138 lines
3.1 KiB
Groff
138 lines
3.1 KiB
Groff
.\" Copyright (c) 2008-2010 David Schultz <das@FreeBSD.org>
|
|
.\" 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 AUTHOR 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 AUTHOR 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.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd June 3, 2013
|
|
.Dt LOG 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm log ,
|
|
.Nm logf ,
|
|
.Nm logl ,
|
|
.Nm log10 ,
|
|
.Nm log10f ,
|
|
.Nm log10l ,
|
|
.Nm log2 ,
|
|
.Nm log2f ,
|
|
.Nm log2l ,
|
|
.Nm log1p ,
|
|
.Nm log1pf ,
|
|
.Nm log1pl
|
|
.Nd logarithm functions
|
|
.Sh LIBRARY
|
|
.Lb libm
|
|
.Sh SYNOPSIS
|
|
.In math.h
|
|
.Ft double
|
|
.Fn log "double x"
|
|
.Ft float
|
|
.Fn logf "float x"
|
|
.Ft long double
|
|
.Fn logl "long double x"
|
|
.Ft double
|
|
.Fn log10 "double x"
|
|
.Ft float
|
|
.Fn log10f "float x"
|
|
.Ft long double
|
|
.Fn log10l "long double x"
|
|
.Ft double
|
|
.Fn log2 "double x"
|
|
.Ft float
|
|
.Fn log2f "float x"
|
|
.Ft long double
|
|
.Fn log2l "long double x"
|
|
.Ft double
|
|
.Fn log1p "double x"
|
|
.Ft float
|
|
.Fn log1pf "float x"
|
|
.Ft long double
|
|
.Fn log1pl "long double x"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn log ,
|
|
.Fn logf ,
|
|
and
|
|
.Fn logl
|
|
functions compute the natural logarithm of
|
|
.Fa x .
|
|
.Pp
|
|
The
|
|
.Fn log10 ,
|
|
.Fn log10f ,
|
|
and
|
|
.Fn log10l
|
|
functions compute the logarithm base 10 of
|
|
.Fa x ,
|
|
while
|
|
.Fn log2 ,
|
|
.Fn log2f ,
|
|
and
|
|
.Fn log2l
|
|
compute the logarithm base 2 of
|
|
.Fa x .
|
|
.Pp
|
|
The
|
|
.Fn log1p ,
|
|
.Fn log1pf ,
|
|
and
|
|
.Fn log1pl
|
|
functions compute the natural logarithm of
|
|
.No "1 + x" .
|
|
Computing the natural logarithm as
|
|
.Li log1p(x)
|
|
is more accurate than computing it as
|
|
.Li log(1 + x)
|
|
when
|
|
.Fa x
|
|
is close to zero.
|
|
.Sh RETURN VALUES
|
|
These functions return the requested logarithm; the logarithm of 1 is +0.
|
|
An attempt to take the logarithm of \*(Pm0 results in a divide-by-zero
|
|
exception, and -\*(If is returned.
|
|
Otherwise, attempting to take the logarithm of a negative number
|
|
results in an invalid exception and a return value of \*(Na.
|
|
.Sh SEE ALSO
|
|
.Xr exp 3 ,
|
|
.Xr ilogb 3 ,
|
|
.Xr math 3 ,
|
|
.Xr pow 3
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn log ,
|
|
.Fn logf ,
|
|
.Fn logl ,
|
|
.Fn log10 ,
|
|
.Fn log10f ,
|
|
.Fn log10l ,
|
|
.Fn log2 ,
|
|
.Fn log2f ,
|
|
.Fn log2l ,
|
|
.Fn log1p ,
|
|
.Fn log1pf ,
|
|
and
|
|
.Fn log1pl
|
|
functions conform to
|
|
.St -isoC-99 .
|