HP-UX Reference (11i v1 00/12) - 3 Library Functions A-M (vol 6)
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STANDARD Printed by: Nora Chuang [nchuang] STANDARD
/build/1111/BRICK/man3/!!!intro.3c
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l
log(3M) log(3M)
NAME
log(), logf() - natural logarithm functions
SYNOPSIS
#include <math.h>
double log(double x);
float logf(float x);
DESCRIPTION
log() returns the natural logarithm of x. The value of x must be greater than zero.
logf() is a float version of log(); it takes a float argument and returns a float result. To use
this function, compile either with the default -Ae option or with the -Aa and -D_HPUX_SOURCE options.
logf() is not specified by any standard, but it is named in accordance with the conventions specified in
the "Future Library Directions" section of the ANSI C standard.
To use these functions, make sure your program includes <math.h>, and link in the math library by speci-
fying -lm on the compiler or linker command line.
Millicode versions of the log() and logf() functions are available. Millicode versions of math library
functions are usually faster than their counterparts in the standard library. To use these versions, compile
your program with the
+Olibcalls or the +Oaggressive optimization option.
If an error occurs, the millicode versions return the value described in the RETURN VALUE section, but do
not set errno.
For more information, see the HP-UX Floating-Point Guide.
RETURN VALUE
If x is +INFINITY,
log() returns +INFINITY.
If x is zero,
log() returns −HUGE_VAL.
If x is NaN, log() returns NaN.
If x is less than zero, log() returns NaN and sets errno to [EDOM].
ERRORS
If log() fails, errno is set to the following value.
[EDOM] x is less than zero.
SEE ALSO
cbrt(3M), exp(3M), log10(3M), log1p(3M), log2(3M), pow(3M), sqrt(3M), math(5).
STANDARDS CONFORMANCE
log(): SVID3, XPG4.2, ANSI C
HP-UX Release 11i: December 2000 − 1 − Section 3−−495
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