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112 lines
2.9 KiB
Groff
112 lines
2.9 KiB
Groff
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.\" $NetBSD: ilogb.3,v 1.3 2011/08/02 10:15:03 wiz Exp $
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.\"
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.\" Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi>
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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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd July 29, 2011
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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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.Nd an unbiased 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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.Sh DESCRIPTION
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The
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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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functions return the exponent of the non-zero real floating-point number
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.Fa x
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as a signed integer value.
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Formally the return value is the integral part of
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.Bd -ragged -offset indent
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log_r |
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.Va x | ,
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.Ed
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.Pp
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where
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.Fa r
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is the radix of the machine's floating-point arithmetic defined by the
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.Dv FLT_RADIX
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constant in
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.In float.h .
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.Sh RETURN VALUES
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As described above, upon successful completion,
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the functions return the exponent.
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Functionally this is the same as calling the corresponding
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.Xr logb 3
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function and casting the return value to
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.Vt int .
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.Pp
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The following special cases may occur:
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.Bl -enum -offset indent
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.It
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If
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.Fa x
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is zero, the value of
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.Dv FP_ILOGB0
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is returned and a domain error occurs.
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.It
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If
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.Fa x
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is infinite, a domain error occurs and the value of
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.Dv INT_MAX
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is returned.
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.It
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If
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.Fa x
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is \*(Na, a domain error is raised and the value of
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.Dv FP_ILOGBNAN
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is returned.
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.It
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If the correct value is outside the range of the return type,
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a domain error occurs but an unspecified value is returned.
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.El
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.Sh SEE ALSO
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.Xr ilog2 3 ,
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.Xr logb 3 ,
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.Xr math 3
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.Sh STANDARDS
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The described functions conform to
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.St -isoC-99 .
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.Sh BUGS
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Neither
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.Dv FP_ILOGB0
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nor
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.Dv FP_ILOGBNAN
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is defined currently in
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.Nx .
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