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| 2 | /* @(#)e_remainder.c 5.1 93/09/24 */ |
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| 3 | /* |
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| 4 | * ==================================================== |
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| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 6 | * |
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| 7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 8 | * Permission to use, copy, modify, and distribute this |
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| 9 | * software is freely granted, provided that this notice |
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| 10 | * is preserved. |
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| 11 | * ==================================================== |
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| 12 | */ |
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| 13 | |
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| 14 | /* |
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| 15 | FUNCTION |
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| 16 | <<remainder>>, <<remainderf>>---round and remainder |
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| 17 | INDEX |
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| 18 | remainder |
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| 19 | INDEX |
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| 20 | remainderf |
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| 21 | |
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| 22 | SYNOPSIS |
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| 23 | #include <math.h> |
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| 24 | double remainder(double <[x]>, double <[y]>); |
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| 25 | float remainderf(float <[x]>, float <[y]>); |
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| 26 | |
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| 27 | DESCRIPTION |
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| 28 | <<remainder>> and <<remainderf>> find the remainder of |
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| 29 | <[x]>/<[y]>; this value is in the range -<[y]>/2 .. +<[y]>/2. |
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| 30 | |
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| 31 | RETURNS |
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| 32 | <<remainder>> returns the integer result as a double. |
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| 33 | |
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| 34 | PORTABILITY |
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| 35 | <<remainder>> is a System V release 4. |
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| 36 | <<remainderf>> is an extension. |
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| 37 | |
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| 38 | */ |
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| 39 | |
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| 40 | /* remainder(x,p) |
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| 41 | * Return : |
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| 42 | * returns x REM p = x - [x/p]*p as if in infinite |
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| 43 | * precise arithmetic, where [x/p] is the (infinite bit) |
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| 44 | * integer nearest x/p (in half way case choose the even one). |
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| 45 | * Method : |
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| 46 | * Based on fmod() return x-[x/p]chopped*p exactlp. |
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| 47 | */ |
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| 48 | |
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| 49 | #include "fdlibm.h" |
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| 50 | |
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| 51 | #ifndef _DOUBLE_IS_32BITS |
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| 52 | |
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| 53 | #ifdef __STDC__ |
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| 54 | static const double zero = 0.0; |
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| 55 | #else |
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| 56 | static double zero = 0.0; |
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| 57 | #endif |
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| 58 | |
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| 59 | |
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| 60 | #ifdef __STDC__ |
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| 61 | double remainder(double x, double p) |
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| 62 | #else |
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| 63 | double remainder(x,p) |
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| 64 | double x,p; |
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| 65 | #endif |
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| 66 | { |
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| 67 | __int32_t hx,hp; |
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| 68 | __uint32_t sx,lx,lp; |
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| 69 | double p_half; |
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| 70 | |
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| 71 | EXTRACT_WORDS(hx,lx,x); |
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| 72 | EXTRACT_WORDS(hp,lp,p); |
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| 73 | sx = hx&0x80000000; |
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| 74 | hp &= 0x7fffffff; |
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| 75 | hx &= 0x7fffffff; |
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| 76 | |
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| 77 | /* purge off exception values */ |
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| 78 | if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */ |
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| 79 | if((hx>=0x7ff00000)|| /* x not finite */ |
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| 80 | ((hp>=0x7ff00000)&& /* p is NaN */ |
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| 81 | (((hp-0x7ff00000)|lp)!=0))) |
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| 82 | return (x*p)/(x*p); |
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| 83 | |
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| 84 | |
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| 85 | if (hp<=0x7fdfffff) x = fmod(x,p+p); /* now x < 2p */ |
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| 86 | if (((hx-hp)|(lx-lp))==0) return zero*x; |
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| 87 | x = fabs(x); |
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| 88 | p = fabs(p); |
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| 89 | if (hp<0x00200000) { |
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| 90 | if(x+x>p) { |
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| 91 | x-=p; |
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| 92 | if(x+x>=p) x -= p; |
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| 93 | } |
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| 94 | } else { |
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| 95 | p_half = 0.5*p; |
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| 96 | if(x>p_half) { |
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| 97 | x-=p; |
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| 98 | if(x>=p_half) x -= p; |
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| 99 | } |
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| 100 | } |
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| 101 | GET_HIGH_WORD(hx,x); |
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| 102 | SET_HIGH_WORD(x,hx^sx); |
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| 103 | return x; |
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| 104 | } |
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| 105 | |
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| 106 | #endif /* defined(_DOUBLE_IS_32BITS) */ |
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