125 lines
2.9 KiB
Groff
125 lines
2.9 KiB
Groff
.\" Copyright (c) 1985, 1991 Regents of the University of California.
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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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.\" 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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.\" from: @(#)ieee.3 6.4 (Berkeley) 5/6/91
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.\" $FreeBSD$
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.\"
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.Dd December 16, 2007
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.Dt ILOGB 3
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.Os
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.Sh NAME
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.Nm ilogb ,
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.Nm ilogbf ,
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.Nm ilogbl ,
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.Nm logb ,
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.Nm logbf ,
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.Nm logbl
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.Nd extract exponent
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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 int
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.Fn ilogb "double x"
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.Ft int
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.Fn ilogbf "float x"
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.Ft int
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.Fn ilogbl "long double x"
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.Ft double
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.Fn logb "double x"
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.Ft float
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.Fn logbf "float x"
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.Ft long double
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.Fn logbl "long double x"
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.Sh DESCRIPTION
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.Fn ilogb ,
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.Fn ilogbf
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and
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.Fn ilogbl
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return
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.Fa x Ns 's exponent
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in integer format.
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.Fn ilogb \*(Pm\*(If
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returns
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.Dv INT_MAX ,
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.Fn ilogb \*(Pm\*(Na
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returns
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.Dv FP_ILOGBNAN ,
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and
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.Fn ilogb 0
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returns
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.Dv FP_ILOGB0 .
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.Pp
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.Fn logb x ,
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.Fn logbf x ,
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and
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.Fn logbl x
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return
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.Fa x Ns 's exponent
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in floating\-point format with the same precision as
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.Fa x .
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.Fn logb \*(Pm\*(If
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returns +\*(If, and
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.Fn logb 0
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returns -\*(If with a division by zero exception.
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.Sh SEE ALSO
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.Xr frexp 3 ,
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.Xr ieee 3 ,
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.Xr math 3 ,
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.Xr scalbn 3
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.Sh STANDARDS
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The
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.Fn ilogb ,
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.Fn ilogbf ,
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.Fn ilogbl ,
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.Fn logb ,
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.Fn logbf ,
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and
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.Fn logbl
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routines conform to
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.St -isoC-99 .
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The latter three
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implement the logb function recommended by
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.St -ieee754 .
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.Sh HISTORY
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.Bl -tag -width "Function " -compact
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.It Em Function
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.Em "First Appeared In"
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.It Fn logb
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.Bx 4.3
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.It Fn ilogb
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.Fx 1.1.5
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.It Fn ilogbf
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.Fx 2.0
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.It Fn logbf
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.Fx 2.0
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.It Fn ilogbl
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.Fx 5.4
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.It Fn logbl
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.Fx 8.0
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.El
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