Implement trunc() and truncf().
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2020-12-20 02:59:44 +00:00
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74
lib/msun/man/trunc.3
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lib/msun/man/trunc.3
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.\" Copyright (c) 2004 David Schultz <das@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd June 20, 2004
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.Dt TRUNC 3
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.Os
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.Sh NAME
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.Nm trunc ,
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.Nm truncf
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.Nd nearest integral value with magnitude less than or equal to |x|
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.Sh LIBRARY
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.Lb libm
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.Sh SYNOPSIS
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.In math.h
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.Ft double
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.Fn trunc "double x"
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.Ft float
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.Fn truncf "float x"
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.Sh DESCRIPTION
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The
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.Fn trunc
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and
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.Fn truncf
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functions return the nearest integral value with magnitude less than
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or equal to
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.Pf | Fa x Ns | .
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They are equivalent to
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.Fn rint
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and
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.Fn rintf ,
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respectively, in the
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.Dv FE_TOWARDZERO
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rounding mode.
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.Sh SEE ALSO
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.Xr ceil 3 ,
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.Xr fesetround 3 ,
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.Xr floor 3 ,
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.Xr math 3 ,
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.Xr nextafter 3 ,
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.Xr rint 3 ,
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.Xr round 3
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.Sh STANDARDS
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The
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.Fn trunc
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and
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.Fn truncf
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functions conform to
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.St -isoC-99 .
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.Sh HISTORY
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These routines first appeared in
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.Fx 5.3 .
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61
lib/msun/src/s_trunc.c
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61
lib/msun/src/s_trunc.c
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/* @(#)s_floor.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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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/*
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* trunc(x)
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* Return x rounded toward 0 to integral value
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* Method:
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* Bit twiddling.
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* Exception:
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* Inexact flag raised if x not equal to trunc(x).
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*/
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#include "math.h"
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#include "math_private.h"
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static const double huge = 1.0e300;
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double
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trunc(double x)
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{
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int32_t i0,i1,j0;
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u_int32_t i,j;
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EXTRACT_WORDS(i0,i1,x);
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j0 = ((i0>>20)&0x7ff)-0x3ff;
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if(j0<20) {
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if(j0<0) { /* raise inexact if x != 0 */
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if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
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i0 &= 0x80000000U;
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i1 = 0;
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}
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} else {
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i = (0x000fffff)>>j0;
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if(((i0&i)|i1)==0) return x; /* x is integral */
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if(huge+x>0.0) { /* raise inexact flag */
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i0 &= (~i); i1=0;
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}
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}
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} else if (j0>51) {
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if(j0==0x400) return x+x; /* inf or NaN */
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else return x; /* x is integral */
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} else {
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i = ((u_int32_t)(0xffffffff))>>(j0-20);
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if((i1&i)==0) return x; /* x is integral */
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if(huge+x>0.0) /* raise inexact flag */
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i1 &= (~i);
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}
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INSERT_WORDS(x,i0,i1);
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return x;
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}
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53
lib/msun/src/s_truncf.c
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53
lib/msun/src/s_truncf.c
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/* @(#)s_floor.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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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/*
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* truncf(x)
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* Return x rounded toward 0 to integral value
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* Method:
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* Bit twiddling.
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* Exception:
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* Inexact flag raised if x not equal to truncf(x).
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*/
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#include "math.h"
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#include "math_private.h"
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static const float huge = 1.0e30F;
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float
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truncf(float x)
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{
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int32_t i0,j0;
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u_int32_t i;
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GET_FLOAT_WORD(i0,x);
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j0 = ((i0>>23)&0xff)-0x7f;
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if(j0<23) {
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if(j0<0) { /* raise inexact if x != 0 */
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if(huge+x>0.0F) /* |x|<1, so return 0*sign(x) */
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i0 &= 0x80000000;
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} else {
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i = (0x007fffff)>>j0;
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if((i0&i)==0) return x; /* x is integral */
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if(huge+x>0.0F) /* raise inexact flag */
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i0 &= (~i);
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}
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} else {
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if(j0==0x80) return x+x; /* inf or NaN */
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else return x; /* x is integral */
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}
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SET_FLOAT_WORD(x,i0);
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return x;
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}
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