIS
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       #include <math.h>
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       double nextafter(<[val]>, <[dir]>)
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              double <[val]>;
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              double <[exp]>;
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       float nextafter(<[val]>, <[dir]>)
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              float <[val]>;
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              float <[dir]>;
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DESCRIPTION
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<<nextafter>> returns the double) precision floating point number
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closest to <[val]> in the direction toward <[dir]>.  <<nextafterf>>
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performs the same operation in single precision.  For example,
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<<nextafter(0.0,1.0)>> returns the smallest positive number which is
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representable in double precision.
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RETURNS
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Returns the next closest number to <[val]> in the direction toward
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<[dir]>.
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PORTABILITY
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        Neither <<nextafter>> nor <<nextafterf>> is required by ANSI C
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        or by the System V Interface Definition (Issue 2).
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*/
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/* IEEE functions
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 *      nextafter(x,y)
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 *      return the next machine floating-point number of x in the
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 *      direction toward y.
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 *   Special cases:
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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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        double nextafter(double x, double y)
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#else
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        double nextafter(x,y)
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        double x,y;
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#endif
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{
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        __int32_t       hx,hy,ix,iy;
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        __uint32_t lx,ly;
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        EXTRACT_WORDS(hx,lx,x);
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        EXTRACT_WORDS(hy,ly,y);
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        ix = hx&0x7fffffff;             /* |x| */
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        iy = hy&0x7fffffff;             /* |y| */
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        if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
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           ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0))     /* y is nan */
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           return x+y;
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        if(x==y) return x;              /* x=y, return x */
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        if((ix|lx)==0) {                 /* x == 0 */
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            INSERT_WORDS(x,hy&0x80000000,1);    /* return +-minsubnormal */
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            y = x*x;
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            if(y==x) return y; else return x;   /* raise underflow flag */
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        }
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        if(hx>=0) {                              /* x > 0 */
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            if(hx>hy||((hx==hy)&&(lx>ly))) {    /* x > y, x -= ulp */
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                if(lx==0) hx -= 1;
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                lx -= 1;
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            } else {                            /* x < y, x += ulp */
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                lx += 1;
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                if(lx==0) hx += 1;
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            }
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        } else {                                /* x < 0 */
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            if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
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                if(lx==0) hx -= 1;
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                lx -= 1;
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            } else {                            /* x > y, x += ulp */
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                lx += 1;
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                if(lx==0) hx += 1;
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            }
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        }
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        hy = hx&0x7ff00000;
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        if(hy>=0x7ff00000) return x+x;  /* overflow  */
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        if(hy<0x00100000) {             /* underflow */
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            y = x*x;
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            if(y!=x) {          /* raise underflow flag */
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                INSERT_WORDS(y,hx,lx);
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                return y;
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            }
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        }
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        INSERT_WORDS(x,hx,lx);
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        return x;
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}
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#endif /* _DOUBLE_IS_32BITS */

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