165 lines
4.7 KiB
Groff
165 lines
4.7 KiB
Groff
.\" Copyright (c) 1993 Andrew Moore, Talke Studio
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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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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.\" @(#)fpgetround.3 1.0 (Berkeley) 9/23/93
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.\" $FreeBSD$
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.\"
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.Dd August 23, 1993
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.Dt FPGETROUND 3
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.Os
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.Sh NAME
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.Nm fpgetround ,
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.Nm fpsetround ,
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.Nm fpsetprec ,
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.Nm fpgetprec ,
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.Nm fpgetmask ,
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.Nm fpsetmask ,
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.Nm fpgetsticky ,
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.Nm fpresetsticky
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.Nd IEEE floating point interface
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.Sh SYNOPSIS
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.Fd #include <ieeefp.h>
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.Pp
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.Bd -literal
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typedef enum {
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FP_RN, /* round to nearest */
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FP_RM, /* round down to minus infinity */
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FP_RP, /* round up to plus infinity */
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FP_RZ /* truncate */
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} fp_rnd_t;
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.Ed
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.Ft fp_rnd_t
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.Fn fpgetround void
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.Ft fp_rnd_t
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.Fn fpsetround "fp_rnd_t direction"
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.Pp
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.Bd -literal
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typedef enum {
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FP_PS, /* 24 bit (single-precision) */
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FP_PRS, /* reserved */
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FP_PD, /* 53 bit (double-precision) */
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FP_PE /* 64 bit (extended-precision) */
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} fp_prec_t;
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.Ed
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.Ft fp_prec_t
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.Fn fpgetprec void
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.Ft fp_prec_t
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.Fn fpsetprec "fp_prec_t precision"
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.Pp
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.Bd -literal
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#define fp_except_t int
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#define FP_X_INV 0x01 /* invalid operation */
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#define FP_X_DNML 0x02 /* denormal */
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#define FP_X_DZ 0x04 /* zero divide */
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#define FP_X_OFL 0x08 /* overflow */
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#define FP_X_UFL 0x10 /* underflow */
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#define FP_X_IMP 0x20 /* (im)precision */
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#define FP_X_STK 0x40 /* stack fault */
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.Ed
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.Ft fp_except_t
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.Fn fpgetmask void
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.Ft fp_except_t
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.Fn fpsetmask "fp_except_t mask"
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.Ft fp_except_t
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.Fn fpgetsticky void
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.Ft fp_except_t
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.Fn fpresetsticky "fp_except_t sticky"
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.Sh DESCRIPTION
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When a floating point exception is detected, the exception sticky flag is
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set and the exception mask is tested.
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If the mask is set, then a trap
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occurs. These routines allow both setting the floating point exception
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masks, and resetting the exception sticky flags after an exception is
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detected. In addition, they allow setting the floating point rounding mode
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and precision.
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.Pp
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The
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.Fn fpgetround
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function
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returns the current floating point rounding mode.
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.Pp
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The
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.Fn fpsetround
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function
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sets the floating point rounding mode and returns
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the previous mode.
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.Pp
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The
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.Fn fpgetprec
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function
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returns the current floating point precision.
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.Pp
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The
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.Fn fpsetprec
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function
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sets the floating point precision and returns
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the previous precision.
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.Pp
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The
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.Fn fpgetmask
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function
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returns the current floating point exception masks.
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.Pp
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The
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.Fn fpsetmask
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function
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sets the floating point exception masks and returns the
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previous masks.
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.Pp
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The
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.Fn fpgetsticky
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function
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returns the current floating point sticky flags.
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.Pp
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The
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.Fn fpresetsticky
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function
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clears the floating point sticky flags and returns
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the previous flags.
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.Pp
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Sample code which prevents a trap on divide-by-zero:
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.Bd -literal -offset indent
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fpsetmask(~FP_X_DZ);
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a = 1.0;
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b = 0;
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c = a / b;
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fpresetsticky(FP_X_DZ);
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fpsetmask(FP_X_DZ);
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.Ed
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.Sh SEE ALSO
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.Xr isnan 3
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.Sh CAVEAT
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After a floating point exception and before a mask is set, the sticky
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flags must be reset. If another exception occurs before the sticky
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flags are reset, then a wrong exception type may be signaled.
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.Sh HISTORY
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These routines are based on SysV/386 routines of the same name.
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