0dc9e0996a
As the current libc includes a libm implementation, with the new libc this is needed. Unneeded (for the moment) archs have been removed.
125 lines
3.4 KiB
Groff
125 lines
3.4 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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.\" 3. 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: @(#)hypot.3 6.7 (Berkeley) 5/6/91
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.\" $NetBSD: hypot.3,v 1.17 2007/02/22 22:08:20 drochner Exp $
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.\"
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.Dd February 12, 2007
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.Dt HYPOT 3
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.Os
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.Sh NAME
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.Nm hypot ,
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.Nm hypotf
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.Nd Euclidean distance and complex absolute value functions
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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 hypot "double x" "double y"
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.Ft float
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.Fn hypotf "float x" "float y"
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.Sh DESCRIPTION
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The
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.Fn hypot
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functions
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compute the
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sqrt(x*x+y*y)
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in such a way that underflow will not happen, and overflow
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occurs only if the final result deserves it.
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.Pp
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.Fn hypot "\*(If" "v"
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=
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.Fn hypot "v" "\*(If"
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= +\*(If for all
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.Ar v ,
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including \*(Na.
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.Sh ERRORS
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Below 0.97
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.Em ulps .
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Consequently
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.Fn hypot "5.0" "12.0"
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= 13.0
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exactly;
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in general, hypot returns an integer whenever an
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integer might be expected.
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.Pp
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The same cannot be said for the shorter and faster version of hypot
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that is provided in the comments in cabs.c; its error can
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exceed 1.2
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.Em ulps .
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.Sh NOTES
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As might be expected,
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.Fn hypot "v" "\*(Na"
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and
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.Fn hypot "\*(Na" "v"
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are \*(Na for all
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.Em finite
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.Ar v ;
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with "reserved operand" in place of "\*(Na", the
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same is true on a
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.Tn VAX .
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But programmers on machines other than a
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.Tn VAX
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(it has no \*(If)
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might be surprised at first to discover that
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.Fn hypot "\(+-\*(If" "\*(Na"
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= +\*(If.
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This is intentional; it happens because
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.Fn hypot "\*(If" "v"
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= +\*(If
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for
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.Em all
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.Ar v ,
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finite or infinite.
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Hence
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.Fn hypot "\*(If" "v"
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is independent of
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.Ar v .
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Unlike the reserved operand fault on a
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.Tn VAX ,
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the
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.Tn IEEE
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\*(Na is designed to
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disappear when it turns out to be irrelevant, as it does in
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.Fn hypot "\*(If" "\*(Na" .
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.Sh SEE ALSO
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.Xr math 3 ,
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.Xr sqrt 3
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.Sh HISTORY
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Both a
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.Fn hypot
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function and a
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.Fn cabs
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function
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appeared in
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.At v7 .
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.Fn cabs
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was removed from public namespace in
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.Nx 5.0
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to avoid conflicts with the complex function in C99.
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