NAME

log10(), log10f() − common logarithm functions

SYNOPSIS

#include <math.h>

double log10(double x);

float log10f(float x);

DESCRIPTION

log10() returns the logarithm base ten of x. The value of x must be positive. 

log10f() is a float version of log10(); it takes a float argument and returns a float result.  To use this function, compile either with the −Ae option or with the −Aa and −D_HPUX_SOURCE options.  Otherwise, the compiler promotes the float argument to double, and the function returns incorrect results. 

log10f() 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, link in the math library by specifying −lm on the compiler or linker command line. 

RETURN VALUE

If x is +INFINITY, log10() returns +INFINITY. 

If x is zero, log10() returns −HUGE_VAL. 

If x is NaN, log10() returns NaN. 

If x is negative, log10() returns NaN and sets errno to [EDOM]. 

ERRORS

If log10() fails, errno is set to the following value. 

[EDOM] x is negative. 

DEPENDENCIES

Millicode versions of the log10() function are available on PA1.1-based and PA2.0-based systems, in the library /usr/lib/milli.a.  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 +DA1.1 option (the default on PA1.1-based systems) or the +DA2.0 option (the default on PA2.0-based systems) and 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.

SEE ALSO

exp(3M), log(3M), log2(3M), pow(3M), sqrt(3M), cbrt(3M), isinf(3M), isnan(3M). 

STANDARDS CONFORMANCE

log10(): SVID3, XPG4.2, ANSI C

Hewlett-Packard Company  —  HP-UX Release 10.20:  July 1996