lib/libm/src/s_nextafterf.c

   1 /* s_nextafterf.c -- float version of s_nextafter.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #include <sys/cdefs.h>
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 __RCSID("$NetBSD: s_nextafterf.c,v 1.6 1999/07/02 15:37:43 simonb Exp $");
  19 #endif
  20
  21 #include "math.h"
  22 #include "math_private.h"
  23
  24 float
  25 nextafterf(float x, float y)
  26 {
  27         int32_t hx,hy,ix,iy;
  28
  29         GET_FLOAT_WORD(hx,x);
  30         GET_FLOAT_WORD(hy,y);
  31         ix = hx&0x7fffffff;             /* |x| */
  32         iy = hy&0x7fffffff;             /* |y| */
  33
  34         if((ix>0x7f800000) ||   /* x is nan */
  35            (iy>0x7f800000))     /* y is nan */
  36            return x+y;
  37         if(x==y) return x;              /* x=y, return x */
  38         if(ix==0) {                             /* x == 0 */
  39             SET_FLOAT_WORD(x,(hy&0x80000000)|1);/* return +-minsubnormal */
  40             y = x*x;
  41             if(y==x) return y; else return x;   /* raise underflow flag */
  42         }
  43         if(hx>=0) {                             /* x > 0 */
  44             if(hx>hy) {                         /* x > y, x -= ulp */
  45                 hx -= 1;
  46             } else {                            /* x < y, x += ulp */
  47                 hx += 1;
  48             }
  49         } else {                                /* x < 0 */
  50             if(hy>=0||hx>hy){                   /* x < y, x -= ulp */
  51                 hx -= 1;
  52             } else {                            /* x > y, x += ulp */
  53                 hx += 1;
  54             }
  55         }
  56         hy = hx&0x7f800000;
  57         if(hy>=0x7f800000) return x+x;  /* overflow  */
  58         if(hy<0x00800000) {             /* underflow */
  59             y = x*x;
  60             if(y!=x) {          /* raise underflow flag */
  61                 SET_FLOAT_WORD(y,hx);
  62                 return y;
  63             }
  64         }
  65         SET_FLOAT_WORD(x,hx);
  66         return x;
  67 }