log.3 revision 1.1
$NetBSD: log.3,v 1.1 2011/09/13 05:26:47 jruoho Exp $
Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi>
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
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1. Redistributions of source code must retain the above copyright
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THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.Dd September 13, 2011 .Dt SCALBN 3 .Os .Sh NAME .Nm log , .Nm logf , .Nm log10 , .Nm log10f , .Nm log1p , .Nm log1pf .Nm log2 , .Nm log2f , .Nd logarithm functions .Sh LIBRARY .Lb libm .Sh SYNOPSIS n math.h .Ft double .Fn log "double x" .Ft float .Fn logf "float x" .Ft double .Fn log10 "double x" .Ft float .Fn log10f "float x" .Ft double .Fn log1p "double x" .Ft float .Fn log1pf "float x" .Ft double .Fn log2 "double x" .Ft float .Fn log2f "float x" .Sh DESCRIPTION The following functions compute logarithms: l -bullet -offset 2n t The .Fn log and .Fn logf functions return the natural logarithm. t The .Fn log10 and .Fn log10f functions return the base 10 logarithm. t The .Fn log1p and .Fn log1pf functions return the natural logarithm of (1.0 + .Fa x ) accurately even for very small values of .Fa x . t The .Fn log2 and .Fn log2f functions return the base 2 logarithm. .Sh RETURN VALUES Upon successful completion, the functions return the logarithm of .Fa x as descibed above. Otherwise the following may occur: l -enum -offset indent t If .Fa x is \*(Na, all functions return \*(Na. t If .Fa x is positive infinity, all functions return .Fa x . If .Fa x is negative infinity, all functions return \*(Na. t If .Fa x is +0.0 or -0.0, the .Fn log , .Fn log10 , and .Fn log2 families return either .Dv -HUGE_VAL , .Dv -HUGE_VALF , or .Dv -HUGE_VALL , whereas the .Fn log1p family returns .Fa x . t If .Fa x is +1.0, the .Fn log , .Fn log10 , and .Fn log2 families return +0.0. If .Fa x is -1.0, the .Fn log1p family returns .Dv -HUGE_VAL , .Dv -HUGE_VALF , or .Dv -HUGE_VALL . .El
Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi>
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
.Dd September 13, 2011 .Dt SCALBN 3 .Os .Sh NAME .Nm log , .Nm logf , .Nm log10 , .Nm log10f , .Nm log1p , .Nm log1pf .Nm log2 , .Nm log2f , .Nd logarithm functions .Sh LIBRARY .Lb libm .Sh SYNOPSIS n math.h .Ft double .Fn log "double x" .Ft float .Fn logf "float x" .Ft double .Fn log10 "double x" .Ft float .Fn log10f "float x" .Ft double .Fn log1p "double x" .Ft float .Fn log1pf "float x" .Ft double .Fn log2 "double x" .Ft float .Fn log2f "float x" .Sh DESCRIPTION The following functions compute logarithms: l -bullet -offset 2n t The .Fn log and .Fn logf functions return the natural logarithm. t The .Fn log10 and .Fn log10f functions return the base 10 logarithm. t The .Fn log1p and .Fn log1pf functions return the natural logarithm of (1.0 + .Fa x ) accurately even for very small values of .Fa x . t The .Fn log2 and .Fn log2f functions return the base 2 logarithm. .Sh RETURN VALUES Upon successful completion, the functions return the logarithm of .Fa x as descibed above. Otherwise the following may occur: l -enum -offset indent t If .Fa x is \*(Na, all functions return \*(Na. t If .Fa x is positive infinity, all functions return .Fa x . If .Fa x is negative infinity, all functions return \*(Na. t If .Fa x is +0.0 or -0.0, the .Fn log , .Fn log10 , and .Fn log2 families return either .Dv -HUGE_VAL , .Dv -HUGE_VALF , or .Dv -HUGE_VALL , whereas the .Fn log1p family returns .Fa x . t If .Fa x is +1.0, the .Fn log , .Fn log10 , and .Fn log2 families return +0.0. If .Fa x is -1.0, the .Fn log1p family returns .Dv -HUGE_VAL , .Dv -HUGE_VALF , or .Dv -HUGE_VALL . .El
p In addition, on a .Tn VAX , .Va errno is set to .Er EDOM and the reserved operand is returned by .Fn log unless .Fa x \*[Gt] 0, by .Fn log1p unless .Fa x \*[Gt] -1. .Sh SEE ALSO .Xr exp 3 , .Xr ilogb 3 , .Xr math 3 .Sh STANDARDS The described functions conform to .St -isoC-99 . .Sh HISTORY The history of the logarithm functions dates back to .At v6 .